Front Cover
 Title Page
 Executive summary
 Table of Contents
 List of Tables
 List of Figures
 1. Introduction to playa chara...
 2. Playa regional geography
 3. Playa basin environment
 4. Ecology of playa basins
 5. Playa uses and modification
 6. Impacts on playa wildlife...
 Cited references
 Appendix A. Plants of playas in...
 Appendix B. Birds of playas in...
 Appendix C. Mammals of playas in...
 Appendix D. Amphibians, reptiles,...
 Appendix E. Invertebrates of playas...
 Back Matter
 Back Cover

Group Title: Playa wetlands and wildlife on the Southern Great Plains : a characterization of habitat
Title: Playa wetlands and wildlife on the Southern Great Plains
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00014885/00001
 Material Information
Title: Playa wetlands and wildlife on the Southern Great Plains a characterization of habitat
Physical Description: xvi, 163 p. : ill., maps ; 28 cm.
Language: English
Creator: Nelson, R. Wayne
Weller, Emily C
Logan, William J
Western Energy and Land Use Team
United States -- Environmental Protection Agency
Publisher: The Team
Place of Publication: Washington DC
Publication Date: 1984
Subject: Wetland ecology -- United States   ( lcsh )
Wildlife habitat improvement -- United States   ( lcsh )
Tailwater ecology -- United States   ( lcsh )
Playas -- United States   ( lcsh )
Genre: federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Summary: The Southern Great Plains playa wildlife study region is divided to cover five states where playa lakes and wetlands are common features in their landscapes. Playas are critically important to resident wildlife in this dry farmland region where any moist or aquatic habitat is extremely scarce. This study is aimed to portray current knowledge as a basis for new effects at habitat preservation and management of playas for multiple use including wildlife management.
Bibliography: Bibliography: p. 139-146.
Statement of Responsibility: by R. Wayne Nelson, William J. Logan, Emily C. Weller ; performed for Western Energy and Land Use Team, Division of Biological Services, Research and Development, Fish and Wildlife Service, U.S. Department of the Interior.
General Note: "September 1983."
General Note: "In cooperation with U.S. Environmental Protection Agency"--Cover.
General Note: "FWS/OBS-83/28."
General Note: Distributed to depository libraries in microfiche.
 Record Information
Bibliographic ID: UF00014885
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: notis - AAA7198
oclc - 52863518
 Related Items
Other version: Alternate version (PALMM)
PALMM Version

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Title Page
        Title Page 1
        Title Page 2
        Page i
        Page ii
    Executive summary
        Page iii
        Page iv
        Page v
        Page vi
    Table of Contents
        Page vii
        Page viii
        Page ix
        Page x
    List of Tables
        Page xi
        Page xii
    List of Figures
        Page xiii
        Page xiv
        Page xv
        Page xvi
    1. Introduction to playa characterization
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    2. Playa regional geography
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
    3. Playa basin environment
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
    4. Ecology of playa basins
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
    5. Playa uses and modification
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
        Page 121
        Page 122
    6. Impacts on playa wildlife habitat
        Page 123
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
    Cited references
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
    Appendix A. Plants of playas in the Llano Estacado
        Page 147
        Page 148
        Page 149
        Page 150
        Page 151
        Page 152
    Appendix B. Birds of playas in the Llano Estacado
        Page 153
        Page 154
        Page 155
        Page 156
        Page 157
        Page 158
    Appendix C. Mammals of playas in the Llano Estacado
        Page 159
        Page 160
    Appendix D. Amphibians, reptiles, and fishes of playas in the Llano Estacado
        Page 161
        Page 162
    Appendix E. Invertebrates of playas in the Llano Estacado
        Page 163
    Back Matter
        Page 164
    Back Cover
        Back Cover 1
        Back Cover 2
Full Text




-I -
L_- ~~ -.-,
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VX -Ar

Fish and Wildlife Service

'In cooperation with
U.S. Environmental Protection Agency

U.S. Department of the Interior

r"^N E ',


A related publication on playa wetlands is also available from the U.S.
Fish and Wildlife Service: I
Playa wetlands and wildlife on the Southern Great Plains: A guide to
habitat management. FWS/OBS-83/29. I


September 1983

A Characterization of Habitat


R. Wayne Nelson
William J. Logan
Emily C. Weller

R. Wayne Nelson and Associates, Inc.
275 Spruce Court
Boulder, Colorado 80302

Performed for

Western Energy and Land Use Team
Division of Biological Services
Research and Development
Fish and Wildlife Service
U.S. Department of the Interior
Washington, DC 20240

This report should be cited as:

Nelson, R.W, W.J. Logan, and E.C. Weller. 1983. Playa wetlands and wildlife on the Southern
Great Plains: A characterization of habitat. U.S. Fish Wildl. Serv. FWSIOBS-83/28. 163 pp.


Funding for this playa study was pro-
vided by the Office of Federal Activities,
U.S. Environmental Protection Agency and
the Fish and Wildlife Service's Regional
Office in Albuquerque, New Mexico. Charles
A. Segelquist, Division of Biological Ser-
vices, U.S. Fish and Wildlife Service, was
the Project Officer for the study. Other
Fish and Wildlife Service guidance was
provided by Harold Beierman in Fort Worth
(Ecological Services); Warren Hagenbuck in
Albuquerque (National Wetland Inventory);
Charlie Ault in Albuquerque (Ecological
Services); and Edward Flickinger in Victoria,
Texas (Environmental Contaminant Eval-

In the Bureau of Reclamation, Robert
Hanson and Gerald Teter at the Engineering
and Research Center in Denver provided
valuable remote sensing data from the
Bureau's Playa Inventory; Jim Rogers in
Amarillo (Southwest Region) was helpful
as well.

In the Forest Service, Fred Stormer and
Patricia Chamberlain at the Great Plains
Wildlife Research Laboratory in Lubbock
(Texas Tech University) provided some

guidance. Bill Zeedyke in Albuquerque,
Alton Bryant at Kiowa National Grasslands
in New Mexico, and Glen Reagan at Rita
Blanca National Grasslands in Texas con-
tributed some information. Other Federal
contributors included Linda Rondell in
Roswell, New Mexico (Bureau of Land Man-
agement), and George Keeler in Ada,
Oklahoma (Environmental Protection

In the Texas Parks and Wildlife Depart-
ment, Dennis Palafox in Austin, Chris
Wheaton in Canyon, and Dave Dvorak in
Clarendon were helpful. Wayne Wyatt with
the High Plains Underground Water Con-
servation District in Lubbock offered

Dr. Fred S. Guthery, Department of
Range and Wildlife Management, Texas
Tech University (Lubbock), was the princi-
pal advisor to the study team. Lori Hight
of Nelson and Associates in Boulder, Colo-
rado, developed or adapted the maps and
other illustrations; Esther Goodyear pro-
vided the word processing service; and
Patrice Braverman composed the report.


The Southern Great Plains playa wetland
region encompasses the Llano Estacado
(Southern High Plains) of the Texas Panhandle
and adjacent eastern New Mexico, and extends
north of the Canadian River through the
Oklahoma Panhandle into southwest Kansas
and southeast Colorado. For study purposes,
the region is partitioned into five zones having
distinct land use, hydrologic, and soil charac-
teristics. Because high-value playa wildlife
habitat concentrates in one zone (Irrigated
Cropland) near the center of the study region,
most wildlife studies from which the habitat
characterization is drawn will pertain to this
zone. Every effort is made to show the
environmental differences in other zones so
varying habitat values may be inferred.

Although playa habitat is well known for
its importance to migratory waterfowl in the
Central Flyway, its value to resident wildlife
is even more pronounced since wetlands are
so scarce in this dry farmland region. The
characterization incorporates recent research
findings in a synthesis of knowledge about the
habitat values of playa wetlands.


Playas are either ephemeral or perma-
nent lakes or wetlands, depending on the
water depth and persistence, and on the
presence of aquatic vegetation. Under the
National Wetland Classification System, all
playas are classified as palustrine or lacustrine
wetlands. A variety of theories have been
advanced to explain the origin of playas.
There are approximately 25,000 playas within
the 68,500-mi2 (177,400-km2) Southern Great
Plains playa region, with an average surface
density generally under 20 ac/mi2 (about
3 ha/km2 or 3% of land surface). The
majority of playa basins are under 10ac
(4 ha), but they range as high as 600 ac
(240 ha) covering the area of wetland soils.
During a wet season, the average water surface
density may be as high as 4 ac/mi2
(2/3 ha/km2) in the Irrigated Cropland

Zone, but less than 0.2 ac/mi2 (0.03 ha/km2)
in a dry season.

The semiarid regional climate varies from
dry steppe to warm temperate, with annual
precipitation averaging 15-22 in (38-56 cm),
and mean annual evaporation of about 100 in
(254 cm). The main geologic feature is the
Ogallala Aquifer which supplies irrigation
water often collected in playas, enhancing
aquatic habitat, particularly in the west-
central Texas Panhandle. Soils range from fine
sand to silty clay loam, the latter associated
with larger, shallower playas. Most of the
study region is smooth plains and shortgrass
prairie with production of grains, cotton,
cattle, oil and gas as the primary land uses.


The physical environment of playas is
characterized by distinctive soil-water rela-
tionships. Soils are generally clays that form a
highly impermeable seal, thereby increasing
playa water-holding capacity. This feature
promotes their use and modification for
collection and recycling of irrigation tail-
water, while also enhancing scarce wetland
wildlife habitat. Soil texture and percolation
vary significantly north and south through the
playa region; water retention is maximum in
the fine-texture area of the west-central Texas
Panhandle. This area also has a higher average
playa surface density, and irrigated farmland
concentrates here.

Water ordinarily accumulates in un-
modified playas during late spring and
gradually subsides through the summer.
Playas modified to store and reuse irrigation
tailwater will sustain a larger water surface or
volume over a longer period. Most water
contained in unmodified playas and not used
in irrigation is lost by evaporation before
winter. Water quality in unmodified fresh-
water playas is generally uniform and suitable
for irrigation as well as fish and wildlife
habitats; saline playas have limited value.


Variables affecting the value of playa
wildlife habitat may include watershed size
and the water surface area and depth; type,
height, density, and interspersion of vegeta-
tion, and the extent of emergent vegetation;
land use, particularly grazing and cultivation;
and the extent of modification, particularly
excavation and diking. There is considerable
variation in annual precipitation and runoff
and, therefore, in habitat values, especially for
wildlife populations linked with the aquatic
environment. Larger playas that collect irriga-
tion tailwater and are not cultivated or heavily
grazed appear to provide the best wildlife
cover-vegetation that is tall, dense, diverse,
and persistent. Those playas modified to con-
cencentrate water can sustain more open water
and emergent vegetation during dry years.

Cropland playas containing fresh open
water provide valuable waterfowl loafing,
roosting, watering, and foraging sites adjacent
to grain fields used for feeding. Even without
open water, playa wetlands provide important
winter cover for upland game birds, raptors,
and passerines. Playas offer valuable nesting
cover for pheasant and some species of ducks.
Coyotes, raccoons, rabbits, ground squirrels,
and mice are among the abundant mammals
at playa basins. Salamanders and frogs as well
as snakes, lizards and turtles are found among
the indigenous amphibians and reptiles; most
fish populations are introduced. Invertebrates
important in the food chain include grass-
hoppers, fairy shrimp, and snails. Playa
habitats also may promote a number of
diseases in wildlife-encephalitis, avian
cholera, botulism, and duck schistosomiasis.


The impoundment of natural runoff in
playa basins during a wet year may reach the
equivalent of all groundwater pumped
annually from the Ogallala Aquifer in the
Southern Great Plains. However, the accumu-
lation of runoff, particularly in a dry year,
may not coincide with optimum irrigation

scheduling; stored water may evaporate and
seep from playas before it is needed. There-
fore, the practical use of playa water for
irrigation would require basin modifications
such as excavation and diking to concentrate
water storage and reduce evaporation. Many
irrigated cropland playas, particularly the
larger ones, also receive irrigation runoff
(tailwater) which is recycled; most of these
basins have been altered to reduce evapora-
tion. However, current efforts at water
conservation, such as conversion to low-
pressure aerial spraying, are expected to
greatly reduce tailwater.

Many farmers plant crops into the
margins of playas or, in smaller basins less
subject to flooding and crop failure, cultivate
the entire playa. Year-round grazing at
rangeland playas is widespread; many larger
cropland playas are grazed between harvest
and planting. Numerous playa basins are
modified to concentrate water for livestock
use. Some playas are used for disposal of
feedlot waste, but recycling of untreated
feedlot runoff for irrigation could lead to
groundwater pollution. Disposal of oil field
brine in playas can contaminate surface and
groundwater with salt, hydrocarbons, and
other accumulations.

Hunting for pheasants, ducks, geese and
cranes is the main recreational use of playas.
Pheasants congregate at cropland playas during
winter when cover is scarce. Large playas with
abundant, shallow open water are more likely
to be used by geese and cranes, as well as
pintails and wigeons; many ducks such as
mallard and green-winged teal are more
attracted to smaller playas with dense emer-
gent vegetation. There is some use of playa
lakes as sport fisheries.


There are losses and gains among various
playa lake and wetland wildlife communities
of the Southern Great Plains as a result of
agriculture and other human activities.
Adverse impacts linked with crop production

focus on reduced habitat diversity or carry-
ing capacity in playas disturbed by the
cultivation of crops and burning of weeds;
basin modifications to store irrigation tail-
water, which reduces the highly productive
littoral zone and concentrates waterfowl
during dry periods, increasing the disease
potential; and the application of chemicals
for mosquito and weed control, increasing
the potential for wildlife toxicity. Offsetting
benefits include the availability of waste
grain from irrigated row crops as a wildlife
food source; increased density and diversity
of wildlife cover from reception of irri-
gation tailwater in undisturbed playa basins;
and preservation of some aquatic habitat
during drought because of basin modifications
to concentrate stored natural runoff and

Impacts from livestock production stem
from overgrazing of playas and potential
pollution from feedlot runoff. On the other

hand, managed grazing can benefit wildlife
cover and food supplies, and collected feedlot
runoff can help sustain aquatic habitat.
Although basin modifications to concentrate
water storage may aggravate avian cholera,
other diseases are better controlled where
shallow aquatic area is reduced by excavation
and diking.

On balance, present agricultural prac-
tices, especially the collection of tailwater in
undisturbed playas, may produce more
benefits than liabilities for wildlife in the
Southern Great Plains. However, the pro-
jected trends for curtailment of groundwater
supplies and irrigated crop production indi-
cate greatly reduced tailwater input to playas
and, ultimately, reversion to dry land farming
with adverse effects on wildlife dependent on
a wetland environment. The importation of
irrigation water from outside the region, as
proposed in recent years, could ameliorate
this future impact.

Acknowledgements................................................. i

Executive Summary ................................... .... ................ iii

Table of Contents ........................................................ vii

List of Tables ........................................................... xi

List of Figures................................................... ... ................ xiii

1.1 Definition of the Study Region ..................................... 1
-Playa Lake and Wetland Data Sources ............................... 1
1.2. Importance of Playas to Wildlife ..................................... 4
1.3 Purposes of Habitat Characterization ................................. 4
1.4 Status of Playa Wetlands............................................ 8

2.0 PLAYA REGIONAL GEOGRAPHY .................................... 11
2.1 The Occurrence of Playas ......................................... 11
The Southern Great Plains.................. ..................... 11
2.2 Theories of Playa Basin Origin ........................................ 11
2.3 Regional Climate and Geology ...................................... 14
Geologic Features of the Southern Great Plains ....................... 14
Soil Regions of the Southern Great Plains. ........................... 14
2.4 Landforms, Land Cover, and Land Use............................... 19
Bailey's Ecoregions ............................................ 19
Cowardin's Wetland Classification .................................. 23
Regional Land Use ............................................. 29
2.5 Topography and Geohydrology. ..................................... 29
Regional Geohydrology........................................... 38
2.6 Playa Numbers, Sizes, and Distribution ................................ 38
Playa Water Surface Distribution ................................... 41

3.0 PLAYA BASIN ENVIRONMENT......................................... 45
3.1 Playa Basin Soils .............. .............................. 45
Characteristics of Playa Basin Soils ................................ 45
3.2 Hydrology of Playa Basins........................................... 52
Natural versus Modified Surface Runoff ............................. 52
Playa Water-Holding Capacity ..................................... 55
Interactions With Groundwater and the Ogallala Aquifer ................ 55
3.3 Playa Water Chemistry and Quality................................... 60
Unpolluted Playa Water Quality .................................. 60
Playa Water Contamination ....................................... 61

4.0 ECOLOGY OF PLAYA BASINS........................................... 65
4.1 Habitat Classification and Values ................................... 65
Systems of Classification................... ....................... 65
Playa Values for Wildlife................... ....................... 68
Variability and Diversity of Habitat ................................ 77

4.2 Playa Bird Populations ............................................ 77
Waterfowl at Playa Basins ........................................ 83
Other Birds at Playa Basins ...................................... 83
Importance of Playas to Birds ..................................... 85
Habitat Preferences of Selected Species. ........................... 86
4.3 Other Wildlife Populations and Invertebrates ........................... 90 n
Mammals of Playa Basins.................. ...................... 90 |
Reptiles, Amphibians, and Fishes...... ........................... 90
Invertebrates of Playa Basins ...................................... 92 I
4.4 Wildlife Diseases Associated with Playas ............................ .. 92 I
Factors Contributing to Disease ................................... 92
Effects of Disease on Wildlife ..................................... 94
5.0 PLAYA USES AND MODIFICATIONS........................ ............ 95
5.1 Agricultural Water Supply.......................................... 95
Irrigation Water Storage .......................... ................. 96
Recharge of Aquifer Supplies ..................................... 98
5.2 Crop Cultivation and Grazing ....................................... 98
Grazing of Livestock ........................................... 103
5.3 Hunting and Fishing ............................................. 103
Sport Fishing and Other Uses ..................................... 105
5.4 Waste Treatment and Disposal..................................... 106
Disposal of Feedlot Waste.................. ..................... 106
Petroleum Production Waste ..................................... 108
5.5 Water Supply and Disease Control Modifications ........................ 109
Modifications Designed for Aquifer Recharge ......................... 109 =
Modifications for Disease Control .................................. 115
Multipurpose Playa Modifications .................................. 116
5.6 Status of Playa Modifications ..................................... 117 I
Modification Rates and Trends .................................... 121
Influence of Declining Aquifer Supplies ............... ............. 122

6.0 IMPACTS ON PLAYA WILDLIFE HABITAT .............................. 123
6.1 Impacts Linked With Crop Production ................. ... .......... .. 123
Basin Modifications............. ............................... 123
Chemical Application ................. ....................... 127
6.2 Impacts Linked With Livestock Production............................ 127
Operation of Feedlots ......................................... 128
6.3 Impacts Linked With Petroleum Production ............................ 130
6.4 Benefits from Crop and Livestock Production........................... 131
Reception of Irrigation Tailwater .................................. 131 I
Modifications to Concentrate Water ......... ................ 134
Grazing and Feedlot Operations ................................ 134
6.5 Disease Control Benefits .............. ............................ 134
6.6 Projected Trends for Playa Lakes and Wetlands............... ......... 137
Projected Changes for Wildlife Habitats. ............................ 137

CITED REFERENCES ................................................... 139



I Page
APPENDIX A: Plants of Playas in the Llano Estacado ............................. 147
I APPENDIX B: Birds of Playas in the Llano Estacado ................... .......... 153
APPENDIX C: Mammals of Playas in the Llano Estacado.......................... 159
I APPENDIX D: Amphibians, Reptiles, and Fishes of Playas in the Llano Estacado ....... 161
I APPENDIX E: Invertebrates of Playas in the Llano Estacado ....................... 163




2-1. Playa-related wetland classification ..................... ............ . 24

3-1. Playa soil classifications of the Southern Great Plains ........................ 48

3-2. Distribution of common playa basin soil types .................. .......... 49

3-3. Surface horizon of playa basin soils........................................ 50

3-4. Playa water persistence in the Southern Great Plains......................... 58

3-5. Playa-associated springs in the Texas High Plains. .......................... 61

3-6. Analysis of water from representative playas. ............................ 62

4-1. Playa categories based on water retention and vegetation ..................... 66

4-2. Playa classification based on vegetative cover types .......................... 66

4-3. Playa classification by plant community, water persistence, land use, and
modifications ................................... .................. 66

4-4. Playa classification based on land use, floristic, soil and physical variables ........ 69

4-5. Physiognomic types of playa vegetation ......................... .... 70

4-6. Playa types based on modifications and watershed, soil and vegetative variables.... 71

4-7. Wildlife value of playa wetlands ........................ ............... 78

4-8. Attributes of playas receiving or not receiving irrigation tailwater............... 80

4-9. Vegetative zonation found at larger, unaltered playas ........................ 81

4-10. Bird species associated with playa basins. ..................... ...... . 84

4-11. Texas High Plains puddle duck censuses .................................. 85

4-12. Nest densities of ring-necked pheasants. .................................. 86

4-13. Playa habitat features used by selected bird species .......................... 88

5-1. Playa basins excavated for livestock watering .............................. 96

5-2. Playa basins fenced for livestock grazing .................................. 104

5-3. Analysis of effluent from playa clay and Pleistocene material.................. 108

5-4. Seepage of nitrogen and chloride below a feedyard playa ................... 109

LIST OF TABLES (concluded)
5-5. Irrigated land and playas receiving tailwater ......................... . 119

5-6. Irrigated land and playas having modifications .......................... 119

6-1. Negative impacts to wildlife due to playa crop production .................... 124

6-2. Negative impacts to wildlife caused by playa livestock production .............. 129

6-3. Positive impacts to wildlife due to playa crop and livestock production .......... 132

1-1. Orientation of the study region ................. ........................ 2

1-2. Zones of the study region ............................................ 3

1-3. Aerial photo of an unmodified cropland playa ............................. 5

1-4. Photo of a playa providing natural habitat ................................ 6

1-5. Playas classified good to excellent as wildlife habitat .................. ...... 7

1-6. Photo of irrigation water impoundment and recycling ........................ 8

1-7. Aerial photo of a modified cropland playa ................................ 9

2-1. Average dry playa basin surface density ............... .................. 12

2-2. Average temperatures at Amarillo, Texas ................................ 15

2-3. Average precipitation in the Texas High Plains .......................... 16

2-4. Mean evaporation in the Southern Great Plains ............................ 17

2-5. Stratigraphic section of the Texas High Plains. ............................. 18

2-6. Principal soil orders in the Southern Great Plains ........................... 20

2-7. Soil texture zones of the Llano Estacado ................................ 21

2-8. Natural vegetation of the Southern Great Plains ............................ 22

2-9. Habitats in the Lacustrine system ................. .................... 27

2-10. Habitats in the Palustrine system.................. ..................... 28

2-11. Sample National Wetland Inventory map ................ ................ 30

2-12. Major land uses of the Southern Great Plains ................... .......... 31

2-13. Major oil and gas fields of the Southern Great Plains. ........................ 32

2-14. Corn harvested within the study region.................................. 33

2-15. Sorghum harvested within the study region. ............................. 34

2-16. Wheat harvested within the study region. ................................. 35

2-17. Cotton harvested within the study region ............... ................ 36

LIST OF FIGURES (continued)
2-18. Typical topography of small, deep playas ................................ 37

2-19. Typical topography of large, shallow playas ....... ....................... 39

2-20. Productive aquifers in the Southern Great Plains. ........................... 40

2-21. Decline in Ogallala Aquifer water elevation. ............... ............. 41

2-22. Size and soil texture of Texas High Plains playas. ........................... 42

2-23. Average wet-season playa water surface density ............................ 43

2-24. Average dry-season playa water surface density ............................ 44

3-1. Randall and associated soils within a playa landscape ........................ 46

3-2. Particle sizes of playa soils in the Llano Estacado ........................... 47

3-3. Pattern of playa basins, Randall soil zones, and watersheds ................... 53

3-4. Dry playa basin surface density (by counties) .............................. 54

3-5. Wet-season playa water surface density (by counties) ........................ 56

3-6. Dry-season playa water surface density (by counties) ........................ 57

3-7. Rainfall, evaporation, and water volume of unmodified playas ................. 59

3-8. Dieldrin concentrations in playa lake sediments ............................ 63

4-1. Aerial photo of an agricultural playa with poor wildlife habitat ................ 67

4-2. Wet-season playa open water surface area distribution ....................... 72

4-3. Dry-season playa open water surface area distribution ....................... 73

4-4. Aerial photo demonstrating agricultural and wildlife management conflicts ....... 74

4-5. Aerial photo of a modified cropland playa with excellent wildlife habitat ........ 75

4-6. Photo of a rangeland playa with bird nesting and fish habitats ................. 76

4-7. Photo of emergent vegetation in a modified playa. .......................... 80

4-8. Aerial photo of a playa with concentric vegetative zonation ................... 82

4-9. Photo of a large playa lake preferred by pintails ............................ 87

LIST OF FIGURES (continued)
4-10. Photo of an emergent playa wetland preferred by mallards.................... 87

4-11. Aerial photo of a cropland playa yielding good wildlife values ................. 91

4-12. Aerial photo of an agricultural playa which lends itself to aquaculture ........... 93

5-1. Photo of livestock watering at an unmodified playa ......................... 95

5-2. Photo of a playa basin levee used to direct surface runoff...................... 97

5-3. Photo of a playa basin used for irrigation water storage ...................... 97

5-4. Evapotranspiration and irrigation of winter wheat .......................... 99

5-5. Evapotranspiration and irrigation of cotton ........................... 99

5-6. Evapotranspiration and irrigation of grain sorghum. ..................... .... 99

5-7. Aerial photo of a playa basin radically modified by diking and excavation ........ 100

5-8. Photo of a playa modified for irrigation tailwater recycling ................... 101

5-9. Aerial photo of a playa basin with center-pivot irrigation sprinkling ............. 102

5-10. Photo of a typical fenced and grazed playa wetland ......................... 103

5-11. Photo of a good playa basin hunting site ...................... ......... 105

5-12. Aerial photo of a playa basin modified to impound feedlot runoff .............. 107

5-13. Typical unmodified playa lake area-volume curves with land surface configuration 110

5-14. Typical modified playa lake area-volume curves with land surface configuration ... 111

5-15. Aerial photo of a playa central pit excavation. ........................ ... 112

5-16. Photo of a playa peripheral pit excavation ..................... .. . 113

5-17. Aerial photo of playa drainage ditches with a peripheral pit ................... 114

5-18. Photo of a storm runoff channel into a playa basin.......................... 115

5-19. Playa perimeter runoff diversion terrace and storage pit ...................... 116

5-20. System for recharging the Ogallala Aquifer with playa lake water............... 117

5-21. Playa lake vegetative cover, water depth, and mosquito production ............. 118

LIST OF FIGURES (concluded)
5-22. Percentage of playa basins modified ..................................... 120

5-23. Current Southern Great Plains irrigated and dry land crop distributions .......... 121

5-24. Forecast of Southern Great Plains irrigated and dry land crop distributions ....... 122

6-1. Aerial photo of a plowed playa basin with habitat value destroyed.............. 125

6-2. Aerial photo of a playa modified and reclaimed for crop production ............ 126

6-3. Photo of a playa with impacts from excavating and diking .................... 128

6-4. Photo of a playa lake shoreline with impacts from cattle grazing ............... 130

6-5. Aerial photo of a playa with irrigation tailwater and habitat diversity............ 135

6-6. Photo of spoil banks at a modified playa with improved habitat................. 136


The Southern Great Plains playa wild-
life study region is defined to cover parts of
five states where playa lakes and wetlands are
common features in the landscape. Playas are
certainly important to migratory waterfowl in
the Central Flyway; they are critically impor-
tant to resident wildlife in this dry farmland
region where any moist or aquatic habitat is
exceedingly scarce. The main purpose of
characterizing playa habitat is to portray
current knowledge as a basis for new efforts
at habitat preservation and management of
playas for multiple use, including wildlife


Playa lakes and wetlands in the southern
region of the Great Plains occur predomi-
nately within 43 counties comprising most of
north-central Texas, four counties across the
eastern New Mexico border, the southeastern-
most Colorado county, eight counties of
southwestern Kansas, and four counties of
Oklahoma, including the Panhandle. The
study region overlies the Ogallala Aquifer and
is defined by its characteristic landform (flat
or smooth plains) and natural vegetation
(mostly shortgrass prairie). It should be
observed that the Southern High Plains, also
known as the Llano Estacado, occupies the
southern two-thirds of the Southern Great
Plains, lying south of the Canadian River
Breaks (Figure 1-1). Many previous playa
studies have been confined to the Llano
Estacado, thereby excluding the playa country
in Oklahoma, Kansas, and Colorado.

The distribution of playas by size and
density of playa basins among the 60 counties
of the study region, as well as the sub-regional
characteristics of these basins, closely corre-
sponds with sub-regional distinctions in
geology, topography, soils, hydrology, and
vegetation. For instance, the smaller, deeper
playa basins concentrate where medium-
textured sandy loam soils and nonirrigated
cotton croplands predominate, whereas the

larger, shallower basins are concentrated
where fine-textured silty clay loams and
irrigated corn croplands predominate.

To assist the interpretation and com-
parison of playa habitat characteristics as
related to the differences in playa environ-
ments, the study region was partitioned into
five zones: North Cropland, North Rangeland,
South Rangeland, South Cropland, and the
Irrigated Cropland Zone which overlaps the
middle section of the South Cropland Zone
(Figure 1-2).

Playa Lake and Wetland Data Sources.
It must be pointed out emphatically that
most of the wildlife studies supporting this
habitat characterization have been conducted
in or near Castro County, Texas, at the
middle of the Irrigated Cropland Zone. It is in
this zone that six counties (Castro, Deaf
Smith, Floyd, Hale, Lubbock, and Parmer)
have an abnormally high proportion (>30%)
of playas providing good to excellent wildlife
habitat, particularly because of irrigation
tailwater collected in playas here (Guthery
and Bryant, in press). There is substan-
tial danger in extrapolating these findings to
other zones where they are unwarranted. The
more definitive sources of data available for
this characterization focus on the U.S. Bureau
of Reclamation for water resource informa-
tion and on Texas Tech University, the U.S.
Forest Service, and U.S. Fish and Wildlife
Service for wildlife information.

The unpublished data from the 1982
Playa Inventory by the Engineering and
Research Center of the Bureau of Reclama-
tion (Denver) were released for use in this
study. Based on photointerpretation of
LANDSAT imagery, these data reveal for the
first time the distribution of playa water
surface rather than basin surface. The Bureau's
Southwest Region in Amarillo has also spon-
sored playa wildlife assessments by faculty of
the Department of Range and Wildlife Man-
agement at Texas Tech University (Lubbock),


S ..... I

Study '/ .
Region "

Canadian .. .
River '

South hern

Plains < /E'k.K, g
""' } J} I

Flat. Smooth, or Irregular
Plains (after Hammond)

S/ Ogallala Aquifer

Figure 1-1. Orientation of the study region to the southern region of the Great Plains, the
Southern High Plains (Llano Estacado), and the Ogallala Aquifer (Nelson and Associates, Inc.



i ..
""' ""

Figure 1-2. The playa lake and wetland study region and zones of the Southern Great Plains
(Nelson and Associates, Inc. 1982).

notably Guthery et al. (1981) and Simpson
and Bolen (1981).

The Forest Service, through the Rocky
Mountain Forest and Range Experiment
Station at Texas Tech University, has spon-
sored other recent work providing impor-
tant data for this study, particularly deal-
ing with playa wildlife habitat character-
istics (Guthery, Pates, and Stormer 1982;
Guthery 1980).

The Fish and Wildlife Service contribu-
tions of data are contained primarily in the
characterization study by the Ecological
Services Office in Ft. Worth (Curtis and
Beierman 1980). Ecological Services in Tulsa
provided data from the Six-State High Plains-
Ogallala Aquifer Regional Study (Brabander
1981); so has the U.S. Economic Develop-
ment Administration (Banks, Feeley and
Banning 1981). Important earlier data on
water availability in Texas High Plains playas
(Dvoracek and Black 1973) and on playa use
and modification (Schwiesow 1965) resulted
from work sponsored by the Texas Water
Development Board.


The Southern Great Plains playa lake
and wetland region, next to the Gulf Coast, is
the most important sector of the Central
Flyway for wintering waterfowl. About 90%
of overwintering waterfowl in the Texas
Panhandle inhabit playa basins (Figure 1-3).
In the heart of the playa region-Castro
County, Texas, in the center of the Irrigated
Cropland Zone-20 migratory waterfowl
species occupy playa basins. The habitat
features so valuable to migratory waterfowl
are both natural and artificial. The natural
seasonal flooding and vegetative zonation of
playa basins sustain the necessary open water
and diverse natural cover and food supplies,
while surrounding croplands contribute grain
food and, where irrigated, the additional water
supply from irrigation runoff.

Many playas in the semiarid, intensively
cultivated Southern Great Plains serve as oases
of aquatic or semiaquatic habitat (Figure
1-4). Availability of drinking water and dense
cover in some playa basins attracts a variety
of wildlife other than migratory waterfowl,
including shore and wading birds, upland
game birds, passerines, raptors, mammalian
predators, lagomorphs, rodents, reptiles, and
amphibians. Guthery and Bryant (1982)
partitioned and classified the general value of
wildlife habitat in the Southern Great Plains,
based primarily on the amount and perma-
nence of natural vegetation and standing
water. The average proportion of playas
with good to excellent habitat ranged from
3.3 to 28.6%, with the higher proportions
concentrating in the Irrigated Cropland Zone
(Figure 1-5). Playas classified as good to
excellent would provide overwintering and
nesting cover for ring-necked pheasants,
year-round cover for small mammals and
furbearers, and resting and brooding cover for


One important purpose behind this
characterization of Southern Great Plains
playa habitats is to integrate and synop-
size the substantial new knowledge about
playas with the findings of previous research.
In addition to the recent applied research
sponsored by the U.S. Departments of the
Interior, Agriculture and Commerce, two
major symposia sponsored by the Fish
and Wildlife Service (Barclay and White
1981) 'and Texas Tech University (Reeves
1972) have produced a range of findings
and opinion requiring some synthesis to be
made more accessible and placed in an over-
all perspective. The other purpose of the
characterization is to assemble the knowledge
necessary to guide a better informed approach
to the management of playa wildlife habi-
tats and populations to balance the inter-
ests of wildlife conservationists, hunters,
farmers and ranchers, and some municipal
and industrial interests.

IZZ. -

Figure 1-3. Infrared, low-altitude aerial photograph of an unmodified Southern Great Plains
playa basin, supporting hundreds of ducks and other waterfowl with diverse natural vegetative
cover. Open water is supplemented by runoff of irrigation flows; surrounding grain crops
supplement natural food supplies (Texas Tech University, Department of Range and Wildlife
Management 1981).





Figure 1-4. Example of a Southern Great Plains playa basin providing a natural habitat "oasis"
for wildlife in a semiarid agricultural region that is otherwise habitat-poor, especially lacking
lake and wetland environments (Nelson and Associates, Inc. 1981).
6 -
-. .. ..- .




Figure 1-5. Proportion of playas classified good to excellent as wildlife habitat in 12 geographic
strata of the Southern Great Plains (after Guthery and Bryant 1982).


Playa lakes and wetlands of the Southern
Great Plains have undergone major changes
as a result of human activity, primarily
from irrigated crop production and grazing
of cattle. Regional changes, particularly
from alterations to playa basins made to
expand the irrigation water supply (Figure
1-6), have coincidentally benefited and
harmed a variety of wildlife populations
that depend on the scarce aquatic environ-
ments of this semiarid region. Some localized
playa habitats have been severely degraded
while others have been considerably
enhanced, particularly for waterfowl. Because
the common resident and migratory species
have unique optimum habitat requirements,

some populations have gained and others have
lost habitat values that promote their survival
and welfare.

On balance, wildlife abundance has
apparently increased in the Southern Great
Plains among some of the important game and
non-game species, due in all probability to
increased water, cover and food supplies at
farmland playas, especially those surrounded
by irrigated croplands (Figure 1-7). Current
regional projections, however, portend less
water availability and grain crop production
favorable to wildlife, factors that will reduce
playa habitat carrying capacity and wildlife
abundance in the future unless present
schemes to import water from other regions
are carried out.

_' : f _

-.11, H

n- --. RV... ...

.-- tI D--
-- II I- *j I. :

Figure 1-6. Impoundment and recycling of surface runoff into playa basins from irrigated
croplands and cattle feedlots have considerably augmented the irrigation water supply and
reduced pumping costs (as compared to pumping from deep wells), while also promoting open
water and vegetative cover for wildlife (Nelson and Associates, Inc. 1981).


Figure 1-7. Modified playa, having a pit excavated on the basin perimeter, receives irrigation
runoff from surrounding croplands, resulting in greater wildlife habitat diversity and carrying
capacity that is characteristic of a persistent, emergent, palustrine wetland (Texas Tech Univer-
sity, Department of Range and Wildlife Management 1981).



Playa basins occur in many arid or
semiarid regions of the world. In the United
States they concentrate in the Southern Great
Plains as either ephemeral or permanent
lakes or wetlands. The semiarid regional
climate ranges from dry steppe to warm
temperate, and the main geologic feature is
the underlying Ogallala Aquifer. The domi-
nant landform is smooth plains; natural land
cover is mostly shortgrass prairie and the basic
land use is agricultural, with irrigated farm-
lands clustered near the center of the study
region. The flat topography is generally
devoid of stream drainage; playas collect
runoff and evaporate rapidly. The geo-
hydrology involves the comparative isolation
of subsurface aquifers because of imperme-
able clay in playa bottoms. Playas number
about 25,000 within the 68,500-mi2
(177,400-km2) region, occasionally ranging in
size up to several hundred acres (over 100
hectares); the majority are under 10ac
(4ha). Their size distribution is uneven,
with larger playas concentrating near the
center of the region.


Playas are the flat central portions of
arid basins that drain internally, periodically
flood, and accumulate sediment (Neal 1975).
These shallow, plate-like depressions occur in
desert and semiarid regions of the world such
as the Sahara, southern Iran, western
Australia, the U.S.S.R., and the Southern
Great Plains of the United States, as well as in
Utah, Nevada, Oregon, California, and
Arizona. As many as 50,000 playas a few
square kilometers in size occur throughout
the world (Neal 1975).

Playas are referred to by many names,
including salar in Spanish-speaking regions,
sabkha in north Africa, and pans or salt pans
in south Africa and Australia. In English-
speaking regions, they are termed dried lakes,
an obvious misnomer for dry lake beds;playa
lakes which are flooded playa basins (Neal

1975); and salt playas. The term "playa"
itself comes from the Spanish for "shore" or
"beach." The variety of terms given to playas
illustrates that they have various distinguish-
ing features.

Playas generally can be divided into
two main types: ephemeral and permanent.
In a wet condition, the playa basins are
either lakes having little to no vegetation, or
wetlands with aquatic vegetation. Both per-
sistent and intermittent lakes and wetlands
occur within the Southern Great Plains.

The Southern Great Plains. Playa wet-
lands in the U.S. are associated primarily with
the region known as the Southern Great
Plains, which encompasses high tablelands in
southeastern Colorado, southwestern Kansas,
the Oklahoma Panhandle, eastern New
Mexico, and north-central Texas, including
the Texas Panhandle. The region defined for
the study of wildlife associated with Southern
Great Plains playa lakes and wetlands covers
60 counties-one in Colorado, eight in Kansas,
four in Oklahoma, four in New Mexico, and
43 in Texas. The approximate average acreage
of dry playa basin surface per square mile (or
ha/km2) within the five zones of the study
region depicts the surface density of playas
(Figure 2-1).


There are seven theories to explain the
origin of playas, including the development of
karst topography, land subsidence, the
isolation of early pluvial lakes and river
courses, soil slumpage, wind deflation, the
occurrence of buffalo wallows, and meteor
impact. There is some evidence that all of
these processes occurred on the Southern
Great Plains.

The development of karst topography, in
which sinkholes appear in the dissolving
limestone caprock, is not extensive in the
Southern Great Plains, but some sinkholes




Zone --- /



South "*.
Z Zone
(HA/KM )

S0-50- (0.8)

TEXAS 5-10 (0.8-1.6)
N E 10-20 (1.6-3.1)

-------No data

Figure 2-1. Average dry playa basin surface density, by zones of the study region (adapted from
Schwiesow 1965, Dvoracek and Black 1973, and Guthery et al. 1981).



occur in Armstrong, Briscoe, Glasscock, and
Lipscomb Counties, Texas. South of Big
Springs in Howard County, sinkholes in
cretaceous limestone may indicate some karst
development (Reeves 1966).

Land subsidence, in which overlying
sediments compact to conform with the
topography of underlying strata also is a
theory for playa formation (Rettman 1981;
Reeves 1966). There is some evidence of
playa basin development by this process in
Armstrong, Briscoe, and Lipscomb Counties,
Texas, according to Reeves. Because the
Ogallala Aquifer was deposited in hills and
valleys, deposits of thicker sediments filling
the valleys could correspond with areas
where subsidence would cause playa

The isolation of early Pleistocene
pluvial lakes and streams was caused by
reduction of precipitation and runoff and an
associated increase in evaporation rate when
the Southern Great Plains developed into a
semiarid region. The presently flat topog-
raphy covers drainage courses existing during
wetter pluvial periods. Most of these early
stream valleys and depressions were filled
with Eolian and fluviatile debris, but some
depressions remain as playa basins. Large
depressions occur only where the Ogallala
formation is less than 100 ft (30 m) thick,
suggesting that in areas of greater thick-
ness the pluvial streams did not cut deep
enough to create lasting basins (Reeves 1966).
Playas developed by this process such as
Lubbock Lake (Lubbock County, Texas),
which formed 'about 13,000 years ago,
have a generally linear shape. Some west
Texas lakes lie along paleodrainage, including
pre-Ogallala drainage courses that still channel
runoff after storms or are evident in sub-
surface channels.

Soil slumpage, in which salt or other
soluble materials (other than limestone) are
dissolved, causing sinks, is fairly rare in
the Southern Great Plains, although it may
have had some role in the formation of saline

lakes. Sinks in which sodium sulfate
has been dissolved in underlying strata
have been found in Rich and Brownfield
playas in Terry County, Texas (Reeves

The most credible theory of playa
development, and one which describes the
formation of the most circular or oval Great
Plains playas, concerns the process of wind
deflation or blowouts. The formation of
clay dunes or lunettes near playas is highly
suggestive of this process (Price 1972). In
semiarid regions such as the Southern
Great Plains, other factors besides flat
terrain and high and constant winds con-
tribute to the potential for wind erosion.
When clayey sediments dry, a thin crust
forms and breaks into polygonal cakes
(Price 1972; Neal 1965). Price observed
that evaporated salts such as chlorides will
crystallize, causing the crust to break into
fine dust particles easily transported by
wind. The presence in the Southern Great
Plains of "oriented" lakes-basins arranged
in parallel patterns with their axes
aligned-further supports the wind deflation
theory. Oriented lakes characteristically
occur in semiarid regions having bimodal
wind patterns where the average directions
are nearly opposite (Price 1972). This
phenomenon tends to elongate basins from
round to oval.

Playas often have been called
buffalo wallows, but it is doubtful that
buffalo played much part in playa forma-
tion. Playas have always attracted wildlife,
either for cover, water, or salt, and, although
buffalo can carry a substantial amount of soil
in their fur (Rettman 1981), it is unlikely that
they could do more than deepen existing

There are several basins near Odessa,
Texas, which were caused by a meteor
impact, but most Great Plains playas lack
the characteristics of a meteor crater, such as
angular fragments of rock on the rim and
fragments of a meteor.


The climate of this region is classified
generally as mid-latitude semiarid (Critchfield
1966). Although northern and western
portions fit this classification, the climate can
range from dry steppe in the southern district
to warm temperate in eastern sections (Curtis
and Beierman 1980).

Winter temperatures range significantly
from north to south in the study region.
Record summer highs have reached 109-1120
F (43-440C); extreme winter lows have ranged
from -80F (-220C) in the south to -180F
(-280C) in the north (Gale Research Co.
1980). In Amarillo, near the center of the
study region (Potter. County, Texas), normal
daily highs exceed 900F (320C) in July, and
normal daily lows are in the low 20's (-50C) in
January (Figure 2-2). The freeze-free period
normally ranges between 180 and 210 days
from northwest to southeast through the
study region.

The mean annual precipitation gen-
erally decreases from northeast to southwest
in the study region; the low level is about
15 in (38 cm) in the south (Dawson County,
Texas) and the high is about 21 in (53 cm) in
Gray County, Texas (Figure 2-3). On the
average, more than an inch (3 cm) of rain falls
each month between April and October; May
and June are the wettest months with 2-4 in
(5-10cm) (Dvoracek and Black 1973).

The winds in the Southern Great Plains
generally blow from southwest to northeast
with a more pronounced southerly-to-
northerly flow in the summer. Wind speeds
can range between 40 and 60 mph (64-97
kph) for as long as a day in March, April, and
May (Traweek 1981); the highest average
wind speed (7 mph or 11 kph) occurs in the

Evaporation rates are high in the
semiarid climate of the Great Plains. The
mean annual Class A pan evaporation is about

96 in (244 cm) near Amarillo (Potter County)
and 112 in (284 cm) at the southern limit of
the study region (Figure 2-4). The highest
evaporation rates occur in midsummer with
low precipitation and high winds.

Geologic Features of the Southern Great
Plains. About 250 million years ago during
the Permian Period of the late
Paleozoic Era, the Southern Great Plains
was submerged under a shallow inland sea.
During the early Mesozoic Era, the High
Plains region was lifted above sea level;
Permian rocks were eroded and deposited as
the Triassic Red Beds-impervious layers
underlying the Ogallala formation. In the
Cretaceous Period of the late Mesozoic Era,
shallow seas again covered parts of the High
Plains; shales and limestones of the Trinity
and Fredricksburg groups were deposited in
shallow waters (Figure 2-5). Some of these
formations are evident along the south and
southeastern edges of the study region.

In the late Tertiary Period, during the
Pliocene Epoch some 10 million years ago,
uplift of the Rocky Mountains region caused
streams to cut deep canyons through the
Cretaceous rocks. These were deposited as
alluvial fans with thick layers of wet gravel on
the eastern edge of the Rockies. The gravel
deposits trapped much of the stream runoff,
which is now the Ogallala Aquifer underlying
most of the study region (Figure 2-5). During
the Pleistocene Epoch in the Quaternary
Period, the climate turned from wet to dry
and windblown sand and Aeolian sediments
covered the Ogallala; these sediments became
the soils of the Southern Great Plains. Dunes
of this sand are present along river valleys in
the northeastern part of the study region.
During the Quaternary Period, the Southern
Great Plains became elevated smooth plains
with the flow of surface water diverted
southward in the Pecos and eastward in the
Canadian River drainage.

Soil Regions of the Southern Great
Plains. Soils of the Southern Great Plains are
represented by three orders: alfisols-














'- -.

Daily Low

Jan Apr Jul Oct

Figure 2-2. Average temperatures at Amarillo, Texas, in the Southern Great Plains (U.S. Geo-
logical Survey 1970).









(36 cm)

Figure 2-3. Distribution of average annual precipitation on the Texas High Plains (Dvoracek and
Black 1973).





Figure 2-4. Mean annual pan evaporation in the Southern Great Plains region (U.S. Geological
Survey 1970).

64 in
(163 cm)

U K 2 Approximate
0a 0 Formation Description Thickness (ft) (m)

SS Valley alluvium. Stabilized and active
dunes. Black, brown, and white salifer- na.
a T ous played silts.
Tahoks Clay and sand, gray. Bentonitic and 35(11)
Clay and sand, gray and bentonitic.
I Tule Thin-bedded, ripple-marked, freshwater 100 (30)
. S limestone.
SSand and clay, light gray. Bentonitic
Blanco clays. Some freshwater limestone and 70 (21)
; I Clay and sand, reddish-brown. Coarse
-t | a3 Bridwel channel graves. "Cap-odc" at top. 155 (47
Couch Sand, pinkish-gray. Well sorted, thick 125 (38)
basal gravel.
. ... _--,_ _. _----J-UNCONFORMITY E E.....---- -
Shale, yellow-brown to dark gray. Brown
Duck Creek limestone and sandstone. Desmoceras 0-40 (0-12)
abundant at base.
Shale, dark gray to yellow-brown. Thin
Kiamichi gray to yellow-brown limestone and 108 (33)
sandstone lentils. Lower part

Limestone, white to yellow-brown. Thick
Edward$ to massive-bedded. 2030 (6-9)

S a C Limestone, light gray. Thick to massive-
Su Comanche Pk bedded, and argillaceous. Mar interbeds. 50 (15-24)

Shale, light gray. Sandy, light gray.
Walnut Argillaceous limestone abundant. 8-23 (2.5-7)

SSand, light gray to purple. Lenticular 10-5 (3-8)
S Paluxy quartz gravel beds.

Figure 2-5. Stratigraphic section of the Texas High Plains (after Reeves 1966).


non-calcic brown, gray-brown, or gray wood-
land soils; mollisols-chestnut and reddish
prairie soils; and aridisols-reddish-brown and
red desert soils (Buol, Hole and McCracken
1973) (Figure 2-6). Aridisols have clay
horizons but limited profile development, low
organic matter, and high levels of exchange-
able bases. In the Southern Great Plains,
they are usually dry in all horizons, and never
moist as long as 90 consecutive days when
temperatures are suitable for plant growth.
Mollisols have well-developed horizons with
nearly black, organic-rich surface layers and
medium to high base supply. Mollisols of the
region are dry more than 90 cumulative days
in the year. Alfisols often have well-
developed profiles with subsurface horizons
of clay accumulation, moderate organic
material, and medium to high base supply.
Regional alfisols are dry more than 90 cumu-
lative days when temperatures are suitable for
plant growth.

The Llano Estacado of the Southern
Great Plains (Texas-New Mexico High Plains)
has been subdivided into three broad zones of
soil surface texture representing fine,
medium, and coarse soils (Figure 2-7). Other,
less extensive soil texture types occur within
these broad zones. Allen et al. (1972)
reported that surface soils in the "fine" zone
were clay loams and silty clay loams, typically
of the Pullman soil series. Soils of the
"medium" zone, representative of the
Amarillo soil series, consist primarily of fine
sandy loams, with sandy clay loams and loams
quite common in occurrence. The "coarse"
soil zone is dominated by loamy fine sands
and fine sands of the Arvana or Douro soil


The topography- of the Southern
High Plains is fairly uniform. Hammond used
two main classes to distinguish between land
surface forms in this region: Plains and
Tablelands. There are two subclasses of
Plains: Smooth Plains and Irregular Plains.

The Smooth Plains in the study region have
more than 80% gently sloping surface, and 50
to 75% of their surface is upland terrain;
the Irregular Plains are less gently sloping and
predominantly lowland terrain. Most of the
region would be classed as Smooth Plains.

The Tablelands in the study area
belong to one subclass having moderate relief
and 50 to 80% gently sloping surface. The
slope of the Tablelands running east-west
along the Canadian River Breaks is 50 to
75% on uplands, but in Borden, Crosby,
Garza, and Howard Counties, Texas, at the
southeastern edge of the study region, the
same slope is predominantly on lowlands.
The Tablelands generally are bounded by
valley escarpments.

Bailey's Ecoregions. The Southern
Great Plains can be described among three of
Bailey's Ecoregions, which differentiate areas
having similar climate and types of vegeta-
tion classified in a hierarchical scheme with
four main levels. The top level is domain,
which can be defined as a subcontinental
region with similar climate (Cowardin et al.
1979). The Southern Great Plains are divided
between two domains-Dry and Humid
Temperate. The second classification level is
the division which further describes climate
regionally. The Humid Temperate Domain in
the Southern Great Plains has only one
division-Prairie, as does the Dry Domain-
Steppe. The third level of Bailey's classifi-
cation scheme is the province, which describes
broad vegetational classes. The Steppe Divi-
sion encompasses only one province in the
study region-Great Plains Shortgrass Prairie,
while the Prairie Division contains the Prairie
Brushland and Tall Grass Provinces.

The fourth level in Bailey's classification
is the section, which describes dominant or
climax vegetation and coincides closely with
Kuchler's (1964) potential vegetation types
(Figure 2-8). The Prairie Brushland Province
primarily has a grama-buffalo grass associ-
ation, which can be found along the eastern
edge of the study region. Because of


.4.. ....... I. .


Mollisols (organic-rich
& 'it '; -, , ,- .^ .. .'; surface horizon)
S ', .'Alfisols (moderate organic
J,', vY .- ... -. : ; ..'... -. '.". '. '.. : matter; clay horizons)
0Aridisols (dry, organic-poor:

SEntisols (without
pedogenic horizons)

horizons; parent material)
""'" '"" ""' :'^.. t .-': |-? ....Vertisols (cracked clay
,,,". .-; ..',., :. "

Figure 2-6. Distribution of principal soil orders in the Southern Great Plains (U.S. Geological
Survey 1970).

/ I
5.z".:' t ";!,. .
i "" '" "- :
.% :, -' I.
... ( -] As ( or.ga.ni

....... .'.. ..... ... .. ...

Suve 17 0).

! I

- Fine-Textured Soils

F -] Medium-Textured Soils
S] Coarse-Textured Soils

Figure 2-7. Soil texture zones of the Llano Estacado or Southern High Plains (Harris et al.




4 44 o A, .V o .. o4 o 4 a 4 o o o a o .. I
,, 4 4 4 9 4 ^ 40 L /p 4 P4 4 -:
S"7. '' V a. '.'4 "

0 Aoo oo
4 .

44964 1 4 P C NT AL-EATERN

4 4 64 4.4 GN
4 4 4, 4 4. 7997
44&" 4 0 b. Vl A To

4 A VA J a V SL & 4 a
Z- 4 4 e
4 4 49 4 4 44 4 4 4 94 q

4. 4
9..... ".'.a ".4 CC44;. l

C-1 4 4 N-0l4r-ra0, For UsB
4494 a 9 D 4 99 4

.ra Pan :;o4 I -947)

Jll0 .o; ||l| 4 F 44 6
Jill t4 4 4Gay
4 4 A 99 4 4
lill'll. j I p b
44 V. V 4 4 9 4
o ? 0 4 4 4 1 9 : 3
4 94 9 4 4 4 4 4 44 4 .

44 b 0 GRA4SL4 414 44ST
4 .44 : 4 4 4 4 .74 .q : V
q : G ra ssl a n d / F o r e st 4 4 4

llI 4 4 44 4 4 C4 49

'4 o 6 9__ Broadleaf Forest

%.............. Needleleaf Forest

Needleleaf-Broadleaf Forests
Qb a I

overgrazing, the brush species of mesquite has
invaded the area, causing a weed problem for
ranchers (Gould 1968).

The Tall Grass Prairie Province has
a post-climax community dominated by big
bluestem and the associated midgrass-blue
grama. The bluestem-grama association is
present only in Donley, Gray, and Hemphill
Counties, Texas, near the central eastern
edge of the study region; and in Gray,
Haskell, Meade and Seward Counties, Kansas.
There are few stands left of these grasses
because most land has been cultivated. The
soils here are usually fertile mollisols (Bra-
bander 1981). According to Kuchler (1964),
the Great Plains Shortgrass Prairie Province
has grama-buffalo grass as the dominant
vegetation. It is prevalent west of the
bluestem-grama association, being more
adapted to the drier conditions in the main
portion of the study region (Figure 2-8).

Kuchler's classification scheme recog-
nizes three additional classes of vegetation:
juniper-pinyon woodlands, present in Baca
County, Colorado, and Cimarron County,
Texas, in the northwest corner of the study
region; sandsage-bluestem prairie, present in
Morton, Seward, and Stevens Counties,
Kansas; and shinnery oak, present along the
Canadian River Breaks. Shinnery oak habitat
includes clumps of low-growing oaks inter-
spersed with big bluestem.

Cowardin's Wetland Classification. The
playa basins of the Southern Great Plains are
considered wetlands according to Cowardin's
Classification of Wetlands and Deepwater
Habitats (Table 2-1). They have two attri-
butes of wetlands: at least intermittently the
land supports aquatic plants (hydrophytes);
and the substratum is predominantly un-
drained hydric soil (Cowardin et al. 1979).

Cowardin's system for classifying wet-
lands is hierarchical; the highest level is the
system. Of five defined systems, playas fit
into two: Lacustrine (lakes) and Palustrine

(marsh, swamp, bog, fen, or wet prairie).
The subsystem is the next level: Lacustrine
has two subsystems-Limnetic and Littoral;
Palustrine has none. The class is the next level
of the hierarchy and identifies substrate
material, water regime, or vegetative type;
the subclass further defines these iden-
tifiers. Dominance type is a level subordinate
to subclass and describes dominant plant or
animal species. There are also special modi-
fiers, including water regime modifiers,
water chemistry modifiers, and others which
describe animal or human modifications to
the wetland.

Some of the larger playas of the
Southern Great Plains fit into the Lacustrine
System (Figure 2-9). Only those over 20 ac
(8 ha), and probably many of those identified
by name on maps, would fall into the
Limnetic Subclass; most Lacustrine playas
would conform to the Littoral Subclass. The
great majority of playas belong to the
Palustrine System (Figure 2-10), as they lack
the depth and extent of open water neces-
sary to be classed as Lacustrine.

The Fish and Wildlife Service National
Wetland Inventory (NWI) uses a sequence of
letters and numbers (alpha numerics) to iden-
tify each wetland on an NWI map (U.S. FWS,
undated). The first letter in the sequence
represents the system; subsequent digits (up
to five) represent the subsystem, class, sub-
class, and special modifiers (Table 2-1). Some
wetland inventories lack subclass and special
modifier designations since mapping has been
accomplished at various levels of detail based
on regional needs and capabilities.

The following is an example illustrating
how the NWI classification system should
work to describe a large playa with more than
20 ac (8 ha) of open water, at least a 2-m
depth, and a dike on one side:
L 1UB3Gh
(L) System: Lacustrine
(1) Subsystem: Limnetic
(UB) Class: Unconsolidated Bottom

Table 2-1. Playa-related wetland classification according to Cowardin et al. (1979).
Classification Level Code Attributes

Lacustrine System (L) Situated in a topographic depression.
Lacks persistent vegetation on more than
30% of surface area.
Total area is 20 ac (8 ha) or more, or at least
2 m deep with wave-formed or bedrock
Ocean-derived salinity is less than 0.5%.

Limnetic Subsystem (1) All deepwater habitats within Lacustrine
(Lacustrine System) below a depth of 2 m.

Littoral Subsystem (2) All wetland habitat within Lacustrine from
(Lacustrine System) shoreline to a depth of 2 m.
Palustrine System (P) All non-tidal wetlands dominated by
Areas that lack vegetation but which are all
of the following: less than 20 ac (8 ha);
lack wave-formed or bedrock shoreline;
water depth is less than 2 m; ocean-derived
salinity is less than 0.5%.

Unconsolidated Bottom Class (UB) Unconsolidated substrates with at least
25% cover of particles smaller than stones.
Vegetative cover is less than 30%.
Sand Subclass (2) Unconsolidated particles smaller than
stones are predominantly sand; finer and
coarser sediments may be intermixed.

Mud Subclass (3) Unconsolidated particles smaller than
stones are predominantly silt and clay;
coarser or organic material may be
Unconsolidated Shore Class (US) Unconsolidated substrates with less than
75% of the surface area composed of
stones, boulders, or bedrock.
Less than 30% cover of vegetation other
than pioneering plants.
Any of the following water regimes: irregu-
larly exposed, regularly flooded, irregularly
flooded, seasonally flooded, temporarily
flooded, intermittently flooded, saturated,
or artificially flooded.

Table 2-1. (continued)

Classification Level Code Attributes

Sand Subclass (2) Same as for UB Class.

Mud Subclass (3) Same as for UB Class.

Emergent Wetland Class (EM) Wetland characterized by erect, rooted,
herbaceous hydrophytes, excluding mosses
and lichens.
Dominated by perennials.
Vegetation is present for most of growing
season most years.
All freshwater regimes included.

Persistent Subclass (1) Wetland dominated by species that nor-
mally remain standing until at least begin-
ning of next growing season.
Only in Palustrine System.
Non-persistent Subclass (2) Wetland dominated by plants which fall to
substrate or below water surface at end of
growing season, so that in certain seasons
there is no sign of emergent vegetation.

Scrub-shrub Wetland Class (SS) Wetland dominated by woody vegetation
(Palustrine System only) less than 6 m tall.
Includes true shrubs, young trees, or stunted
shrubs and trees.
All freshwater regimes included.

Broad-leaved Deciduous Subclass (1) Dominated by deciduous and broad-leaved
shrubs and trees.
Needle-leaved Deciduous Subclass (2) Dominated by deciduous and needle-leaved
shrubs and trees.
Temporarily Flooded Water Regime (A) Surface waters present for brief periods in
growing season.
Water table well below surface most of
Both upland and lowland plants grow here.
Saturated Water Regime (B) Substrate is saturated to surface for ex-
tended periods of growing season.
Surface water seldom present.

Table 2-1. .(continued)

Classification Level Code Attributes
Seasonally Flooded Water Regime (C) Surface water present for extended periods,
especially in early growing season; absent by
end of season most years.
Water table often near surface when sur-
face water is absent.

Semi-permanently Flooded Water (F) Surface water persists throughout growing
Regime season most years.
When surface water absent, water table at
or near land surfaces.

Intermittently Exposed Water (G) Surface water present throughout the year
Regime all years except during extreme drought.
Permanently Flooded Water Regime (H) Water covers surface throughout year all
Vegetation is composed of obligate

intermittently Flooded Water Regime (J) Substrate usually exposed, but surface
water occurs occasionally without seasonal
Plant communities change as moisture
regime changes.
May not be a wetland if there is a lack of
hydric soils or hydrophytes.

Artificially Flooded Water Regime (K) Amount and duration of flooding con-
trolled by man with pumps or siphons.
Rice-soybean agricultural lands and wildlife
management areas are examples; not irri-
gated pastureland.

Modifier for partially drained/ditched (d) Water level has been artificially lowered by
ditching, but soil moisture is sufficient to
support hydrophytes.

Modifier for farmed (f) Soil surface has been cultivated for farming
Hydrophytes will become reestablished if
farming discontinued.

Modifier for diked/impounded (h) Dike obstructs inflow of water.
Impoundment obstructs outflow of water.

Modifier for excavated (x) Basin was excavated by man.

Table 2-1. (concluded)

Classification Level Code Attributes

Modifier for hypersaline (7) >40 ppt (salinity) >60,000 bMhos (250C)
Modifier for eusaline (8) 30.0 40.0 ppt 45,000 60,000 pMhos
Modifier for mixosaline (9) 0.5 30.0 ppt 800 45,000 pMhos
Modifier for fresh (0) <0.5 ppt <800 pMhos

Modifier for acid (a) pH <5.5
Modifier for circumneutral (t) pH 5.5 7.4
Modifier for alkaline (I) pH >7.4



wZ 0 Z
< .J w < (a
e0 w w z

oo PF -FT o FI ^ F
0 < 0 < 0
0 0O A
wz 0 Q CD 2Z

----------------e- ------- ------- eLP O___________


Figure 2-9. Distinguishing features and examples of habitats in the Lacustrine system (Cowardin
et al. 1979).



z z
-j i J" 0 1-
I.- 1 0 1- -
LU Wj I Mg LU zg z 5 I

a J-L---....B I WAT-'-"U


Figure 2-10. Distinguishing features and examples of habitats in the Palustrine system I
(Cowardin et al. 1979).







(3) Subclass: Mud (silt-clay)
(G) Water Regime: Intermittently Exposed
(h) Special Modifier: Diked/impounded.
A sample portion of an actual 1:24,000-scale
NWI map (Figure 2-11) does not use all of
the digits in Cowardin's system since this
detailed level of classification was not
required regionally. This playa appears to be
modified as the open water is concentrated in
a pit at one side.

Regional Land Use. Land use in the
rural Southern Great Plains is essentially
limited to cropland, irrigated cropland, and
grazing land (Figure 2-12), as well as oil and
gas production (Figure 2-13). Generally,
the area north of the Canadian River Breaks is
used mostly as cropland, except that grazing
is more common to the west in Baca County,
Colorado; Cimarron County, Oklahoma; and
Dallam County, Texas. The area adjacent to
the Canadian River is semiarid grazing land.

South of the Canadian River, the entire
central portion is mostly cropland, with an
interior central portion that is mostly irri-
gated. In Castro, Crosby, Deaf Smith, Floyd,
Hale, Lamb, Lubbock, Parmer, and Swisher
Counties in Texas, and in Curry County, New
Mexico, croplands are irrigated extensively.
The remaining areas in the study region
to the south and west are mostly semiarid
grazing land, except that Roosevelt County,
New Mexico, has a large area used both for
grazing and cropping.

Generally, the oil fields (Figure 2-13)
are in the southern one-third of the study
region where grazing and nonirrigated crop-
lands predominate. There is a concentration
of oil fields in Andrews and Midland Counties,
Texas, and Lea County, New Mexico. Gas
fields are concentrated mostly in the northern
one-third of the study region, primarily where
dry farming is practiced.

The distribution of crops in the study
region is significant in evaluating wildlife
habitat values (Figures 2-14 through 2-17).
Corn, a heavy water user, is mainly

concentrated in two Kansas counties-Gray
and Haskell-and in five Texas counties-
Castro, Deaf Smith, Hale, Lamb, and Parmer-
where there is heavy irrigation (Figure 2-14).
Only 22 out of 60 counties in the study
region have more than 10,000 ac (4,050 ha)
planted in corn. Grain sorghum (Figure 2-15)
is cultivated more extensively than corn in the
Southern Great Plains. Forty-four counties of
60 have more than 10,000 ac (4,050 ha)
planted in sorghum, concentrating more in
the northern dry farming district.

There is a pronounced increase in the
acreage of wheat planted from south to north
(Figure 2-16), concentrating north of the
Canadian River Breaks. Forty-four of the
60 counties are planted in more than 10,000ac
(4,050 ha), and 29 of these have more than
50,000 ac (20,250 ha) planted. Cotton has
almost the opposite distribution of wheat
(Figure 2-17); the major concentration of
cotton farms is in the more temperate
southern half of the study region.


The topography of playas is related to
soil texture. Playas are common in the three
soil texture zones-coarse, medium," and
fine-of the Llano Estacado or Southern High
Plains (Figure 2-7), but they change in shape,
size, and frequency according to soil texture.
In general, the medium-texture zone has a
high density of small, deep, round playas, and
the fine-texture zone tends to have larger,
shallower, and fewer playas (Allen et al. 1972;
Lotspeich et al. 1971). However, data from
Guthery and Bryant (In press) indicate that
playas generally decrease in size north of the
Canadian River Breaks and into Kansas, even
though soils may be finer-textured.

The playa topography in an area of
Lubbock County, Texas, illustrates the high
density of small playas where sandier soils
predominate (Figure 2-18). An area of
Randall County, Texas, illustrates the larger,
shallower playas of the fine-textured



.Compreor Sta Well

St i. f / /r P n PO
PEM: E e n Class

/ ,T [aiypFo w ; / looded
I I \ n o d 34 1 -V -d

S I i I I

EM: Emergent Class
POW: Open Water Class

A: Temporarily Flooded

Figure 2-11. Portion of a sample National Wetland Inventory map showing a large playa near
Amarillo, Texas, with alphanumeric classification (National Wetland Inventory, U.S. Fish and

Wildlife Service).

SMostly Croplands

Forest/Woodlands Grazed and Ungrazed

Subhumid Grasslands/
Semiarid Grazing Lands

7 T Desert Shrublands Grazed and Ungrazed

Figure 2-12. Major land uses in the region of the Southern Great Plains (U.S. Geological Survey


-. -IIi,

Gas Fields

Oil Fields

Figure 2-13. Distribution of major oil and gas fields in the region of the Southern Great Plains
(U.S. Geological Survey 1970).



j /"/ / _-// /// / I OKLAHOMA


South --- -


0-999 (0-404)

S1,000-9,999 (4054,048)
TEXAS' 10,000-49,999 (4,049-20,242)

50,000 + (20,243 +)

Figure 2-14. Acreage of corn harvested by counties within the study region (U.S. Department
of Commerce 1978).




South '*-. .

TEXAS 0-999 (0404)

1,000-9,999 (405-4,048)

m 10,000-49,999 (4,049-20,242)

50,000 + (20,243 +)

Figure 2-15. Acreage of sorghum harvested, by counties within the study region (U.S. Depart-
ment of Commerce 1978).


- Zone



South10,0004999 (4,0492042)


A A North
M TON STE NS WAR M A 0 Cropland
.. ... . -. -----.-. -----.-.-.---*--------

C1 A R T E A B A E

Rangeland /A



0nelan V I9Ir Cropland


7. TEXAS 1,000-9,999 (405-4.048)

*3.i" ^ 10,000-49.999 (4,049-20,242)

50,000 + (20,243 +)

No data

Figure 2-17. Acreage of cotton harvested, by counties within the study region (U.S. Depart- I
ment of Commerce 1978).

Contour interval of 10 ft (3 m)

Scale of 1:62,500

Figure 2-18. Typical topography of small, deep playas where medium-textured sandy loam soils
predominate in the area south of Lubbock, Texas, in Lubbock County (Dvoracek 1981).


"hardlands" where silty clay loam is common
(Figure 2-19). A common "hardland" playa
may have a depth of 2 m and cover close to
150 ac (60 ha), as opposed to a medium-
textured sandy loam playa about 2.5 m
deep, but covering less than 40 ac (15 ha).

Some playa basins in the Southern
Great Plains are larger and deeper than the
majority; they are called "salt lakes" and are
most common in Andrews, Gaines, Hockley,
Lamb, and Terry Counties, Texas, in the
south-central part of the study region, which
has coarse soils. The salt playas usually are
quite large, having up to several square miles
(8 km2) in surface area. They often receive
water from "Ogallala seeps" or springs besides
from precipitation. When the water table is
low, these basins dry out, and a white salt
crust forms on the surface (Allen et al. 1972).

Regional Geohydrology. The Ogallala
Aquifer was laid down as Pliocene sediments
of wet gravel between 125 and 155 ft (38-
47 m) thick. The Ogallala formation is a vast
source of prehistoric water which extends
from South Dakota through Nebraska,
western Kansas, and the panhandle of Okla-
homa into the Texas High Plains (Figure 1-1).
It has served as a spur to development of the
Southern Great Plains by providing its
primary source of water, particularly for
irrigation. Withdrawals from wells in the
study region (Figure 2-20), primarily in the
Irrigated Cropland Zone, have exceeded
5,500 mgd or 6.2 x 106 ac-ft (7.6 x 109 mi3)
annually. Natural recharge of the Ogallala is
only one-tenth to one-eighth of the with-
drawals (Dvoracek and Black 1973), and the
elevation of groundwater is steadily declining
(Figure 2-21) (Templer 1978). Essentially, the
Ogallala is hydrologicallyy isolated"
(Dvoracek and Black 1973), and the utiliza-
tion of this resource is a "mining operation"
(Templer 1978).

Some natural recharge of the Ogallala
Aquifer occurs through seepage from playa
basins, depending on the soil type. Most water
loss from playas is through evaporation, but

studies conducted by Clyma and reported in
Hauser (1968) indicated that the reduction in
playa water volumes often exceeded the
expected evaporation losses. The differences
between the two quantities were determined
to be the seepage losses. Clyma found that
playa seepage in a fine-textured "hardland"
(silty clay loam) soil was about 14% of the
water impounded. Cronin (1961) reported a
seepage rate of about 35% in a clay loam soil,
while Reddell and Rayner (1962) indicated
rates over50% in a sandy loam soil. Apparently
the higher rates occur only when playas are
full, as water flooding the banks then overlies
the more permeable sandy zone beyond the
fairly impermeable clay substrate of the playa
floor (Hauser 1968).


Estimates of the numbers of playas in
the Southern Great Plains usually have been
made from U.S. Geological Survey topo-
graphic or Soil Conservation Service soil
survey maps, and are actually estimates of
playa basins that may contain water either
permanently or seasonally. These estimates
vary and have been as high as 37,000
(Schwiesow 1965), which is apparently an
overestimate. Curtis and Beierman (1980)
counted a total of 24,600 basins, with 20,000
in Texas; 2,000 in Kansas; 1,700 in New
Mexico; 700 in Oklahoma; and 200 in Colo-
rado. Guthery and Bryant (1982) counted
25,390 playas in 54 counties of the Southern
Great Plains. A reasonable approximation
would appear to be 25,000.

From Guthery et al. (1981), it is
apparent that the numbers of playa basins
change considerably among the zones of
the study region. Most of the playa basins
are clustered within the South Cropland
Zone, and are particularly concentrated in
the irrigated district (Irrigated Cropland
Zone), which is central to the South Crop-
land Zone. Conversely, the area around the
Canadian- River Breaks (North Rangeland
Zone) has comparatively few playas. The


Figure 2-19. Typical topography of large, shallow playas where fine-textured silty clay loam
soils predominate in the area south of Amarillo, Texas, in Randall County (Dvoracek 1981).

concentrations within the North Cropland
and South Rangeland Zones are intermedi-
ate between those within the North Range-
land (low) and South Cropland (high) Zones.

The sizes of playa basins, as well as the
numbers, change according to zones within
the study region. The smallest basins are
found in the medium-texture soil region
where the largest playas do not exceed 150
surface acres or 60 hectares (Dvoracek and

Black 1973). In the fine-texture soil region
(South and North Cropland Zones), some
basins exceed 600 ac (240 ha). Generally, the
medium- to coarse-texture soil districts
(primarily South Rangeland) have a greater
number of smaller playas; the fine-texture
districts (particularly South Cropland) have
fewer and larger playas, although Guthery and
Bryant (In press) found a decrease in playa
size north of the Canadian River Breaks into
Kansas (North Cropland Zone). On the whole,


Alluvial Stream Valleys


S... 1 Sandstone/Carbonate Rock

.. Sandstone Rock

Carbonate Rock

81,000 ac-ft/yr
(100 x 101 m'/yr)

Figure 2-20. Productive aquifers and withdrawals from wells in the region of the Southern
Great Plains (U.S. Geological Survey 1970).

70 .

I 80

o 90
c (27.5)



120 I
120 J I I I I I I I I I I I I I I I I I I I
| i i i i i i -- I -- I I -- I I I-- I-- 11 -
(36.6) 195719581959196019611962196319641965196619671968196919701971197219731974197519761977

Figure 2-21. Hydrograph of an observation well on the Texas High Plains (Hale County), illus-
trating the gradual decline in Ogallala Aquifer water elevation (Templer 1978).

as playa sizes increase, total numbers decrease
as does the proportion with medium-texture
soils (Figure 2-22).

The overall surface density of playa
basins varies by study region zones (Figure
2-1). The greatest mean density is 19 ac/mi2
(30 ha/km2) in the Irrigated Cropland Zone.
The mean surface densities for the South
and North Cropland Zones are 9.5 and
6.4 ac/mi2 (1.5 and 1.0 ha/km2), respec-
tively. The North and South Rangeland Zones
have the lowest mean surface densities-3.0
and 2.9 ac/mi2 (0.5 ha/mi2), respectively.

Playa Water Surface Distribution. The
preceding discussion on playa basin distribu-
tion in mean surface density does not account
for the differences in playa water surface
among the zones of the study region. The
following discussion compares the approxi-
mate mean water surface in each zone for
both a wet and dry season. The data were
gathered by LANDSAT imagery and
processed by the Remote Sensing and Engi-
neering Physics Section of the Bureau of
Reclamation's Engineering and Research
Center (Denver Federal Center) in conjunction

with the Bureau's Playa Inventory. Most of
the wet-season LAN DSATscenes were recorded
during September and October 1974; most
dry-season scenes are dated in April of 1978.

There are greater wet-season differences
in mean surface water density between north
and south than between the Rangeland and
Cropland Zones (Figure 2-23). Both North
Rangeland and North Cropland Zones have a
mean water surface per square mile of less
than half an acre (0.2 ha/km2) during the wet
season. This is a rather minimal amount of
water to support wildlife restricted to aquatic
habitat, especially in a wet season. At the
other extreme, the Irrigated Cropland Zone
has a wet-season mean water surface density
of 2.2 ac/mi2 (0.9 ha/km2); greater availa-
bility of playa water surface in this district
reflects the supply of irrigation tailwater,
which more than offsets lower precipitation
than to the north. The South Cropland Zone
has a mean water surface density of 1.5
ac/mi2 (0.6 ha/km2); the South Rangeland
figure is 0.9 ac/mi2 (0.4 ha/kmin2), which may
suggest that, although the basins in this zone
are relatively small, they may afford greater
water availability than previously realized.

Fine-Textured Soils in North Cropland and Rangeland Zones
Fine-Textured Soils in Upper South Cropland Zone

Medium-Textured Soils in Lower South Cropland Zone



(0-2.0) (2.0-4.0)
Area of Lakebed Soils (ac) (ha)

10.0-14.9 15.0-19.9
(4.0-6.1) (6.1-8.1)

30.0-39.9 40.0-49.9 50.0 +
(12.1-16.2) (16.2-20.2) (20.2 +)

Figure 2-22. Numbers of playa basins by size classes and soil texture areas
Plains (after Grubb, Parks and Sciple 1968).

of the Texas High

The dry season data, although having
incomplete coverage of the north and south
limits of the study region, indicate that the
main water availability in playas remains in
the Irrigated Cropland Zone, but it is ex-
tremely low (Figure 2-24). The mean water
surface density in this zone during a dry
season is 0.1 to 0.2 ac/mi2 (0.04-0.08 ha/km2 );
the surrounding South Cropland Zone has a

density between 0.05

and 0.1 ac/mi2

(0.02-0.04 ha/km2). Both the northern and
southern parts of the study region can be-
come extremely dry-less than 0.05 ac/mi2
(0.02 ha/km2) of water surface. Generally, in
a dry season, most playas dry up and only a
very minimal amount of water remains in the
South Cropland and Irrigated Cropland

0-0.5 (0-0.2)
TEXAS 0.5-1 (0.2-0.4)

1-2 (0.4-0.8)

2-4 (0.8-1.6)

W No data

Figure 2-23. Average wet season playa water surface density, by zones of the study region (U.S.
Bureau of Reclamation Playa Inventory 1982).



i I
'-BA -A :-. North
SooN STEVE"NS E EADE Cropland 3
-*-... .. ..---------- ---ne ----------

North .. .
Rangeland T
Zone o M


South -0 ..0
>Cropland I

j ^ M m; U S 1 ...T EX A S 0 .1-0.0 5 (0 4-.0 2 ) I

No Irrigatedata

Figure 2-24. Average dry season playa water surface density, by zones of the study region (U.S.
Bureau of Reclamation Playa Inventory 1982). I




Surface soils of playa basins are gen-
erally clays that form a highly impermeable
seal and increase their water-holding capacity.
Soil texture and percolation vary within the
playa region; fine-textured soils near the
center of the region provide maximum water
retention. The hydrology of playas involves
rapid accumulation of natural runoff during
late spring, gradually subsiding by evaporation
and seepage through the summer except
where basins have been excavated to concen-
trate water. Annual precipitation and runoff
can vary in the extreme. Playa water chemis-
try and quality in unmodified freshwater
playas is generally uniform and highly suitable
for wildlife as well as irrigation purposes.
Some contamination from agricultural chemi-
cals, cattle feedlot runoff, sewage effluents,
and waste oil and brine has occurred.


Playa basin soils are predominately
clay and strikingly similar regardless of
location within the Southern Great Plains,
reflecting similar formative processes. These
soils may be- associated with one of several
soil series with only subtle differences ex-
hibited within the textures of the soil
separates. Economic, historical and wildlife
values are represented in these playa basin

Playa basins are typically defined
as clayey-soil-surfaced depressions, inter-
spersed among the lighter-textured regional
soils. The playa soils are of the Vertisol order
and may be listed as Randall, Lipan, or Ness
clays, Stegall silty clay loams, Lofton clay
loams, or may be uncharacterized with only
the associated upland soils classified (Guthery
et al. 1981; Curtis and Beierman 1980; Buol,
Hole and McCracken 1973). The Randall soil
series is the most frequently observed (Figure
3-1). The various playa and associated soil
classifications from the five zones of the
Southern Great Plains study region have been
synopsized (Table 3-1). Also, the distribu-

tion of common playa basin soil types within
the five-state region has been estimated (Table

Characteristics of Playa Basin Soils.
Soils of playa basins are clearly distinguish-
able compared to surrounding upland soils
because of their contrasting darker color
(Reed 1930). Compared to the more perme-
able soils occupying slopes and surrounding
land, playa bottoms have a very slowly
permeable clay and are poorly drained,
resulting in a high water-holding capacity and
periodic inundation (Bruns 1974). The
surface horizon of various playa basin soils
has been characterized (Table 3-3). These soils
tend to reflect the textural and mineralogi-
cal influence of the associated upland soils in
the silt/sand ratio, but bear little relation to
the upland soil clay fraction (Allen et al.
1972). Playa silts are predominately quartz,
have a considerable amount of feldspar, and
lesser amounts of both potash and plagio-
clase. The clay component of playa basin soils
usually exceeds 50%. The most common clay
mineral is montmorillonite, although con-
siderable illite and lesser quantities of
kaolinite may be present.

Playa surface soils are generally neutral
and have low organic carbon and salt concen-
trations. The underlying strata of playa basins
are highly variable from playa to playa,
ranging from heavy clays to fine sandy loams
having marked dissimilarities in mineralogic
and chemical properties. The particle size
distributions of playa soils sampled from the
three broad soil textural regions of the Llano
Estacado (Southern High Plains) have been
depicted (Figure 3-2).

The Randall and other playa clays are
formed from alternate wetting and drying in
the reworked sediments of the surrounding
Aeolian (wind-deposited) mantle (Bruns
1974), clearly defining the area of hydric
(water) influence (Guthery et al. 1981). Playa
subsoils exhibit marked evidence of mixing,



Eolian OIto
Mantle Soils


Aquifer Estucado
Sodls l

I "




Figure 3-1. Generalized representation of Randall and associated soils within a playa landscape
(Bruns 1974).



1 (0.3

2 (0.6)

3 (10.9

114 (.2

5 (1.5)

" 6 (1.8

7 12.1

8 12A)

9 (2.7

10 (3.0

11 O3A4

12 (3.7

13 (4.0

14 14.3

0 50 100% 0 50 100% 0 50 100,




Figure 3-2. Particle size distribution of playa basin soils in three soil texture zones of the
Llano Estacado (Southern High Plains): (A) Randall 1, (B) Randall 2, and (C) Lipan soils
from the Pullman, Amarillo, and Arvana soil series, respectively (Allen et al. 1972).

Fine-Textured (A)

Coarse-Textured (C)

Table 3-1. Playa and associated soil classifications of the Southern Great Plains, by zones of the study region (various sources).

Dominant Associated Upland Playa Soil Series/
Zone County, State Soil Order Soil Series Miscellaneous Data Reference
North Rangeland Baca, Colorado Aridisol Argids Baca, Nunn No soil designation; classed Woodyard et al. 1973
as intermittent lake.
Quay, New Mexico Aridisol Argids Church Unclassified (saline) Ross and Johnson 1959
Dallam, Texas Alfisol Ustalfs Conlen, Gruver Church adjacent to saline Ford and Fox 1975
playas; Ness on playa
Oldham, Texas Mollisol Ustolls Pullman Randall Pringle et al. 1980
North Cropland Stevens, Kansas Alfisol Ustolls Richfield, Dalhart Lofton Dickey, Eeds and Hecht
Texas, Oklahoma Mollisol Ustolls Richfield Randall Meinders et al. 1958
co Hansford, Texas Mollisol Ustolls Pullman, Zita, Randall Welker et al. 1960
Lipscomb, Texas Mollisol Ustolls Pullman, Estacado, Randall Williams 1975
Irrigated Cropland Curry, New Mexico Mollisol Ustolls Pullman, Mansker, Lofton and unclassified Buchanan and Ross 1958
Castro, Texas Mollisol Ustolls Pullman, Olton, Randall Bruns 1974
Lipan, Estacado
South Rangeland Lea, New Mexico Mollisol Ustolls Kimborough, Drake, Cottonwood, Arch, Turner et al. 1974
Stegall Reeves (commonly saline)
Gaines, Texas Alfisol Ustalfs Kimborough, Arch and Drake bordering Dittemore et al. 1965
Arvana, Amarillo saline playas; Randall in
playa bottoms.

M -OEM -M -m MM

Table 3-1. (concluded)
Dominant Associated Upland Playa Soil Series/
Zone County, State Soil Order Soil Series Miscellaneous Data Reference

Glasscock, Texas Entisol Orthents Reagan, Conger Lipan Dixon 1977
South Cropland Cochran, Texas Alfisol Ustalfs Amarillo Randall Newman et al. 1964

Lynn, Texas Alfisol Ustalfs Church, Lubbock, Randall (often saline) Mowery and McKee
Zita 1959

Table 3-2. Distribution of common playa basin soil types in 31 counties of the Southern Great
Plains study area of Curtis and Beierman (1980).
Randall Clay Lipan Clay Ness Clay Lofton Clay Loam Other or Unclassified
No. % No. % No. % No. % No. %

Colorado 0 0 0 0 0 0 0 0 4 100

Kansas 6 60 0 0 0 0 3 30 1 10

New Mexico 0 0 0 0 0 0 2 9 21 91

Oklahoma 16 100 0 0 0 0 0 0 0 0

Texas-North 11 65 0 0 6 35 0 0 0 0

Texas-Mid 28 80 0 0 0 0 0 0 7 20

Texas-South 0 9 10 91 0 0 1 9 0 0

Study Area 61 53 10 9 6 5 6 5 33 28


Table 3-3. Description of the surface horizon of various playa basin soils (various sources).
Soil Characteristics
Playa Soil
(County) Texture Color Structure Consistency pH Boundary Reference
Lofton Clay Loam Dark brown Granular Hard (dry); n.a. Clear Dickey, Eeds, and
(Stevens, friable (moist) Hecht 1961
Stegall Silty Clay Loam Grayish brown to Very fine, sub- Slightly hard, Non- Abrupt Turner et al. 1974
(Lea, NM) very dark brown angular blocky friable (moist); alkaline
sticky and
plastic (wet)
Randall Silty Clay Very dark gray Moderate, very Very hard and Neutral Clear, Williams 1975
(Lipscomb, fine, subangular firm (dry) wavy
TX) blocky
o Randall Clay Very dark gray Moderate, fine Very hard, firm Neutral Diffuse Bruns 1974
(Castro, TX) blocky (dry); sticky, and smooth
and plastic (wet)
Randall Clay Very dark gray Moderate, fine Hard (dry); firm Weakly Gradual Dittemore et al.
(Gaines, TX) to medium, (moist); very alkaline 1965
irregular sticky (wet)
Randall Clay Very dark gray Moderate, medium, Extremely hard Moderately Gradual, Pringle et al. 1980
(Oldham, subangular very firm (dry) alkaline smooth
TX) blocky and fine
Randall Clay Dark gray Moderate, fine Very hard (dry); Weakly Diffuse Newman et al. 1959
(Lamb, TX) blocky and very firm alkaline
irregular blocky (moist); very
sticky and
plastic (wet)

mm m m m --.m m m mm mm-m mm l

- ~ -- F

Table 3-3. (concluded)
Soil Characteristics
Playa Soil
(County) Texture Color Structure Consistency pH Boundary Reference
Randall Clay Dark gray Coarse, granular Very hard Neutral Gradual Murphy et al. 1956
(Cimarron, to blocky (dry) to alkaline
Randall Clay Dark gray to dark Blocky Very hard (dry) Neutral Gradual Meinders et al. 1958
(Texas, OK) grayish brown
Randall Clay Dark grayish brown Massive Very hard (dry); Weakly acid Abrupt Mowery and McKee
(Lynn, TX) firm (moist); (6.8) transition 1959
very sticky (wet)
Randall Clay Dark brown to very Compact Sticky (wet) Weakly Abrupt Newman et al. 1964
(Cochran, dark gray (browner alkaline to transition
TX) in sandier soils) neutral
Ness Clay Gray to very dark Strong, coarse Extremely hard, Mildly Smooth Ford and Fox 1975
(Dallam, gray blocky very firm (dry) alkaline
Lipan Clay Gray to dark gray Moderate, fine Very hard (dry); Moderately Gradual, Dixon 1977
(Glasscock, and medium blocky very firm alkaline smooth
TX) (moist); very
sticky and
plastic (wet)
Note: Baca County, Colorado, playa soil zones are designated "intermittent lakes," and soils are not characterized.

indicating slumping of surface soils into the
deep, wide cracks that appear in dried basin
soil (Allen et al. 1972). Surface features of
most playas are influenced by the rate of
capillary discharge that produces "puffy"
ground (expanded pore space and decreased
density), as well as the frequency of surface
water flooding that removes the surface
accumulation due to evaporation, resulting in
smooth, extremely flat, hard ground (Neal
1975; Motts 1969). Guthery, Pates and
Stormer (1982), noting a further relation
between playa soil and water action, reported
that the area of a playa basin watershed was
positively correlated with the area of the
Randall soil zone.

The water retention capacity of playa
soils makes them highly attractive to agricul-
ture for water collection, storage, and reuse.
Various components of the playa sediments
may have economic value, such as clay,
sand, gravel, gypsum, borax, lithium, and
uranium (Reeves 1978). Reeves reported that
in addition to the economic values of playa
sediments, these deposits contain the sedi-
mentary history of the region and possess
paleo-climatic evidence such as fossil remains
of plants and animals.

Resident and migratory wildlife benefit
from the enhanced water retention of playa
basin soils. High water-holding capability,
combined with playa modifications such as
diking and excavations, collect and concen-
trate water, providing a wetland resource in
an otherwise dry land (Simpson and Bolen
1981). The U.S. Soil Conservation Service
recognizes the wildlife value of playas by
assigning a soil suitability rating of "1" (well
suited) for the aquatic and semi-aquatic
habitats that result from water retention by
playa clay.


Playa basin hydrology is influenced by
agricultural practices, including basin modifi-
cation for water collection and retention and
grazing in the watershed. Water reaching the

playa is derived primarily from precipitation
and runoff within the basin watershed.
Water retention times range from temporary
to long-term, depending on regional soil zone
characteristics, local playa soil types, evapo-
transpiration processes, and amounts of
precipitation and runoff. Interactions be-
tween groundwater and playa lakes or wet-
lands are generally restricted to spring flow
into playas.

Natural Versus Modified Surface Run-
off. The playa basin system of the Southern
High Plains (Llano Estacado) functions as the
main regional drainage network; no significant
stream drainage system exists (Figure 3-3).
These basins collect water primarily in two
peak. periods-May and September-as a
result of regional convection storms. Playa
basin water collection typifies the seasonal
and long-term extremes of the region; periods
of flood and drought are likely and occur fre-
quently over time.

The average playa basin surface density
varies considerably from county to county
within the study region (Figure 3-4).
Aronovici, Schneider and Jones (1970)
reported an estimated average runoff into
Southern Great Plains playas ranging from 2
to 3 x 106 ac-ft/yr (2.5-3.7 x 109 m3/yr),
amounts which are equivalent to one-fourth
to one-third of the -water pumped from
the Ogallala Aquifer for irrigation in this
region. However, a subsequent estimate
ranged up to 8 x 106 ac-ft (9.9 x 109 m3)
during a wet year (Palacios 1981). The
accumulations of runoff vary with the
amounts of precipitation, watershed size and
condition, soil characteristics, degree of slope,
rates of infiltration and evaporation, land use,
and conservation practices (Dvoracek and
Black 1973). Direct rainfall into the playa
basin is a significant factor accounting for
large volumes of water accumulation, accord-
ing to Dvoracek and Black.

Runoff into playa basins is in-
fluenced by the surrounding soil texture;
greater volumes of runoff are recorded on

Figure 3-3. Pattern of playa basins with internal Randall soil zones and surrounding water-
sheds for an area in Lubbock County, Texas (Bowden 1967).




/ c North
S/ ORT SE Cropland
-- Zone


North .".
Zone- AL A M N S Lip OM


/R Y

South '-.....


R (HA/KM2)
A 0-5 (0-0.8)
Ao N -J5.10 (0.8-1.6)
/ r TEXAS 10-20 (1.6-3.1)

S-. m^ 20-40 (3.1-6.2)
MIOLAND 40 + (6.2 +)
No data

Figure 3-4. Average dry playa basin surface density, by counties within the study region I
(adapted from Schwiesow 1965, Dvoracek and Black 1973, and Guthery et al. 1981).


fine-textured soil, with successively lesser
amounts on medium- and coarse-textured
soils. Watershed size and condition affect
the volume of water delivered to the playa
basin. For instance, one-half inch (1.3 cm) of
rainfall in a playa watershed could produce
4 to 5 ac-ft (4,900-6,200 m3) of runoff
during the spring, but no runoff from a
similar storm in late summer, the main
difference being the extent of soil disking and
vegetative cover (Lubbock City-County
Health Unit 1962). Playa watershed slopes
also influence runoff, producing increased
runoff and decreased infiltration as the slope
increases. Moore (1980) states one important
influence of land use on playa water supply;
basins receiving irrigation tailwater sustained a
larger water surface area or volume for a
longer period than those dependent solely on
rainfall. Playas modified to receive irrigation
tailwater collect from 1 to 2 x 106 ac-ft/yr
(1.2-2.5 x 109 m3/yr) or approximately
one-fifth of the irrigation water pumped in
the Texas High Plains (High Plains Under-
ground Water Conservation District No. 1
1977). Most of the water collected in playas is
reused for irrigation or is lost by evaporation
(Jenkins and Hofstra 1970).

Playa Water-Holding Capacity. Taken in
perspective, playa basins are dry most of the
time; the term "playa lake" is used when the
basin surface is covered with water (Motts
1969). Prior to Southern Great Plains agricul-
ture, water retention in the basin was
balanced between precipitation and evapora-
tion. Factors associated with present agricul-
tural practices influence playa water perma-
nence; playa lakes may be either ephemeral or
relatively permanent in water retention as a
result of modification. Wet-and dry-season
average playa water surface density, derived
from recent LANDSAT imagery (1974 and
1978), varies considerably among counties
within the Southern Great Plains study
region (Figures 3-5 and 3-6).

Motts (1969) presented the concept of
flooding ratio, describing the length of time
that water remains in a playa as a means of

differentiating between playas and playa
lakes. The percentage of days per year that a
playa contains open water defines a yearly
flooding ratio. Motts noted, however, that a
10-year flooding ratio may be of more value
as the longer time frame offsets potentially
erratic annual precipitation. A yearly flood-
ing ratio of less than 0.25 (25%) for several
years would classify the basin as a playa;
whereas a basin with a flooding ratio of
greater than 0.75 (75%) would qualify as a
lake. Based on a rather small (0.4%) non-
random sample, Curtis and Beierman (1980)
estimated the persistence of playa water
during 1979 within the five-state study
region (Table 3-4). As compared to 33% of
playas estimated by Curtis and Beierman to
contain water more than nine months of the
year (spring-summer-fall), Guthery et al.
(1981) found that 10% of unmodified playas
contained water in a drouthy summer
(1980), based on a 9% random sample. There
may be little discrepancy here since over
two-thirds of the playas classed as perennial
by Curtis and Beierman had been modified.

Playa water-holding potential varies
with the degree of lake-bottom saturation and
the prevailing evapotranspiration rate. Be-
cause of the lack of outlets, large surface
area, and shallow depths of most unmodified
playas, the bulk (90%) of accumulated water
is lost through evapotranspiration (Aronovici,
Schneider and Jones 1970; Lubbock City-
County Health Unit 1963; Reed 1930).
Grubb and Parks (1968) reported playa
evaporation losses exceeding 0.9 ac-ft of
water per surface acre (450 m3/ha) during a
month; according to unpublished Bureau of
Reclamation data, losses may exceed 2.0
acre-feet per surface acre (1,000 m3/ha) at
times (Guthery et al. 1981). The monthly
distributions of rainfall, evaporation losses,
and average playa water volume in the vicinity
of Lubbock, Texas, have been documented
(Figure 3-7).

Interactions with Groundwater and the
Ogallala Aquifer. Playa basin water infiltra-
tion rates may be rapid initially because of


SA0-0.5 (0-0.08)
S DA SON 0.5-1 (0.08-0.16)

.:-.-TEXAS _"1-2 (0.16-0.31)

4 + (0.62 +)

SNo data

Figure 3-5. Average wet season playa water surface density, by counties within the study region
(U.S. Bureau of Reclamation Playa Inventory 1982).


0-0.05 (0-0.008)

A A 0.05-0.1 (0.008-0.016)
TEXAS 0.1-0.2 (0.016-0.031)
"MA"I"O A.A f'OWS N O.WA'-
0.2-0.4 (0.031-0.062)
._ ;s 0.4 + (0.062 +)

No data

Figure 3-6. Average dry season playa water surface density, by counties within the study region
(U.S. Bureau of Reclamation Playa Inventory 1982).


Table 3-4. Estimated rates of playa water persistence in 31 counties of the Southern Great Plains
study area of Curtis and Beierman (1980).


No. %

0 0


No. %

1 25

Perennial With Pit, Pond
or Ditch in Basin
No. % of Perennial Playas

3 100

2 20 4 40 3

New Mexico





5 22 10 43 8 35 4

2 13 1

9 53

6 13 81 1

3 18 5 29 5

13 37 12 34 10 29 8

3 27

9 7 64 3

Study Area Total

38 33 30 26 48 41 27



No. %

3 75


4 40

' Normally containing water more than nine months of the year.
2 Normally containing water from three to nine months of the year.
3 Normally containing water less than three months of the year.

4 (102)

3 (7.6)


8 (20.3)

6 (15.2)

4 (102)

2 (5.1)


20 (24,675)-

6 16 (19,725)

0 12 (14,800)

8 (9,875)

4 (4,925).



Jan Feb

Jan Fec Mar Apr May


Jun Jul Aug Sep Oct Nov Dec

Figure 3-7. Monthly distribution of rainfall, free-surface evaporation losses, and average water
volume of unmodified playas in the vicinity of Lubbock, Texas (Ward and Huddleston 1972).

dessication cracks, but decrease rapidly as the
clay particles expand with water (Harris et al.
1972). Allen et al. (1972) concluded that
little water percolation or Ogallala Aquifer
recharge occurs through playa soils. Dvoracek
(1981), however, reported that about 10% of
playa water infiltrates to naturally recharge
the aquifer. Templer (1978) observed that
high percolation rates (10-15% of accumu-
lated water) occur only in the southern sandy
loam areas of the Southern High Plains (Llano
Estacado) from the small lake basins of
that region.

Playas are geologically uncommon
in that they concentrate total interior drain-
age of both surface and groundwater. Be-
cause playas often occupy the lowest eleva-
tions of the region, they may interact with
groundwater, which can occur in three
ways: by plant uptake and evapo-
transpiration; by capillary discharge through
the playa surface, originating from aquifers by
artesian movement; and discharge from
springs that occur near junctions of fine-
grained upland soils (Motts 1969). Capillary
discharge depends on groundwater depth
and circulation; water table depths greater
than 5 m produce little discharge, resulting in
dense playa crusts having little accumulation
of evaporative salt deposits (Neal 1975).

Reeves (1970) observed that some of
the playa basins on the Texas High Plains had
flowing springs; most were intermittent with
substantial variation in annual flow. Three
major types of playa springs have been
identified: runoff, Cretaceous, and Ogallala
springs (Table 3-5).


Playa water quality ranges from
superior in freshwater playa lakes to inferior
in saline playas. Pollution of playas may
derive from agricultural, municipal, and indus-
trial sources, with the latter posing more
persistent contamination in a small number
of playas. Water in freshwater playas is

supplied mainly from precipitation and there-
fore is usually of excellent chemical quality.
Playa springs, on the other hand, interact with
mineral deposits, which considerably reduce
basin water quality.

Saline playas, referred to as "salt lakes"
on the Llano Estacado (Southern High
Plains), contrast sharply with freshwater
playas (Allen et al. 1972). The salt playas are
most common in Andrews, Gaines, Hockley,
Lamb, Lynn, and Terry Counties of Texas;
their development apparently has depended
on the presence of exposed Cretaceous
sediments (Rettman 1981; Allen et al. 1972).
Saline playa basins may be several square
miles (7 or 8 km2) in extent, with water
availability more a function of water table
fluctuations than amounts of surface runoff.
These "salt lake" basins reveal a white salt
crust during periods of lowered ground-
water (Allen et al. 1972). High sodium
chloride, calcium sulfate, ferric sulfate, and
other dissolved mineral concentrations of the
saline playas create a different ecosystem
compared to freshwater playas. These high
salt levels limit the production of most
aquatic vegetation and invertebrate species
(Pence 1981).

Unpolluted Playa Water Quality. The
water quality of uncontaminated freshwater
playa lakes tends to be similar throughout the
Southern High Plains (Llano Estacado),
regardless of soil textural zone (Lotspeich,
Hauser and Lehman 1969). Compared with
Ogallala groundwater, playa lakes generally
have lower dissolved solids, but much higher
levels of suspended solids and bacteria (Wells,
Huddleston and Rekers 1970). Frequent
winds in the region and a lack of windbreaks
perpetuate high suspended solids (turbidity)
levels in playa water; this condition in-
creases as the lakes dry. Also, Sublette and
Sublette (1967) attributed higher turbidity
levels of certain playas to poorly vegetated

Other playa water chemistry values are
consistent with good quality irrigation water:

Table 3-5. Major types of playa-associated springs in the Texas High Plains (after Reeves 1970).

Runoff Springs

o Flow mainly after wet periods

o Usually located along base of Eolian dunes on east and northeast sides
of present playas

o Tend to reappear in same location annually, the area frequently be-
coming "quick" when saturated.

Cretaceous Springs

Ogallala Springs

o Flow year-long at steady rate

o Usually located on southwest, west, or northwest sides of present
playas, near or directly above Cretaceous rock outcrops.

o Flow mainly during the period of September to April, apparently in
response to cessation of irrigation

o Usually located away from present playa edge, occurring along drain-
age channels or escarpments on the southwest, west, and northwest
basin sides.

pH ranges from 7.0 to 9.0; nitrates are gen-
erally below 2.0 mg/; and chlorides are
below 10 mg/ (Lehman 1972; Lotspeich,
Hauser and Lehman 1969). Water chemistry
values have been determined from four
playa lakes near Lubbock, Texas (Table 3-6).

Playa Water Contamination. Playa
basins. concentrate runoff water from the
surrounding watershed, ultimately accumu-
lating various soluble compounds that may
have been applied to the adjacent land or
placed directly within the basin. Playas
may sustain increased loads of somewhat
persistent contaminants because these basins
constitute the major drainage system
of the Llano Estacado (Southern High
Plains), and the relatively impermeable
playa clays hold the pollutants within
upper surface layers (Wells, Huddleston and
Rekers 1970; Lubbock City-County Health
Unit 1963).

Typical sources of playa contamination
include agricultural chemicals (fertilizers,
herbicides, and insecticides), runoff from
cattle feedlots, municipal sewage and

stormwater effluents, petroleum development
wastes such as brine, and other industrial or
military discharges. Some degree of contami-
nation from agricultural chemicals can be
expected, depending on the application rates,
chemical persistence, water drainage sources,
and the drainage surface area. Insecticides are
sometimes directly applied to playas for
mosquito control.

Playa water quality studies have
detected fertilizers (nitrate and phosphorous),
herbicides and insecticides in selected playas
at concentrations low enough to designate
these waters safe for consumption by humans
and livestock (Wells, Rekers and Huddle-
ston 1970; Lotspeich, Hauser and Lehman
1969). Sediment samples from playas selected
for wide land use representation were found
to contain aldrin, dieldrin and DDT in con-
centrations generally well below 1 ppm
(Figure 3-8) (Wells, Rekers and Huddleston
1970). No measurable concentrations of
herbicides were reported. Due to the shrink-
swell process and cracking of playa soils,
contaminants can move downward and
surface exposure is reduced.

Table 3-6. Results of complete analysis of water from four representative playa lakes near
Lubbock, Texas, in September and October 1961 (Lubbock City-County Health Unit 1962).
Chemical Parameter Concentrations (ppm)
Lake I Lake II Lake III Lake IV

Calcium 40 34 54 32

Magnesium 9 4 12 12

Iron 0.98 0.55 6.3 2

Manganese 0.05 0.05 0.05 0.05

Sodium 10 3 27 22

Carbonate 0 0 0 0

Bicarbonate 155 124 196 185

Sulphate 26 8 59 12

Chloride 14 2 26 14

Fluoride 1.1 1.2 1.2 1.2

Nitrate 0.4 0.4 0.4 0.4

Dissolved Residue (T.S.) 210 138 355 245

Phenophthalein Alkalinity as CaCO3 0 0 0 0

Total Hardness as CaCO3 155 102 161 152
Specific Conductance (pmhos/cm) 350 230 592 408

pH (units) 7.2 7.9 7.9 7.9

Contamination of playa basins resulting
from collection of feedlot runoff has pro-
duced high ammonia, nitrate and bacterial
levels in local playas, although little ground-
water pollution has resulted because of
impervious clay in the playa bottom (Wells,
Rekers and Huddleston 1970). Petroleum
production wastes (oil, brine, and related
substances) have been reported at several
playas, most prominently from Lake Whalen,
Texas, where hydrocarbon levels ranging from
176 to 481 ppm have been detected (Vogler
1979). Curtis and Beierman (1980) noted that
municipalities, industries and the military
have used some playa basins as holding or
disposal ponds for waste discharge. Although
the pollution is presently confined to only a








few basins in the region, the future potential
for playa contamination may be significant
because of direct exposure and bioavailability.

The quality of spring waters flowing
into Texas High Plains playa basins is gen-
erally poor (Reeves 1970). Of the playa
springs tested for water quality, most ex-
ceeded 500 ppm of total dissolved solids, 1.7
ppm of fluoride, 50 ppm of magnesium, and
250 ppm for both chloride and sulfate.
Passage through saline sediments causes
runoff spring water to deteriorate. Creta-
ceous springs are reported to have uniformly
poor water quality, while Ogallala springs
tend towards marginal quality because of the
surrounding saline sediments (Reeves 1970).

-. .-.- -



0 1 2 3 4 5 6 7 8 9 10 11 12
(0.3) (0.6) (0.9) (1.2) (15) (1.8) (2.1) (2.4) (2.7) (3.0) (3.4) (3.7)

Depth of Sediment (ft) (m)

Figure 3-8. Dieldrin concentrations in sediment layers of two rural playa lakes in Lubbock
County, Texas (Wells, Rekers and Huddleston 1970).


Playa habitat classification following
the National Wetland Classification System
treats all playas as palustrine or lacustrine
wetlands. Habitat values hinge on the collec-
tion of irrigation tailwater, as well as water-
shed size, water surface area and depth, water
persistence, height and density and inter-
spersion of vegetation, and the extent of basin
cultivation, grazing, and excavation to con-
centrate water. Playas may ensure valuable
winter cover for upland birds, and those
containing open water provide valuable
loafing, roosting, watering, and foraging sites
for migratory waterfowl. Playa bird popula-
tions of importance include upland game
birds, raptors, and passerines, in addition to
overwintering waterfowl. Other wildlife popu-
lations of importance include many furbearers
and a few reptiles and amphibians; most fishes
are introduced. Invertebrate production is
important in the playa food chain. Wildlife
diseases associated with playa basins are
encephalitis, avian cholera, botulism, and
duck schistosomiasis.


A variety of habitat classification
systems has been devised to encompass the
diversity of habitats afforded by playas and
other wetlands. When the playa basins collect
natural runoff and irrigation tailwater, a great
biomass of vegetation may be produced,
providing a variety of cover and food for a
diverse community of wildlife. In an agricul-
turally intensive and, for the most part, dry
region, many playas appear as "islands" of
wetland habitat and serve to concentrate

Systems of Classification. Several
systems of ecological classification have been
applied or devised in attempts to differentiate
and characterize playa basins. According to
Cowardin et al. (1979), playas are classified as
palustrine wetlands which have less than 20
surface acres (8.1 ha) of water, less than

2 m of depth at low water, and/or greater
than 30% coverage of emergent vegetation..
Common class and subclass categories are
vegetated or mud flats and persistent or non-
persistent emergent wetlands: Stormer, Bolen
and Simpson (1981) believed that the
Cowardin system could be useful in playa
classification, although it would not provide
adequate definition for localized research and

Simpson and Bolen (1981) suggested a
localized playa classification composed of six
categories based upon water retention, type
of vegetation, and height of vegetation
(Table 4-1). These authors reported that the
physiognomy of cover (height, density, and
other physical characteristics of the vegeta-
tion) is more valuable for classification
purposes than the vegetative species,
especially regarding wildlife values. A playa
with low vegetative diversity and inter-
spersion, encroaching cropland, and an
ephemeral water regime would have relatively
low value as wildlife habitat (Figure 4-1).
Moore (1980) used a simplified playa classifi-
cation based on broad classes of vegetation:
emergent cover; partial emergent cover;
agricultural cover; and rangeland (Table 4-2).

Guthery and Bryant (1982) applied a
playa classification system for a 52-county
area of the Southern Great Plains that in-
cluded plant communities, water persistence,
land use, and playa modifications in the
characterization of playa wildlife habitat
(Table 4-3). Playa habitats were classified as
low value (farmed), low value (grazed),
moderate value, and high value. Guthery and
Bryant regarded the playa habitat value as
species-specific; they noted, however, that
playas classified as moderate to high in value
are relatively more important to wildlife as
they contribute more habitat interspersion
and diversity.

Guthery (1980) and Guthery, Pates
and Stormer (1982) developed a playa


Table 4-1. Six categories of playas based on water retention, type of vegetation, and height of
vegetation (after Simpson and Bolen 1981). I
(1) Agricultural-Ephemeral: Surrounding land totally or predominantly in crop production
with varying degrees of cultivation encroaching on basin borders; water availability is

(2) Agricultural-Permanent: Similar to "Agricultural-Ephemeral," but with some water present
throughout the year. I

(3) Rangeland-Ephemeral-Tall: Mostly rangeland with basins usually fenced; ephemeral water;
tall vegetation. I

(4) Rangeland-Ephemeral-Short: Similar to "Rangeland-Ephemeral-Tall," but vegetation is less
than one meter in height; generally grazed heavily. I

(5) Rangeland-Permanent-Tall: Similar to "Rangeland-Ephemeral-Tall," but with year-round
water retention. I

(6) Rangeland-Permanent-Short: Similar to "Rangeland-Permanent-Tall," but without well
developed marginal communities of tall plants, and lacking the taller grasses. I

Table 4-2. Playa classification based on four vegetative cover types (after Moore 1980).
Category 1: Playa lakes with more than 25% of area covered by emergent vegetation (i.e.,
cattails, bulrush).

Category 2: Playa lakes with less than 25% of area occupied by emergent vegetation. U

Category 3: Agricultural crops planted into or through the playa basin regardless of the per-
centage covered by emergent vegetation. 9

Category 4: Rangeland vegetation is dominant with little or no emergents; generally grazed. U

Table 4-3. Playa classification based on plant communities, water persistence, land use, and playa
modifications (after Guthery and Bryant, in press). 5
(1) Low Habitat Value-Farmed: Area occupied by persistent, natural plant communities is less
than one hectare, with the remainder of the playa disked or cropped, regardless of size. 3

(2) Low Habitat Value-Grazed: Playa area generally lacks plant communities because of heavy
grazing, regardless of size.

(3) Moderate Habitat Value: Playas that provide one to eight hectares of persistent natural
plant communities that are ungrazed or lightly grazed, regardless of modification or
cultivation in other portions of the basin. I

(4) High Habitat Value: Playa area and associated wildlands total eight hectares or more
and support growth of permanent vegetation or permanent open water, regardless of 3
cultivation or modification in other portions of the basin.

.. *

.. w
-* A

A a-

Figure 4-1. Agricultural playa with a mix of mesic disturbed forbs and wheat crops at the
perimeter yields poor wildlife habitat due to low vegetative diversity and interspersion. Entire
basin has been plowed; contour furrows surrounding the basin help to conserve surface runoff
(Texas Tech University, Department of Range and Wildlife Management 1981).


classification system composed of 64 variables
reflecting land use and playa modification,
physical features, soils, and vegetation (Table
4-4). Factor analysis of floristic data collected
from playas in Bailey, Castro and Lamb
Counties of the southwest Texas Panhandle
was used to examine vegetative associations
with typical environmental influences; 14
physiognomic types were identified (Table
4-5). Twenty playa types were isolated
through cluster analysis of these data (Table
4-6). Factors considered most responsible for
clustering of vegetative and physiognomic
variables include moisture regime, soil distur-
bance, and stability of flora. Guthery (1980)
observed that different clusters could result in
different years because of rapid playa changes
resulting from variations in rainfall and basin

The distribution of open water surface
area within playa basins by county and size
class during wet and dry seasons in the 1970's
has been documented (Figures 4-2 and 4-3).
The distribution demonstrates the variability
of playa lakes and wetlands, depending on
overall precipitation and runoff. Also, it
underscores the widespread availability of
open water for- wildlife during a wet season,
and very curtailed but critical availability in a
dry season.

Playa Values for Wildlife. Wetlands
tend to promote greater productivity than
most other naturally occurring ecosystems.
Nutrient exchange is enhanced in playa
wetlands by periodic drying; this process
accelerates plant growth, increasing food and
cover for wildlife (Simpson and Bolen 1981).
Most wetland habitats on the Southern Great
Plains are furnished by playa basins; in wet
years they provide 230,000 to 250,000 sur-
face acres (93,000-101,000 ha) of aquatic
habitat (Curtis and Beierman 1980; Sander-
son 1976). Pence (1981) noted that a
majority of wildlife populations of the
region are associated with playas. The basins
are a natural attraction for terrestrial and
aquatic wildlife, and are responsible for
regional waterfowl abundance, providing

many features essential for their existence
(Bolen and Guthery 1982; Green 1972).

The primary factor determining wildlife
species composition and abundance, habitat
value and use is the greater floral biomass and
tall, persistent vegetative cover afforded
by the wetter soils of playa basins (Curtis and
Beierman 1980; Bolen, Simpson and Stormer
1979). Agricultural practices of the playa
region such as monoculture, weed control,
and clean tillage ensure that cover, except
for crops, is nearly nonexistent; what cover
does exist is confined largely to the playa
basins except in rangeland zones. Conflicts
may occur in agricultural areas where playa
basins providing wildlife habitat when flooded
in wet years are cultivated in drier years with
a loss of habitat (Figure 4-4). Other inter-
actions between farming activities and a playa
basin have substantially increased the wildlife
habitat value (Figure 4-5). Playa vegetation
may offer habitat having high ecotone (edge
effect) and the only suitable vegetative cover,
especially during fall and winter, allowing
resident wildlife to persist and migratory
wildlife to overwinter and breed in the spring
(Guthery 1981a; Simpson and Bolen 1981).
Playa basins have a unique vegetation, differ-
ing substantially in species and frequency of
occurrence from plant communities of the
surrounding prairie. The vegetative cover is
quite variable, depending on the season of
basin flooding and the period of inundation;
plants range from annual and perennial forbs
and grasses to wetland and woody vegeta-
tion associated with riparian woodlands
(Rowell 1981; Curtis and Beierman 1980).
(Appendix A contains a checklist of plant
species associated with playa basins.)

Because of the wide variation in playa
types and vegetation, habitat value varies for
different animal species. Some playas offer a
variety of habitat for both terrestrial and
. aquatic wildlife (Figure 4-6). Guthery and
Bryant (1982) concluded that nearly 13%
of about 25,000 Southern Great Plains playas
had moderate- to high-value wildlife habitat in
August 1980; three-quarters were found in

mmmmmm m-m mm

Table 4-4. Components of a playa classification system based upop land use, floristic, soil and physical variables (after Guthery 1980).
Land Use Variables Floristic Variables Soil and Physical Variables
(1) Type of modification (i.e. physical interfer- Bur sedge Echinodorus sp. (1) Area of watershed
ence with natural basin hydrology) Water clover Marsilea sp.
Arrowhead Sagittaria sp. (2) Type of Randall soil
o Central levee Cattail Typha spp.
o Central pit Spikerush Eleocharis spp. (3) Area occupied by Randall soils within
o Central pit and peripheral levee with ditch Pondweed Potamogeton sp. the watershed
o Central levee with adjacent ditches and Bulrush Scirpus spp.
peripheral ditch Buffalograss Buchloe dactyloides (4) Area occupied by fine sandy loams
o Central levee with one or more ditches Wheatgrass Agropyron smithii within the watershed
leading into it Vine mesquite Panicum obtusum
o Peripheral levee Johnsongrass Sorghum halepense (5) Area occupied by loams within the
o Peripheral levee with peripheral pit Amaranth Amaranthus spp. watershed
o Peripheral pit with one or more ditches Gray ragweed Ambrosia grayii
leading into it Marestail Conyza canadensis (6) Area occupied by clay loams within
o Trench excavation across the Randall soil Helenium Helenium sp. the watershed
zone Annual sunflower Helianthus annus
o Unmodified Curltop smartweed Polygonum (7) Area occupied by all other soil series
lapathifolium within the watershed
(2) Cubic meters of soil excavated for Dock Rumex spp.
modifications Verbena Verbena sp.
(3) Presence or absence of irrigation tailwater Elm Ulmus sp.
recovery within the Randall soil zone Saltcedar Tamarix gallica
(4) Number of irrigation pumps present Barnyardgrass Echinochloa crus-galli
(5) Percentage of basin outside the Randall soil Canarygrass Phalaris carolinensis
zone in contour furrowing Kochia Kochia spp.
(6) Percentage of Randall soil either disked, Devilweed Aster spinosus
plowed, or planted in crops Lambsquarters Chenopodium sp.
(7) Presence or absence of grazing within the Wild lettuce Lactuca sp.
Randall soil zone Blueweed Helianthus ciliaris
Smartweed Polygonum amphibium
Tumbleweed Salsola kali
Cocklebur Xanthium sp.
Willow Salix nigra

Table 4-5. Names, attributes, and prevalence of physiognomic types at playas (n=101) of Bailey, Castro and Lamb Counties, Texas (after
Guthery, Pates, and Stormer 1982).

Height of
Physiognomic Vegetation Playas With
Type (m) Dominant' Taxa (feature) Secondary' Taxa (feature) Each Type (%)
Open water Pondweed (Potamogeton spp.) Arrowhead (Sagittaria longiloba) 28
Broad-leaved 0.5-1.2 Smartweeds (Polygonum bicorne, Barnyardgrass 36
emergent P. lapathifolium) Spikerush (Eleocharis spp.)
Narrow-leaved 1.0-1.5 Cattail (Typha domingensis) 13
emergent Bulrush (Scirpus spp.)
Mesic forb 0.2-1.0 Devilweed (Aster spinosus) Smartweeds 26
Gray ragweed (Ambrosia gray) Barnyardgrass
Wet meadow 0.2-1.0 Barnyardgrass (Echinochloa crusgalli) Smartweeds 41
Red sprangletop Spikerush
(Leptochloa filiformis) Devilweed
Johnsongrass 0.5-1.5 Johnsongrass (Sorghum halepense) 17
Disturbed forb 0.5-1.5 Kochia (Kochia scoparia) Horseweed (Conyza canadensis) 9
Blueweed sunflower (Helianthus ciliaris) Wild lettuce (Lactuca spp.)
Cultivation Variable Crop 20
Mudflat <0.5 Absence of vegetation Barnyardgrass 16
Water-hyssop (Bacopa rotundifolia)
Spoil bank Kochia 17
Camphor-weed (Heterotheca spp.) Tumbleweed (Salsola kali)
Midgrass 0.5 Western wheatgrass (Agropyron smithii) 1
Vine-mesquite (Panicum obtusum)
Shortgrass <0.2 Buffalograss (Buchloe dactyloides) Gray ragweed 13
Road-pit2 Variable Absence of vegetation 12
Tree-shrub Variable Willow (Salix nigra) 21
Saltcedar (Tamarix gallica)
Siberian elm (Ulmuspumila)
'Dominant taxa were those that were most prevalent in terms of coverage; secondary taxa were those that commonly occurred in a type,
but had lower coverage than the dominant taxa.
2The road-pit physiognomic type refers to calcareous spoil (caliche) deposited for road fill or excavated from borrow pits in the basin.

M -M M g mm M M M M M

Table 4-6. Playa types (n=101) based on watershed, soil, and vegetative variables, and playa modifications in Bailey, Castro
and Lamb Counties, Texas (after Guthery 1980).
R Size of
x Randall Randall Extent of Modification or
Playa Number Watershed Soil Zone Zone Modifi- Particular Plant Communities Interspersion Wildlife
Type in Sample Size (ha) Size (ha) fiction (m ) Within Randall Soil Zone Index Value
I 21 3.1 2.2 n.a. Disked for weed control or 1.0 Poor
routinely farmed

II 3 4.0 *4.0 *20,800 31% cultivation; no consis- 3.7 Low
tent community

III 14 33.6 3.2 500 Mostly cultivated; no consistent 1.9 Low

IV 7 18.4 6.7 200 30% of soil zone occupied by 57% 6.0 High
mesic forbs

V 1 27.4 5.5 0 Shortgrass community 1.0 Poor
VI 12 48.2 5.3 400 12% of soil zone in broad-leaved 4.8 Moderate
emergents; remainder in mesic forb
VII 3 45.2 9.8 21,000 All receive irrigation tailwater; wet 5.7 High
meadow community over 33% of
soil zone
VIII 9 62.7 6.1 700 Wet meadow on 55% of playas 4.0 Moderate

occupying 23% of soil zone

IX 5 77.3 10.4 120 Broad-leaved emergent community 2.8 Low
on 60% of playas, occupying 13%
of zone

X 5 94.4 8.1 700 80% receive tailwater; wet meadow 4.4 Moderate
on 48% of soil zone
XI 2 89.5 15.7 14,700 Aquatic and semi-aquatic plant 4.0 Low-Moderate
communities on 70% of soil zone
XII 1 84.8 15.6 *37,500 80% cultivated; open water present 0.9 Low
XIII 4 107.4 14.8 3,200 Receive tailwater; wet meadow 4.0 Moderate
aquatic/semi-aquatic communities
on 77% of soil zone

XIV 2 115.3 9.1 300 Mesic forb community on 71% of 2.5 Low
soil zone

XV 4 122.9 20.2 2,700 Wet meadow, mudflat, and open 6.0 High
water communities on 40%, 13%,
and 4% of soil zone, respectively
XVI 2 134.1 10.1 3,000 Receive tailwater; wet meadow, tall 5.0 High
disturbed forb, and open-water

XVII 1 *150.0 *0.4 0 Entire zone cultivated 0.0 Poor
XVIII 2 154.9 17.5 4,700 Wet meadow and broad-leaved 5.0 High
emergent, aquatic and semi-aquatic
communities on 55% and 80% of
soil zone
XIX 2 177.2 14.7 14,500 Open water, aquatic and semi-aquatic 6.0 High
XX 1 *261.3 *2.4 1,300 Five physiognomic communities 7.0 High
from mesic to hydric with none
exceeding 1 ha
*Distinctive playa attribute





*-.~j-*.- \

Groups of 10 playas each with
less than 10 ac (4.5 ha) of
open water

Groups of 10 playas each with
10-100 ac (4.5-40 ha) of open

Single playas with more than
100 ac (40 ha) of open water

Figure 4-2. Wet-season distribution of playa lakes and wetlands by size classes based on surface
area of open water (U.S. Bureau of Reclamation Playa inventory 1982).




, o /


o o0


o 0 o0 o0
0 1


o0 0
0 0o_
0 .

0 0

0 0
o 000

o 0

- i~g I ~

000 0
0 0
0o o0 0

0 0o

PoO d
00 0


a a. 4

0 00

"0 Oo0 00 0 0 0
CUE ooA o SWSHER o 00

n 0 0 o


_, .0 0o Oo 0

1'YOAKUM E O L Y N 0 0
Zone 0 o0 O 0

M00 IN 0 0 A0

0- 00.-.

ooO 0


M4EADE Cropland



o 0 011

00 0 '6 OKLAHOMA

00 0 *
o0 o0


Single playas with less than
10 ac (4.5 ha) of open water

) Single playas with 10-100 ac
(4.5-40 ha) of open water


0 Single playas with more than
100 ac (40 ha) of open water

No data

Figure 4-3. Dry-season distribution of playa lakes and wetlands by size classes based on surface
area of open water (U.S. Bureau of Reclamation Playa inventory 1982).





Fg mr -A A c t al s .. an
-- ---. -J W.- 4* &k^ .- "
.- s rt c. ,i I. .a c o
of Ran and-Widl i fe. M ane -- .... ,



Figure 4-4. Agricultural playa, showing flooded crops and recovery of broad-leaved emergent as
well as tall- and short-mesic forb communities. Photograph demonstrates the conflict existing
between agricultural and wildlife habitat management goals (Texas Tech University, Department I
of Range and Wildlife Management 1981).
Z ,- = =-= .,, ;I

Figure 4-5. Cropland playa exhibits signs of past basin plowing, but has since been modified to
collect and store irrigation tailwater. Wide variety of vegetation has become established, ranging
from emergent aquatic plants to shrubs and trees having high interspersion, producing excellent
wildlife habitat (Texas Tech University, Department of Range and Wildlife Management 1981).



4 9-; :v

Figure 4-6. Rangeland playa with a border of brush and tree species, habitat that enhances
mourning dove and heron nesting. Playa has sufficient depth to support a catfish population .
(Nelson and Associates, Inc. 1981).

.. .... .
;L.' :.

less than one-fifth of a 52-county study area
(Figure 1-5).

Pates, Guthery and Stormer (1980)
found that tailwater interception by playas
was associated with increased plant species
interspersion and, consequently, increased
the value of wildlife habitat. Larger playa
basins (>4 ha) promote better, more perma-
nent wildlife values, as they tend to be culti-
vated less and have more persistent natural
vegetation. Those basins that are unused and
unmanaged may provide superior cover values
for wildlife (Guthery 1981a). The variability
of playa basins and their wildlife values based
on physiognomic communities has been estab-
lished (Table 4-7).

Variability and Diversity of Habitat.
Playa water levels fluctuate during the year,
depending on rainfall and land use; the
pattern of fluctuations can influence the
utility of playas for wildlife populations.
Wildlife dependent on aquatic habitat tends
to exhibit "boom or bust" fluctuations as a
result of the variability of available water
surface in playas (Bolen and Guthery 1982;
Simpson and Bolen 1981). Freshwater
playas produce a rather complex habitat
used by resident and migratory wildlife for
resting, feeding, and breeding. Use of
saline playas by sandhill cranes is generally
restricted to loafing and roosting; watering is
provided at freshwater springs (Iverson and
Vohs 1981).

The ephemeral nature of most playa
wetlands seldom allows a stable flora. Playa
basins may have a dense cover of annual and
perennial terrestrial, semi-aquatic or aquatic
vegetation, or may be barren, depending
on the timing, intensity and amount of
precipitation and irrigation runoff, the extent
of grazing, and the size of playas. Vegetative
and other attributes of playa basins that do
and do not receive irrigation tailwater have
been compared (Table 4-8). Tailwater recov-
ery is associated with larger playas, greater
coverage by plant communities, and higher
interspersion of plant communities. A playa

basin that has been modified to collect and
store irrigation tailwater is likely to support
emergent vegetation (Figure 4-7).

Playa basins may produce vegetative
zonation (communities) in concentric bands
from the basin center to the perimeter in
response to decreasing water depths or soil
moisture levels. The zonation increases
habitat diversity and typically occurs at larger,
unaltered playas (Guthery 1981b). The
general sequence of vegetative zonation has
been reported (Table 4-9) and illustrated
(Figure 4-8). Such zonation is not typical of
all playa basins; small playas that collect
limited runoff may support prairie vegetation
or may be cultivated. Except for the smart-
weed complex, the shallow, medium-size
basins may be devoid of plant communities
because of cultivation. The playa basins that
are large enough to have an open expanse of
deep water may have aquatic plant commu-
nities (Guthery 1981b).

Playa basin vegetation undergoes sig-
nificant seasonal variation. Winter and early
spring, which are normally dry, are the
periods of greatest vegetative uniformity in
playas (Ward and Huddleston 1972). Juen
(1981) reported that playa vegetation is most
critical for raccoons during these months
when water, food and cover are scarce. Prior
to winter and the first killing frost, playa
vegetation going into dormancy is affected by
rainfall from intense thunderstorms, input of
irrigation tailwater, and the accumulated
water volume in the basin. Gradual evapora-
tion before the frost results in an after-frost
cover of dense, dead vegetation that conserves
soil moisture and protects emerging plants.
Poor vegetative cover and attendant poor
protection against wind erosion result in
playa lake basins that dry out after the first
killing frost (Ward and Huddleston 1972).


The most common wildlife associated
with playa basins is bird life. Simpson and
Bolen (1981) reported pronounced changes

Table 4-7. Wildlife value of playa wetlands (n=101) in Bailey, Castro and Lamb Counties, Texas, based on physiognomic com-
munities (after Guthery 1980).

Number Randall Community Type and Mean
Playa in Soil Zone Playa Extent of Randall Soil Interspersion Playa Wildlife
Type Sample Area (ha) Code Modification (if any) Zone Covered (%) Index Values

A *40 2.73 D, P, Over 95% of Randall zone General absence of physiog- 0.48 Poor
disked; 10% receive nomic communities management
tailwater potential

B 1 2.22 No tailwater *Md. grs. (84%), Jhn. grs. (8%); 6.0
Tr. shb. scattered groves in-
crease interspersion

C 3 2.71 D, P Cult. (48%) 2.0 Poor

D 3 4.43 H Receive tailwater Wt. mdw. (21%) TI. dst. frb. 6.33
(12%), Opn. wtr. (10%); total
of 11 different plant communities

E 1 6.32 H Mdflt. (27%), TI. dst. frb. (22%), 4.0 Suitable feed-
Wt. mdw. (16%), Rd. pt. (4%), ing habitat for
Tr. shb. (3%) shorebirds and

F 1 6.05 P, Massively modified *Spl. bnk. (35%), *Rd. pt. 4.0 Poor
(30%), Cult. (30%) management

G 6 4.53 Msc. frb. (53%), Brd. Ivd. 5.33
emrg., TI. dst. frb., Jhn. grs.,
Tr. shb., Rd. pt., Cult., Mdflt.,
Wt. mdw.

H 3 8.73 Receive tailwater Opn. wtr. (13%), Aqtc./Semi. 6.33
aqtc. (42%), Dst. frb. (13%)

I 4 5.31 D, Altered extensively; Mdflt. (73%) 4.0 Suitable feed-
*disking perpetuates ing habitat for
mudflats shorebirds and

J 3 6.45 Rd. pt., Cult., Wt. mdw. occur 4.33
uniquely on each of the 3

K 3 6.05 H 80% of Randall soil zone Brd. Ivd. emerg. (40%), Cult. 8.33 Wildlife value
cultivated in past 33% low due to ex-
tensive cultiva-
tion; excellent
for ducks if
shallow water
is present

L 6 9.96 D 83% receive tailwater Wt. mdw. (59%), Msc. frb. (9%), 5.7 Excellent feed-
Opn. wtr. (5%), Spl. bnk. (5%), ing habitat for
TI. dst. frb. (4%) ducks if
shallow water
is present

M 4 8.89 D Receive tailwater Msc. frb. (62%), Dst. frb., 7.25
Wt. mdw.

N I 5.51 Occupied by shortgrass n.Q. Quality habitat
community for western
and black-
tailed prairie

Table 4-7. (concluded)
Number Randall Community Type and Mean
Playa in Soil Zone Playa Extent of Randall Soil Interspersion Playa Wildlife
Type Sample Area (ha) Code Modification (if any) Zone Covered (%) Index Values

0 4 11.9 D Receive tailwater; Brd. Ivd. emrg. (41%), 4.75 Excellent feed-
grazing occurs Wt. mdw. (9%), Sh. grs. ing habitat for
(9%) ducks if
shallow water
is present

P 2 18.75 H Receive tailwater Wt. mdw. (40%), Nr. Ivd. 6.0 Excellent due
emrg. (16%), Aqtc./Semi- to large size;
aqtc. (82%) excellent feed-
ing habitat for
ducks if
shallow water
is present

Q 2 13.04 H Msc. frb., Wt. mdw., Nr. Ivd. 7.5
emrg., Cult.; all in equal

R 5 12.05 D Massive irrigation tail- Opn wtr. (63%), brd. Ivd. 7.0 Provide loafing
water results in year- emrg. (15%), Dst. frb. (10%) habitat for
long lake waterfowl

S 2 14.92 Receive tailwater Opn. wtr. (41%), Wt. mdw. 5.5 Provide loafing
(28%), TI. dst. frb. (14%) habitat for

T 1 15.6 P, Massive modification *Cult. (80%) 3.5

U 2 15.73 Mdflt. (74%), Nr. Ivd. emrg n.a. Suitable feed-
(14%) ing habitat for
shorebirds and

V 4 21.19 D Receive tailwater Wt. mdw. (53%), Dst. frb. 5.0 Excellent feed-
(10%), Msc. frb. (8%), Brd. Ivd. ing cover for
emrg. (8%), Sh. brs. (7%) ducks if
shallow water
is present

Playa Code
Distinctive playa attribute
D Distinctive playa type
H High wildlife management potential
P Poor wildlife management potential
Community Abbreviations
Tr shb. Tree shrub
Jhn. grs. Johnsongrass
Md. grs. Midgrass
Sh. grs. Shortgrass
Cult. Cultivation
Mdflt. Mudflat
TI. dst. frb. Tall disturbed forb
Msc. frb. Mesic forb
Brd. Ivd. emrg. Broad-leaved emergent
Nr. Ivd. emrg. Narrow-leaved emergent
Wt. mdw. Wet meadow
Semi. aqtc. Semi-aquatic
Aqtc. Aquatic
Opn. wtr. Open water
Spl. bnk. -Spoil bank
Rd. pt. Road pit

Table 4-8. Comparative attributes of playas that do (n=60) and do not (n=41) receive irrigation
tailwater in Bailey, Castro and Lamb Counties, Texas (Pates, Guthery and Stormer 1980).
Receives Tailwater No Tailwater
Variable x SE x SE
Area (ha)


Randall soil

Broad-leaved emergents

Narrow-leaved emergents



Open water

Mesic forbs

Wet meadow

Disturbed forbs

Community interspersion index

* A,>' (- r^'h -- .-M.

72.4 6.79

9.6 0.73

1.0 0.18

0.3 0.14

0.5 0.17

0.1 0.04

1.1 0.31

1.0 0.23

2.2 0.43

0.4 0.17

5.7 0.27

30.7 5.50

2.7 0.36

0.0 0.00

0.0 0.00

1.3 1.34

0.0 0.00

0.0 0.00

0.0 0.00

0.1 0.10

0.0 0.00

0.3 0.13

Figure 4-7. Emergent vegetation in a playa basin that is modified by excavation and diking to
collect and store irrigation tailwater for subsequent recycling (Nelson and Associates, Inc.

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