Biogeoeconomics of phosphorus in a Florida watershed

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Biogeoeconomics of phosphorus in a Florida watershed
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Thesis (Ph. D.)--University of Florida, 1994.
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Includes bibliographical references (leaves 225-233).
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Typescript.
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Vita.
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Carolyn Fonyo Boggess.

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BIOGEOECONOMICS OF PHOSPHORUS IN A FLORIDA WATERSHED














By

CAROLYN FONYO BOGGESS


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY













ACKNOWLEDGEMENTS

am grateful to have had the opportunity to work with my committee chair, Dr.


Odum.


Through his brilliance and creativity, he has inspired me to view the


world from a systems perspective.


Many thanks go to other members of my committee


for their contributions: Dr. Mark Brown, Dr. Richard Fluck, Dr. Clyde Kiker, and Dr.

Clay Montague.

This work was an outcome of research supported by the South Florida Water


Management District.


I am indebted to all of the team players whom I have worked


with over the years including project leaders Dr. Bill Boggess, Dr. Ken Campbell, Dr.

Richard Fluck, and Dr. Jim Jones; coworkers Hugh Dinkier, Greg Kiker, Dr. Harbans

Lal, and Babak Negahban; and District contract manager Dr. Eric Flaig.

I would like to acknowledge my parents, who lovingly cared for their grandson,


Matthew, in order to provide time for me to complete the dissertation.


Finally, this


research could not have been accomplished without the love and support of my

husband, Bill.














TABLE OF CONTENTS


page


ACKNOWLEDGEMENTS

LIST OF TABLES .


*I a a a


a a S SS a


LIST OF FIGURES


S S S S a a S S a a a a a a S S S S X1 j


EMERGY SYMBOLS AND DEFINITIONS


ABSTRACT


S S S S S Sa a X l


S S S a a a S S S C 5 5 a aa a a S


CHAPTERS


INTRODUCTION


General Concepts


a a S S S 5 4 4 51


a a a a a a a a a 2


Concepts Relating Phosphorus, Emergy, and Economics


Phosphorus as a Resource


* S 5 5


a a p 5 S S S SS 48


Previous Studies of Ecological Economics of Chemical Cycles


Characteristics of the North Okeechobee Basin


History of Basin Development
Related Studies of North Okeechobee Basin
Phosphorus Management Alternatives
Description of Scenarios .


Dissertation Plan


. 1


. . . C 14


S21
S23
* S a S S S 5 25
S29
S.35


METHODS


PROCEDURES


AND SOURCES OF DATA.


S37


Organization of Data with the ARC/Info Geographic Information


System. .
Phosphorus Budgetin
Emergy Evaluation
Economic Analysis
Scenario Comparisor


. p a. . . . 37


a a 44


* S S S


- - 54


* a a a a S a 57
* a a a S 5 S 59







RESULTS


ft t t t t t f 9 ft ft ft ft ft ft ft 4 t t t t f 6 2


Phosphorus Budgeting
Emergy Evaluation
Economic Analysis


*I ft ft 9 ft


* f ft t t t f f 99 4 6


DISCUSSION


Relating the Phosphorus Cycle to Emergy and Economics
Effects of Management on Regional Spatial Characteristics
Comparing Measures of Success for Phosphorus Management .


General Principles of Biogeoeconomics
Suggestions for Future Research


158


APPENDICES


ASSUMPTIONS AND DATA SOURCES FOR PHOSPHORUS


BUDGETING AND ECONOMIC ANALYSIS


PHOSPHORUS MANAGEMENT EMERGY EVALUATION


TABLES.


REFERENCES


BIOGRAPHICAL SK


ft t S9 t ft S t t t t f f f f f ft ft ft ft ft ft2 2 5

:ETI'1-. t S ft... 234.













LIST OF TABLES


Table


page


Drainage Subbasins of the North Okeechobee Basin


S S S S S S 5 1


Land Use


Characteristics of the North Okeechobee Basin


S S S S S S S 5 20


Management Practices for the Base Case Scenario (1993 Conditions)


Dairy Land Uses and Land Use


Tags Assigned to Dairy Polygons


S S S S


Hydrography Attribute Codes and Arc Length Classifications


S S S S 4.5


Phosphorus Assimilation Coefficients and Average Flow Path Lengths


Drainage Subbasin in the North Okeechobee Basin


S S S S S S S S S 5 55


Phosphorus Budget Results by Land Use for the Base Case Scenario


Phosphorus Budget Results by Land Use


. 63


for the Maximum Phosphorus Use


. 64


Scenario


Phosphorus Budget Results by Land Use for the Dispersed Phosphorus


Management Scenario,


Design 1.


Phosphorus Budget Results by Land Use for the Dispersed Phosphorus


Management Scenario,


Design


S . . 66


Phosphorus Imports to and Exports from the North Okeechobee Basin under the


Base Case Scenario


S~~~~ ~ ~ ~ S S S S S S


Phosphorus Budget Results for the Concentrated Phosphorus Management


Scenario


S S S S S S 91


Emergy Evaluation of the Base Case Scenario.


Emergy Evaluation of the Maximum Phosphorus Use Scenario


3(1






Emergy Evaluation of the Predevelopment Scenario


3-10.


Emergy Evaluation of the Dispersed Phosphorus Management Scenario,


Design 1


3-11.


Emergy Evaluation of the Dispersed Phosphorus Management Scenario,


Design


3-12.

3-13.


Emergy Evaluation of the Concentrated Phosphorus Management Scenario

Emergy Evaluation Summary for Phosphorus-Containing Sources and


Products


3-14.


Phosphorus Management Costs and Basin Phosphorus Outflow for Alternative


Scenarios.


3-15

3-16

3-17


Cost Effectiveness Comparison of Phosphorus Management Scenarios


Service Dollars and Emdollars by Land Use for the Base Case Scenario.


. Comparison of Total Service Dollars and Total Emdollars by Scenario for
Approximately 1.2 Million Acres in the North Okeechobee Basin .


Comparison of Annual Emergy, Service Dollars, and Emdollars per Gram of
Phosphorus by Scenario for the Study Region . . .


Comparison of Total Annual Phosphorus, Emergy, and Emdollars Lost as
Runoff from the Study Region. . . . . .


Summary of Annual Dollar Flows and Emdollar Flows of the Regional


Phosphorus Cycle by Scenario.













LIST OF FIGURES


Figure


page


Energy Systems Diagram of the North Okeechobee Basin with Overlay of Major
Phosphorus Flow Pathways. . . 4

Generic Unit Model of a Land Use Polygon.. . 6


Hypothetical Distributions of Phosphorus and Paid Services ($) as a Function of
Solar Transformity 7


Systems Diagram of the Biogeochemical Cycle of Phosphorus
(Odum, 1983). . . . . .


S S S S S S9


Location Map of Lake Okeechobee and Its Drainage Subbasins


* S f 5 15


Pathways Amenable to Phosphorus Management. 26

Schematic Diagram of a Dairy Waste Management System 32


Land Use and Soil Associations in the North Okeechobee Basin

The Hydrographic Network of Streams (in Blue) and Canals (in Red)


S~ S z1


n the


North Okeechobee Basin


S. . . . 46


Unit Model for Spatial Simulation of the Phosphorus Budget


Unit Model for Key Processes of the CREAMS-WT Program.


= Evapotranspiration; LAI


= Leaf Area Index;


= Rainfal


Phosphorus


S S S S S S S S S S S S S S S S S S S S S S S S 5 51


Model of Phosphorus Assimilation as a Function of Flow Path


Distance


S S S S S S S S S S S 5 S S S S S S S S S S S S S S 5 5 2


Diagram Explaining Emergy Indices (Odum and Odum, 1983).


S 5 S S 61


S~~ ~ S S S







Diagram of Phosphorus Budgets and Their Interactions for the Base Case
Scenario. (a) Energy Systems Diagram; (b) Basin Phosphorus Budget; (c) Beef
Pasture Phosphorus Budget; and (d) Dairy Phosphorus Budget. Units are tons


P/yr (0.9E6 grams P/yr)


Diagram of Phosphorus Budgets and Their Interactions for the Maximum


S . . 67


Phosphorus Use Scenario.


(a) Energy Systems Diagram; (b) Basin Phosphorus


Budget; (c) Beef Pasture Phosphorus Budget; and (d) Dairy Phosphorus Budget.


Units are tons P/yr (0.9E6 grams P/yr).


Diagram of Phosphorus Budgets and Their Interactions for the Predevelopment
Scenario. (a) Energy Systems Diagram: and (b) Basin Phosphorus Budget.
Units are tons P/yr (0.9E6 grams P/yr). . . . . 6


Diagram of Phosphorus Budgets and Their Interactions for the Dispersed
Phosphorus Management Scenario, Design 1. (a) Energy Systems Diagram; (
Basin Phosphorus Budget; (c) Beef Pasture Phosphorus Budget; and (d) Dairy


S. 68


Phosphorus Budget.


Units are tons P/yr (0.9E6 grams P/yr)


Diagram of Phosphorus Budgets and Their Interactions for the Dispersed
Phosphorus Management Scenario, Design 2. (a) Energy Systems Diagram; (
Basin Phosphorus Budget; (c) Beef Pasture Phosphorus Budget; and (d) Dairy
Phosphorus Budget. Units are tons P/yr (0.9E6 grams P/yr) .


Distribution of Imports and Exports of Phosphorus-Containing Materials under


the Base Case Scenario


SLand Use Polygons and Average Annual Phosphorus Runoff Concentrations


under the Base Case Scenario


S S S S S S S S S S S S 77


Land Use Polygons and Average Annual Phosphorus Runoff Concentrations


under the Maximum Phosphorus Use Scenario.


a S 5 5 5 S S 79


Land Cover Polygons and Average Annual Phosphorus Runoff Concentrations


under the Predevelopment Scenario


3-10.


S S S S S SS S S S S 5 81


Land Use Polygons and Average Annual Phosphorus Runoff Concentrations
under the Dispersed Phosphorus Management Scenario . 83


3-11.


Spatial Hierarchy of Runoff Concentration among Land Use Polygons


. 85


3-12.


Land Use Polygons and Average Annual Basin Phosphorus Outflow under the


*0








3-13.


Unit Diagram for Emergy Evaluation of Citrus Land Use under the Base Case


Scenario (E13 sej/ac-yr)


3-14.


S92


Unit Diagram for Emergy Evaluation of Beef Pasture Land Use under the Base


Case Scenario (El 3 sej/ac-yr)


3-15.


93


Unit Diagram for Emergy Evaluation of Dairy Land Use under the Base Case


Scenario (El 3 sej/cow-yr)


3-16.


a a S S S S S S 5 4 5 a S S 9'1


Unit Diagram for Emergy Evaluation of Sugarcane Land Use under the Base


Case Scenario (E13 sej/ac-yr)


3-17


C S S S t S S S S S S S 5 95


. Unit Diagram for Emergy Evaluation of Other Agriculture Land Use (E13


sej/ac-yr).


3-18.


a a a a a a a a a aa a S S a a a S S S 96


Unit Diagram for Emergy Evaluation of Commercial Forestry


(E13 sej/ac-yr)


3-19.


S S 5 S S 6 C S S S S S C a a a a C S 9~7


Unit Diagram for Emergy Evaluation of Urban Land Use


(E13 sej/ac-yr)


3-20.


S S S S S S S S S S S SS S S S S S 98


Unit Diagram for Emergy Evaluation of Basin Scale Treatment for the S-191


Subbasin (E13 sej/yr)


3-21.


3-22.


3-23.


3-24.


3-25.


S S S S S 5 5 a a a a C S S S 5 99


Emergy Summary Diagram and Calculation of Net Emergy Yield and Emergy
Investment Ratios for Major Systems under Each
Scenario . . .


Average Annual Phosphorus Runoff Concentrations and Empower Density
under the Base Case Scenario. . . . .


Relationship between Phosphorus Runoff and Empower Density per Production
Unit 11 .


Number of Phosphorus-Containing Materials as a Function of their
Transformities . . . .


Average Phosphorus Content of Materials as a Function of their


Transformities


3-26.


Relationship between the Emerev per Mass of Phosphorus-Containin2 Materials







3-27


3-28.


. Relationship between the Emergy per Gram of Phosphorus in Materials and
their Spatial Distribution . . . . . .


Relationship between Emdollars and Service Dollars for Land Uses under the
Base Case Scenario. *


Diagram Showing the Full Phosphorus Cycle of the Region (Heavy Black
Lines) with Inputs and Outputs and Internal Cycling under the Base Case
Phosphorus Management Scenario. Dashed Line Represents Flow of Money
Associated with Phosphorus. . . .


Distribution of Phosphorus-Containing Material Inputs and Outputs Based on
the Emergy/Mass Ratios and Spatial Intensity of Phosphorus in the


Materials


Emdollar Flow per Acre Associated with the Annual Change in Onsite
Phosphorus Storage and Annual Runoff Phosphorus under the Base Case


Scenario








EMERGY SYMBOLS AND DEFINITIONS


ENERGY CIRCUIT:


a pathway whose flow is proportional


to the quantity in the storage or source upstream.


SOURCE:


outside source of energy; a forcing function.


STORAGE TANK:


a compartment of energy storage within


the system storing a quantity as the balance of inflows and
outflows; a state variable.


HEAT SINK:


dispersion of potential energy into heat that


accompanies all real transformation processes and storage;
loss of potential energy from further use by the system.


INTERACTION;


interactive intersection of two pathways


coupled to produce an outflow in proportion to a function
of both; control action of one flow on another; limiting
factor action; work gate.


PRODUCER:


unit that collects and transforms low quality


energy under control interactions of high quality flows.



CONSUMER: unit that transforms energy quality, stores
it, and feeds it back autocatalytically to improve inflow.


TRANSACTION:


a unit that indicates a sale of goods or


services (solid line) in exchange for payment of money
(dashed line).


BOX:


miscellaneous symbol to use for whatever unit or


process is labeled.












Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy


BIOGEOECONOMICS OF PHOSPHORUS IN A FLORIDA

By

Carolyn Fonyo Boggess


WATERSHED


December 1994


Chairman:


Major Department:


Odum


Environmental Engineering Sciences


The human economy influences and is influenced by the biogeochemical cycles

of elements, but means for relating chemical cycles to economic systems have been


studied only incidentally.


This study tested ways of relating a chemical cycle to a


regional economy, using phosphorus in the northern drainage basin of Lake

Okeechobee, Florida as an example.

Among the methods used were a mass balance approach to phosphorus

budgeting, dynamic modeling for runoff simulation, cost effectiveness for economic


analysis, and emergy evaluation techniques.


Spatial data on land use and management


practices were organized using a geographic information system.

Phosphorus management scenarios were evaluated and compared in terms of







load reduction to Lake Okeechobee);


economic (i.e., minimize cost of phosphorus


reduction);


and energetic (i.e., maximize regional empower).


Results indicated that


chemical treatment of phosphorus runoff as a point source at subbasin outlets was the


method by which the target load reduction goal could be achieved.


This method of


concentrated phosphorus management was least cost effective at an estimated $190 per


pound of phosphorus removed.


Dispersed treatment of phosphorus through changes in


technology and management onsite at each major source was more cost effective ($11


to $50/lb P removal), though short of achieving the physical goal.


A tradeoff


between


cost and phosphorus treatment efficiency was evident, particularly as the target goal

was approached.

Results of emergy evaluation supported the hypothesis that management

reorganizes the landscape by changing its diversity, and altering the cycling of chemical


elements.


Emergy evaluation showed that the total emdollar loss from the region as


phosphorus runoff was 20 million EM$/yr under the base case scenario, or 1.5 times


the cost of phosphorus control.


The emdollar value of phosphorus outflow from the


region to Lake Okeechobee after assimilation was estimated as 6.4 million EM$/yr, a

measure of its potential use.

Five principles for the new field of biogeoeconomics were proposed for

managing at the interface between an elemental cycle, its role in the environment, and

its economic use to enhance the self-organizing properties of the landscape.












CHAPTER


INTRODUCTION


The economic vitality of landscape systems depends on the biogeochemical


cycling of critical chemical elements.


environmental processes,


Part of each cycle is regulated by natural


while other parts of the cycle circulate through agriculture


and settlements of the human economy generally under development and change.


order to manage important chemical cycles, alternative choices need to be evaluated for


the benefit of the whole landscape, a general problem in ecological economics.


do chemical cycles affect the economy of humanity and nature?


How


This is a study of the


role of phosphorus in an agricultural watershed in Florida, evaluating alternatives for

management.

In the north Okeechobee, Florida, basin, fertilizer and feed inputs that were part

of intensive agricultural developments added phosphorus to a landscape whose runoff


contributed to eutrophication of Lake Okeechobee to its south.


Following public


controversy, many studies were conducted of phosphorus processes in the area.

Drawing on these data and using spatial models, this study first considers the

phosphorus budget of the landscape, its effect on the economy, and the way it changes


with alternative management. Scenarios include those that conserve phosphorus and

reduce flows of phosphorus to the lake. The works of the environment and of the









economy for the various alternatives were assessed on a common basis using energy

(spelled with an "m") evaluation --a method used to determine the aggregate net


productivity of a system.


An economic analysis in dollars was made of the costs of


phosphorus management alternatives.

The overall objective of this research is to analyze the role of phosphorus as an

element in the regional economy of the north Okeechobee basin and to develop a

comprehensive resource management framework for evaluating alternative methods to


reallocate phosphorus in this rural agricultural watershed.


Specific objectives include


(1) Examining the use and spatial distribution of phosphorus in a rural regional

landscape;

(2) Determining the emergy value and economic costs of alternative systems of

phosphorus use; and

(3) Evaluating phosphorus management alternatives based on physical criteria

(i.e., meet target phosphorus goals); economic criteria (i.e., cost effectiveness); and

biogeoeconomic principles (i.e., maximum regional emergy production and use).

General ConceDts


Phosphorus cycling in the environment is a function of both natural processes


(e.g.,


weathering of geologic formations, biological cycling through plant uptake and


senescence, and mineralization of organic matter) and anthropogenic factors (e.g.,


mining, agriculture, and human consumption).


The effect of these processes on the









phosphorus associations with each land use.


The sequence of phosphorus transport


through the basin may be conceptualized as a network of points of concentration and


dispersion.


Phosphorus-containing materials entering the north Okeechobee basin are


concentrated at major processing and distribution points such as chemical plants, feed


suppliers, and supermarkets.


Goods are dispersed spatially throughout the landscape as


inputs to production and consumption processes as determined by land use patterns.

Some phosphorus-containing products resulting from land use activities are again

concentrated at processing centers such as packing plants, livestock markets, and


sewage treatment plants.


Other products may be exported directly from the basin


without further processing (e.g. milk from a dairy operation).

Figure 1-1 is an energy systems overview of the landscape system of the north


Okeechobee watershed.


The components and exchanges are aggregated to include the


phosphorus inflows, phosphorus storing compartments, and the main energy and


economic influences and mechanisms.


The overlay diagram shows just the phosphorus-


containing components and pathways congruent with the whole systems diagram.


emergy and economic evaluations of the whole landscape were made by computing the

main pathways contributing to the system and to the larger outside economy of which

this landscape is a part.

Spatially the landscape consists of several main subsystems, shown as single


units in the overview diagram (Figure 1-1).


In the spatial analyses of phosphorus,





















.0

Sode


Ir I


ac


-4)
3 e
.an"


won,
-v








Figure 1-2 is a unit model of any system defined by polygon boundaries.


Depending


upon the type of land use, some pathways contained zero flows.

Various combinations of alternatives, or scenarios, for management of the

system affecting phosphorus were evaluated either in the aggregate using Figure 1-1 or

spatially for each polygon (Figure 1-2).

Concepts Relating Phosphorus, Emergy, and Economics

The distribution of chemical elements in the universe and in the crust of the

earth is skewed, reflecting the energy hierarchy of the universe's nuclear and other


processes of element formation and distribution.


Thus, there are large quantities of


elements of small atomic weight and fewer of the large atom elements (Schlesinger,


1991).


The distribution of an individual element may be skewed as well.


Much of the


mass is distributed among average concentrations,


whereas small amounts are more


highly concentrated, reflecting the fewer processes in the geobiosphere that maintain

areas of higher concentration.


The theory of self-organization


(Odum, 1992) suggests that processes are


sustained that have useful effects commensurate with their emergy requirement.


theory further suggests that a material that is concentrated will be in a transformity


range where it has a useful effect.


Transformity is a measure of the emergy per unit


energy of a substance, and higher transformity processes may be required where


phosphorus concentrations are higher.


Figure 1-3 suggests a distribution of phosphorus


rnnrnantratmnnc in nrnrsacoc rixeth a mndsrtrat lu hbirh rincp nf trannfnrmi tie













86











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0- 0
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La
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0
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1 100 1E4 1E6 1E8 IE10 1E12 1E14


Solar transformity (sej/J)


Figure 1-3.


Hypothetical Distributions of Phosphorus and Paid Services ($)


as a Function of Solar Transformity.







8

One may surmise that phosphorus at lower or higher concentrations is outside the range

where its utility is commensurate with its emergy requirement.

Transformities are usually higher for processes within the economic systems of


human society than those for processing environmental raw materials.


In other words,


in Figure 1-3, the zone where paid human services operate is in the range of higher


transformities to the right (refer to the hypothetical line for paid services).


At an


intermediate range of transformities where phosphorus is important in economic

processes (e.g., fertilization for agricultural production), it is economically and

energetically effective for moderate levels of paid human services to interact with

phosphorus.


Phosphorus as a Resource


Phosphorus composes about 0.12 percent of the earth's crust (Gilliland,


1973).


It is present in all soils and rocks, in water, and in plant and animal remains (Cathcart,


1980).


The global biogeochemical cycle of phosphorus is illustrated in Figure 1-4.


Phosphorus storage in marine sediments is four orders of magnitude greater than


storage on land.


The phosphorus cycle differs from those of other major elements in


that the atmospheric component is negligible (Schlesinger, 1991).


A major flux of


phosphorus occurs as river transport to the sea (Meybeck,


1982),


which is balanced by


the uplift of sediments.


Humans have linked the economic system to the


biogeochemical cycle of phosphorus mainly through mining phosphate rock for


"'

















































10E12 g/yr


10E12 g


Figure 1-4.


Systems Diagram of the Biogeochemical Cycle of Phosphorus (Odum,1983).









negligible by comparison, localized effects on the primary productivity of nearshore


habitats may be significant (Sandstrom,


1982).


Phosphorus is a vital element in the production processes of natural and human


systems.


It is necessary for photosynthesis, the synthesis and breakdown of


carbohydrates, and the transfer of energy within the plant (Khasawneh et al.,


At background concentrations, it is a valuable, and often limiting


1980).


resource.


concentrations exceeding those required for production, it is sometimes considered a


pollutant.


A pollutant


is, however, merely a resource out of place.


One goal of


ecological engineering at the interface of human and natural systems is to transform

waste products into useful inputs to production, taking advantage of the self-organizing


nature of systems.


Of particular importance in this study is the spatial reallocation of


nutrients from areas of


overabundance to areas of


limitation.


A general overview of


the role of phosphorus in natural and agricultural systems is presented to set the stage

for analysis of phosphorus management alternatives.

Role in Natural Systems


In nature, phosphorus is primarily observed as phosphate mineral, but is chiefly


available to natural plant and animal communities as orthophosphate.


Because of


limited availability and of solubility in aqueous solutions of the geological matrix,

phosphates are quite often a limiting factor for both aquatic and terrestrial natural


ecosystems


(Porcella et al., 1974).


However, Florida lands and waters have a much












Much of the vegetative cover in the north Okeechobee basin is either pineland,


prairie grassland, or wetland.


The flow of phosphorus laden runoff through the


watershed is affected by the occurrence of vegetated wetlands and waterways.

Phosphorus uptake by aquatic and wetland plants transforms bioavailable phosphorus


into storage as plant biomass.


Nutrient release due to senescence of plant matter or


saturation of uptake capacity may pulse the hydrologic system with phosphorus,


particularly at the end of the growing season.


The ability of released nutrients to


stimulate algal production in Lake Okeechobee depends on, among other factors, the


rate of mineralization of organic matter to bioavailable phosphorus.


Management


techniques such as chemical application or harvesting to control aquatic vegetation in

waterways and the use of wetlands for treatment of runoff from agricultural lands

influence the degree and timing of phosphorus outflow to the lake.

Uses in Agriculture

In Florida, agricultural runoff from fertilized cropland accounts for the highest


anthropogenic flow of phosphorus to inland waters (Gilliland,


1973).


Major inputs of


phosphorus to the north Okeechobee basin are accounted for as raw materials used for


fertilizer and animal feed production for agricultural activities in the basin.


majority of the fertilizer produced in the basin is bulk blended; dry granular fertilizer


materials are physically mixed to given N-P-K formulations.

in the basin primarily to improved pasture and citrus acreage.


These mixes are applied

Phosphorus is added to


.~~~~~~ -C.-









The purpose of fertilizer application is to increase the amount of bioavailable


phosphorus in soil for plant uptake.


The amount of phosphorus that can be lost in


sediment or dissolved in runoff water also increases proportionally (Taylor and Kilmer,


1980).


Phosphorus in animal wastes often represents a significant fraction of the total


circulating in agricultural systems.


Thus, a major goal of agriculture in the 1990s has


been to reduce its role in environmental degradation by employing nutrient management

and waste control practices.

Previous Studies of Ecological Economics of Chemical Cycles

Ecological economics studies linking the biogeochemistry of a chemical element


to its role in the human economy are limited.


Odum (1990) indicated that a material


cycle converges as it is incorporated into products, moves to hierarchical centers,

diverges as it is released by consumption, and disperses into less concentrated open


space.


This is certainly the case of phosphorus at the interface with the human


economy in the north Okeechobee basin,


where phosphorus-containing inputs are


concentrated into agricultural products that are transported to processing facilities and


then redispersed for sale as processed goods.


Odum, in the same article,


further


remarked that a systems view is necessary to see the material cycles of the biosphere

and the coupling of all the important processes and energy sources driving the chemical

cycles.


Recently, Pritchard (1992) evaluated the use of a wetland system for treating








using the wetland for treatment versus a more conventional chemical precipitation

method.

Several articles have recently appeared in the ecological economics literature


concerning nitrogen management (Andreasson,


1990; Huang and Uri,


1992; and Gren,


1993).


For the most part, the authors examined alternative policy mechanisms to


reduce the use of nitrogen fertilizer.


Favorable alternatives included crop rotation,


wetland restoration, and marketable nitrogen use permits.


In the same literature,


Erickson (1993) examined the relationship between carbon dioxide emissions and


agricultural yields from a global chemical cycling perspective.


He argued that any


benefits of increased CO, would be more than offset by predicted consequences of

climate change and ozone depletion.

Hutchinson (1952) provided an early quantitative assessment of the phosphorus


cycle in his monograph on the "Biogeochemistry of Phosphorus.


" He examined


phosphorus cycling through the biosphere: in primary rocks, soils, the atmosphere, and


the hydrosphere.


He attributed the return of phosphorus from the ocean to the


activities of birds and humans who retrieve phosphorus by harvesting fish from the sea.

Upwelling of nutrients off the coast of Peru stimulates productivity through the food

chain, ending with birds redepositing phosphorus on land in the form of guano.

Odum (1953) investigated the biogeochemistry of dissolved phosphorus in


Florida waters.


He outlined methods to decrease the potential fertility of waters by


,,,,..:,, ,I,,, 1,,,,., ~:nlnr*:nnl C;lm);nn nrrrl nr\nm; nnln*nn; n;,n,; nn









Gilliland (1973) examined the effects of man's development on Florida's


primitive phosphorus cycle.


She reported that Florida is draining its phosphorus supply


through mining 125 times faster than it is being replaced by dissolution of rock and


reprecipitation.


She concluded that water quality control programs should be based on


the percent effect of a given flow on the overall chemical cycle, rather than setting

effluent standards based on concentrations.

Kangas (1983) studied the interactions of humanity and nature in landforms


affected by phosphate strip mining. He estimated the embodied energy in a spoil

mound and modeled their succession. He recommended managed succession as a more

economical alternative to conventional reclamation. Kangas also modeled the


phosphate fertilizer industry in Florida and calculated a high net energy yield ratio of

12:1 for phosphate fertilizer.

Characteristics of the North Okeechobee Basin


The north Okeechobee basin comprises roughly 1.2 million acres of land in


various uses in south central Florida. This area incorporates 25 drainage subbasins

(Figure 1-5) within four larger drainage regions: Taylor Creek/Nubbin Slough, Lower


Kissimmee River, Indian Prairie/Harney Pond, and Fisheating Creek.

the size of each basin and the drainage region in which each is located.


Table 1-1 lists

For the


purposes of this study, physical characteristics of the area are important in terms of

how they affect land use and the flow of phosphorus through the north Okeechobee














Table 1-1.


Drainage Subbasins of the North Okeechobee Basin.


BASIN NAME AREA, acres REGION


S-65A
S-65B
S-65C
S-65D
S-65E
S-154
S-154C
S-191
L-59E
L-59W
L-60E
L-60W
L-61E
L-61W
LAKE ISTOKPOGA
C-40
C-41
C-41A


FISHEATING
NICODEMUS
L-48
L-49
S-131
S-133
S-135


CREEK
SLOUGH


103350
128310
50450
116590
29160
31620
2180
121820
14410
6440
5040
3270
14290
13570
48350
43960
94930
58500
282300
25080
20770
12100
7160
25660
18090


Lower
Lower
Lower
Lower
Lower
Lower
Lower
Taylor
Indian
Indian
Indian


Indian
Indian
Fishea
Indian
Indian
Indian
Indian


I


immee
immee
immee
immee


issimmee
issimmee
issimmee


River
River
River
River
River
River
River


Creek/Nubbin
Prairie/Harney
Prairie/Harney
Prairie/Harney
Prairie/Harney
Prairie/Harney
ring Creek
Prairie/Harney
Prairie/Harney
Prairie/Harney


Slough
Pond
Pond
Pond
Pond
Pond

Pond
Pond
Pond


Prairie/Harney Pond


Fisheating Creek
Fisheating Creek
Indian Prairie/Harney
Indian Prairie/Harney
Fisheating Creek
Taylor Creek/Nubbin
Taylor Creek/Nubbin


Pond
Pond

Slough
Slough


1 acre =


.4 hectares








Soils and Hydrology

More than 75 percent of the north Okeechobee basin is covered by sandy soils


of varying thickness.

drained organic soils.


The remainder of the area is composed of nearly level, poorly

Urban and residential areas in the basin are underlain by soils


classified as having severe to very severe restrictions for community development and


for operation of septic tanks and landfills.


Furthermore, extensive drainage and


hydrologic control mechanisms are necessary in order to use organic mucklands in the


basin for intensive agricultural production.


Such incompatibilities between soil and


hydrologic characteristics and land use may have contributed to water quality

degradation in the basin.


The dynamics of phosphorus transport through soils,


wetlands, and waterways


in the basin are crucial factors in predicting the effects of phosphorus imports to the


north Okeechobee basin on lake water quality.


Effects of changes in economic uses of


phosphorus on nutrient outflows to the lake depend upon present storage of

phosphorus in soils and wetlands and on the chemistry and timing of release

mechanisms.

Climate and Rainfall


With an average annual temperature of 74 degrees F, the subtropical climate in

the north Okeechobee basin has a major influence on the seasonality of phosphorus use.


Crop selection and cultivation practices,


which are based on climate as well as soil


A nntthr


L,,,, I,,,, :~n~nnc~ nn rrlrnnrr~nrrln nnllrF ;n ,t\;re nnr;rllltllrrll rpn;nn









seasonal impact on phosphorus of the region comes from tourists who increase

phosphorus flow in the form of sewage.

Rainfall serves as a direct input of phosphorus to the lake (16 percent of the


total phosphorus input (South Florida Water Management District [SFWMD],

but it also has indirect effects as an agent of erosion and phosphorus transport.


1989),

The


distribution of rainfall in the north Okeechobee basin varies temporally and spatially.

Average annual rainfall in the basin is about 50 inches, but monthly rainfall ranges

from 6 to 8 inches during the rainy season, June through September, and 1 to 2 inches


during the dry winter months.


Summer rainfall and storm patterns,


which account for


about half of the total annual rainfall, may result in nutrients being flushed into

waterways by dryland flooding.

Physiography

Basin physiography consists mainly of two gently sloping plains, the Osceola


and the Okeechobee.


About two-thirds of the study area has an elevation of 50 feet or


The Bombing Range Ridge located in the northwest corner of the Lower


Kissimmee Basin is the highest point in the study area at an elevation of about 100 feet.


Physiographic features and soils of the basin,


which have been strongly influenced by


its geology, in turn determine the suitability of the area for different types of land use.

Limestone formations, primarily of marine origin, are responsible for the


development of an extensive groundwater system in the region.


The groundwater






19

clays could potentially dissolve and transport phosphorus and eventually become part of


the surface water system.


Phosphorus may also be leached through sandy soils to


become part of the surficial aquifer which is often indistinguishable from surface flow

in the region.

Land Use


Agriculture north of Lake Okeechobee consists primarily of dairy and beef cow-


calf operations,


with limited acreage of citrus and vegetable production (Table 1-2).


Twenty-five dairies with a combined herd of about 26,000 milking cows provide fresh


milk for urban south Florida.


Roughly half of the 1.2 million basin acres is cow


pasture with varying degrees of improvement.


undeveloped upland,


About 40 percent of the basin is


wetland, and native range (see Fonyo et al., 1991 for more detail


on land use in the basin).

Urban land use in the north Okeechobee basin is limited to an estimated 40,000

inhabitants in the City of Okeechobee and surrounding towns, including seasonal


population increases due to tourism.


Most of the transient population is distributed


around the perimeter of Lake Okeechobee in seasonally occupied camps and parks.

Historical trends in land use are important since they may indicate locations


where phosphorus has been stored or built up in soils.


Future changes in phosphorus


usage in the Okeechobee basin depend primarily upon changes in population, land use,

and production practices; on the promulgation of laws governing the use of









Table 1-2.


Land Use Characteristics of the North Okeechobee Basin.


LAND USE AREA (acres)'


Agricultural


Citrus


32000
24000


Commercial Forestry


Dairy (


- 26400 cow


milked)


Barn


Hayfield


5075


High Intensity Area
Milk Herd Pasture
Other Pasture
Solids Spreading Area
Sprayfield
Waste Storage Pond
Improved Pasture


750
3780
11900
4000
4500
1370
480000


Ornamentals


1800
4000
9500
1400


Sugarcane
Truck Crops


Unimproved Pasture
Other Agriculture


160000
150


Urban


Golf Course


Residential (population 40000)
Waste Treatment (1 MGD)
Other Urban


22000
340
8400


Undeveloped
Barren Land


Forested Upland


Rangeland
Wetlands


6200
98000
180000
190000


TOTAL


1.2 million









History of Basin Development

One hundred years ago, south Florida fresh water circulated in a slow, rain


driven cycle of meandering rivers and streams, shallow lakes, and wetlands.


Starting


at a chain of lakes south of Orlando,


water flowed into the Kissimmee River,


meandered 100 miles south into Lake Okeechobee.


During wet seasons,


which


water spilled


over the lake's low southern rim and flowed south across the Everglades saw grass in a

50-mile wide sheet moving at a rate of about 100 feet per day toward Florida Bay


(Boggess et al.,


1993).


Along the Lake's northern shoreline appeared dense stands of water oak,

cypress, popash, and rubber trees. For some 30 miles north of the lake, the landscape


was textured by prairie lands and pine forests. Numerous small pools filled with saw


grass and maiden cane dotted the prairies (Mitchum,


1987).


Modification of the natural freshwater system in south Florida began in the late


1800s as investors began developing the area.


Over the next century, a series of


development, drainage, flood protection, and water supply programs resulted in the


construction of 1400 miles of canals and levees.


The ditching caused oxidation of


organic matter and release of phosphorus from peaty material and from acidic solution

of limestone fragments.

The most important project was the massive, federally funded flood control and

water supply project known as the Central and Southern Florida Flood Control Project


-~~~~r .l ., 4_. n .1 4nLn a *i, -a!n 1 *Lnnnnltnn


nin







22

as C-38; (2) construction of the 25-foot high Herbert Hoover Dike encircling Lake

Okeechobee and providing control over all inflows to and outflows from the lake; and


(3) creation of three water conservation areas south of Lake Okeechobee to store


excess


flood waters and to provide supplemental water supply.

Agriculture first began to develop around Lake Okeechobee in the 1920s.


Originally agriculture was limited by poor drainage and poor soils.


Establishment of


the federal sugar program in the 1960s led to a dramatic increase in sugarcane and


winter vegetable acreage, particularly to the south of Lake Okeechobee.


Dairying,


currently the most important agricultural industry in the north Okeechobee basin, first


began to develop in Okeechobee County in the early 1950s.


Originally, the south


Florida dairy industry had been concentrated around Miami, but urban development

after World War II forced dairymen to move north.

Concerns over water quality in the north Okeechobee basin have spawned three

separate ongoing management efforts: (1) the Kissimmee River Restoration Project,


headed by the U.S. Army Corps of Engineers,


which aims to "restore"


the natural


meandering flow of the River through oxbows and wetlands (Loftin et al.,


1990); (2)


the Lake Okeechobee Surface Water Improvement and Management (SWIM) Plan, a

joint effort of the Florida Department of Environmental Protection (formerly the

Department of Environmental Regulation) and the South Florida Water Management


District,


which was designed to control basin nutrient outflows to the lake in order to






23

Environmental Protection in 1987, requiring dairies to implement specific technologies


to control their discharge of nutrient rich drainage waters.


All other agricultural land


uses are currently subject to permitting and enforcement under the SWIM Plan to meet

target phosphorus discharge standards.

Related Studies of the North Okeechobee Basin


There is a vast knowledge of the Lake Okeechobee ecosystem as a result of


more than two decades of research.


Of particular relevance to this dissertation are


those studies addressing the lake's northern watershed and its impact on water quality.

In the 1970s, the Florida Department of Natural Resources, in conjunction with


the U


Department of Agriculture, conducted a survey of the land and water


resources of the Kissimmee-Okeechobee-Everglades system (USDA,


1973).


information served as a basis for resource management planning for watershed


protection, flood control and protection, and water quality control.


period,


Around the same


Tuan (1973) studied the hydrologic-economic linkages in the same region,


while Baldwin (1975) was surveying practices to reduce nonpoint pollution from

agricultural lands for the Florida Department of Pollution Control.

In 1973, the Florida legislature funded the Special Project to Prevent


Eutrophication of Lake Okeechobee.


The three main objectives of this project were: to


understand and quantify the process of eutrophication in Lake Okeechobee; to

understand quantitatively the inputs to Lake Okeechobee from drainage basins that are

2x A .n..nL.. nnn nn^l .t^ntn rnnnl t m amnl ti n onAI 1-n ,indsrmannt









downstream ecosystem components (Florida Department of Administration,


1976).


Major recommendations of the project were to retain rain water upstream through

storage in wetlands; to reflood publicly owned wetlands; and to improve farming and

ranching techniques.

As part of the Special Project, systems models were developed to shed light on


factors affecting Lake Okeechobee's water quality (Odum and Nordlie,


1975).


regional model was developed and management alternatives were proposed by Fontaine

and Brown, including reestablishment of the Kissimmee River floodplain, onsite

storage and recycle of excess agricultural water, and elevation of stage level in Lake


Okeechobee.


Gutierrez (1977) conducted energy analyses of pasture systems in the


Lake Okeechobee watershed.


Simulation results indicated that improved pasture


operations contributed heavy loads of nutrients to adjacent waterways and are

vulnerable to conditions of fertilizer shortage.

In the 1980s, Bottcher et al. (1986) developed a model to assess the impact of


agricultural practices on water quality and quantity in the


Taylor Creek/Nubbin Slough


(S-191) subbasin.


They used the CREAMS-WT


model to predict nutrient runoff and


developed a basin delivery model to predict nutrient outflow with alternative

management practices.

Following this effort, the South Florida Water Management District funded

research on the Biogeochemical Behavior and Transport of Phosphorus in the Lake









the soil to retain phosphorus; to determine how phosphorus moves through the soil

from the site of deposit; and to develop an inventory of all phosphorus sources to the


lake basin.


This contract was amended to determine the availability and cost


effectiveness of management options to reduce phosphorus loads to Lake Okeechobee

and to develop an integrated decision support system for evaluating alternative

combinations of phosphorus control practices to achieve phosphorus reduction goals


(Fonyo et al.,


1993a).


This dissertation research is a byproduct of the contract


amendment.


Phosphorus Management Alternatives


Alternative ways to manage phosphorus include an array of onsite, physical

changes in production practices, onsite treatment alternatives, and regional treatment


options.


Combinations of alternatives, or scenarios, may be used in a coordinated


manner for basin-wide management (Porcella and Bishop,


1974).


To be technically effective, phosphorus management alternatives must

physically change phosphorus flows through agricultural and other systems by either

(1) reducing phosphorus material imports/sources, (2) increasing onsite

storage/treatment, (3) enhancing phosphorus product exports, or (4) increasing offsite


storage/treatment.


Figure 1-6 illustrates these options.












Source Reduction


Phosphorus flows through a production system may be altered by adjusting the

amount of phosphorus-containing materials that are imported to the system from outside


the system boundaries.


Source reduction can be achieved via several mechanisms


including (1) input substitution, (2) increased technical efficiency, (3) technological


change, (4) output substitution, (5) reduced production levels, and (6) recycling.


Input


substitution entails substituting low concentration inputs for higher concentration


inputs.


Examples of input substitution include substituting feed ration ingredients with


high phosphorus concentrations with lower phosphorus concentration ingredients while

maintaining the same nutritive value and substituting detergents without phosphorus for

phosphorus-containing detergents.


Increased technical efficiency,


via better management of existing technology,


may increase agricultural output per unit of phosphorus input.

testing may reduce fertilizer required to produce a target yield.


For example, soil

Reduction in the


phosphorus concentration of dairy feed rations as an outcome of research is another


example.


Under technological change, on the other hand, a more efficient production


technology is adopted.


For example, alternative fertilizer application methods (e.g.,


banding instead of broadcasting) may be adopted.

Sources can be reduced by changing to processes that require less phosphorus.

For example, production of certain goods may be discontinued (e.g., dairy easement).
t U f^m pfl." \









However, potential tradeoffs exist.


Phosphorus may be reduced at the expense of


increasing the use of other agricultural chemicals.


Additionally, an increased supply of


substitute goods may not be economic.


Recycling is another form of source reduction,


where phosphorus-containing


materials originating within a production system are substituted for phosphorus-

containing imports (e.g., nutrients in livestock manure substituted for commercial

fertilizer imports or purchased feed rations).

Onsite Treatment/Storage


Another way to reduce the outflow of phosphorus is to increase onsite storage of


phosphorus.


Onsite storage can be increased by (1) facilitating natural chemical


bonding of phosphorus to soil particles (e.g., use of lime), (2) increasing the spatial

distribution of phosphorus (e.g., grazing herd management), (3) increasing the

temporal distribution of phosphorus applications (e.g., split fertilizer applications), (4)

reducing water flows and thus phosphorus mobility (e.g., irrigation management), (5)

detention/retention of runoff with associated assimilation, recycle, or treatment (e.g.,

impoundments or wetland filters), or (6) constructing a chemical or biological treatment

plant.

Exoort Enhancement


A third, though less important, method to impact the flow of phosphorus is to


enhance the export of phosphorus-containing products.


To be effective, the increased






29

exporting crops (e.g., sod), (2) transformation of byproducts into saleable phosphorus-

containing goods for export from the watershed (e.g., composted dairy manure), and

(3) dispersal of phosphorus-containing byproducts outside the watershed (e.g., sludge

hauling).


Offsite


Treatment/Storage


Finally, phosphorus outflow can be reduced by increasing offsite storage,


intercepting runoff before it reaches Lake Okeechobee.


Offsite storage can be achieved


by (1) detention/retention of runoff with associated assimilation, recycle, or treatment


(e.g.,


wetland filters) and (2) aquifer storage and recovery.


Other options include


chemical or biological treatment at central collection points and diversion of runoff out


of the watershed.


Offsite treatment and storage options are referred to in this study as


basin scale alternatives.


Description of Scenarios


Scenario evaluations are like controlled experiments, showing the consequences


of specific changes,


while keeping other conditions constant.


Five phosphorus


management scenarios were examined in this study: base case phosphorus management,

maximum phosphorus use, redevelopment, dispersed phosphorus management, and

concentrated phosphorus management.

Base Case Phosohorus Management Scenario


The base case scenario represents land use and management practices in the


.1~m tS; I. I I- .~r Inn-i Inn


.1 r\i 1 I ~. 1.. 1 nn~









Table 1-3.


Management Practices for the Base Case Scenario (1993 Conditions).


LAND USE


MANAGEMENT PRACTICE


Improved pasture


11 lbs P/ac-yr fertilizer; dry season application;


no fencing; 2.5 acres/cow


Unimproved pasture/rangeland


no fertilizer; no fencing;


16 acres/cow


Citrus


9 lbs P/ac-yr fertilizer; mature groves; drip
irrigation; no impoundment


Sugarcane


17 lbs P/ac-yr fertilizer for plant cane, first and
second ratoon crops; 61 lbs P/ac-yr applied
to sweet corn in rotation


Ornamentals


42 lbs P/ac-yr fertilizer


87 lbs P/ac-yr fertilizer


Commercial forestry

Sod


Dairy


no fertilizer

44 lbs P/ac-yr fertilizer


8 dairies low technology; effluent to sprayfield;
solids landspread
1 dairy low technology plus ecoreactor
11 dairies semiconfinement; effluent to sprayfield;
solids landspread
4 dairies semiconfinement; effluent to sprayfield;
solids composted and sold
1 dairy confinement; effluent to sprayfield; solids
composted and sold


lb/ac =


1.1 ke/ha


Truck crops


~____






31

citrus, and ornamental plants employed normal or "typical" management practices

basinwide as determined from interviews with land owners and county extension agents

in the area (refer to Fonyo et al., 1991, for discussion).


Of the


dairies still operating in the basin, nine were classified as low


technology, or the minimum requirement to meet Dairy Rule regulations.


These


designs consist of an effluent collection system with a lagoon for storage and a


sprayfield for dispersion of nutrients onto cropland.


waste management system is given in Figure 1-


A schematic diagram of a dairy


Solids are landspread on designated


pasture areas.


One of these low tech systems also has an "ecoreactor"


which is a


biochemical treatment system consisting of an integrated three step phosphorus removal

process: chemical precipitation, microbial cell uptake, and aquatic plant uptake in a

constructed wetland.


Fifteen dairies were classified as semiconfinement systems.


low technology


They differ from


in that the milking herd spends less time in the designated pasture and


a greater proportion in the high intensity area or feed barn.

greater waste control and phosphorus recapture. One dair)


This design allows for


t in the basin constructed a


total confinement system in which the milking herd is restricted to the feed barn or


milking parlor.


Five dairies sold their solids as compost, rather than reapplying to


pasture.

Maximum Phosphorus Use Scenario


-~~~nr i*












were applied to each acre of improved beef pasture annually, as compared to 11 lbs


P/ac-yr in 1993.


More recent information has suggested that not all improved acreage


is fertilized each year, and the actual percentage of the total acreage may vary as a


function of beef prices.


For the purposes and the modeling efforts of this study,


however, the above assumptions were maintained.


Forty-one dairies,


with a combined milking herd of 33,400 cows,


were


operating before the Dairy Rule legislation went into effect.

dairies in 1987, the average milk herd size was 815 cows, v


to 1040 cows per dairy in 1993.


Though there were more


vhich increased 28 percent


The average phosphorus content of dairy feeds was


0.5 percent, compared to 0.45 percent in 1993.

Prior to the Dairy Rule, milk cows roamed freely in pastures and waterways


when they were not in the barn or high intensity area.


Milk herd pastures comprised


45 percent of the dairy land area in 1987, compared to 12 percent in 1993.


No formal


phosphorus control methods were used other than lagoon storage of barn wash water.

Predevelooment Scenario


At the turn of the century, the north Okeechobee landscape was a mosaic of


upland and wetland habitats with natural drainage along marshy sloughs.


Human


settlements in the region were probably limited to scattered indian tribal populations

with minor phosphorus-related activity.

A map produced for an environmental study of southern Florida (Odum and









As a rough estimate, the region comprised 700,000 acres of forested and nonforested


wetlands


, 350,000 acres of grassy scrubland, and 190,000 acres of forested uplands.


Steady state conditions were assumed in upland systems so that the


concentration of phosphorus released in organic matter was equal to the rainfall


phosphorus concentration taken up by upland vegetation.


phosphorus concentration of 0.04


An average rainfall


mg P/1 from Sculley (1986) was assumed.


redevelopment concentration may actually have been even lower since atmospheric

deposition by sugar mills and phosphate mining operations in central Florida may be


contributing to current levels.


Wetlands were assumed to be phosphorus sinks by


accumulating organic matter and building peat.


Thus


, the runoff phosphorus


concentration from wetlands was set equal to zero.

Dispersed Phosphorus Management Scenarios

The dispersed phosphorus management scenario refers to maximum phosphorus


control spatially at each source.


Two variations of this scenario were tested by


changing the type of control on dairies.


In both cases


improved beef pasture was


fenced to keep cows out of waterways; impoundments to capture runoff were added to


all citrus acreage; and rice was grown


in rotation with sugarcane.


Base case conditions


were assumed otherwise.


Under the first maximum control design (design 1),


to confinement systems,


dairies were converted


with sprayfields for effluent treatment and solids applied to







35

biochemical treatment system (ecoreactor) for effluent treatment and solids composting

for sale and export out of the basin.

Concentrated Phosphorus Management Scenario

As an alternative to managing phosphorus onsite, phosphorus leaving a drainage


basin as outflow may be treated as a point source.


Chemical treatment was applied at


basin outlets for each of six drainage subbasin whose average annual phosphorus levels

exceeded 10 tons/yr, based on Lake Okeechobee Surface Water Improvement and


Management data (SFWMD,


1989).


All of the remaining dairies are located in three


of these subbasins: S-191, S-154, and S-65D;


two subbasins are highly channelized,


C-40 and C-41; and Fisheating Creek covers a large geographical area.

Each 200 million gallons per day (MGD) chemical treatment plant uses alum to


precipitate phosphorus at 89 percent removal efficiency.


An 8800 acre in-lake flow


equalization basin is required for each system to provide a steady flow rate for


treatment (DER,


1986).


Though originally designed for the S-191 basin outlet, the


same operating costs and parameters were applied to all basins as a ballpark estimate.

Dissertation Plan


In this study, data on the regional agricultural system of the north Okeechobee


basin were assembled and entered into a geographic information system.


Then


biogeochemical budgets for inputs and outputs of phosphorus were prepared under

different management scenarios and the role of phosphorus in the biogeoeconomic









example, principles were tested regarding the role of critical limiting materials in the

self-organization of biogeoeconomic systems.

In the next chapter, methods are presented for performing phosphorus

budgeting, emergy analysis, economic evaluation, and scenario comparisons of


phosphorus management alternatives. Phosphorus budgeting, energy evaluation, and

economic analysis results are given in Chapter 3. In Chapter 4, the relationship


between the phosphorus cycle, energy, and economics is examined, including


implications for phosphorus management.


General principles of biogeoeconomics are


proposed and suggestions are offered for future related research.












CHAPTER


METHODS, PROCEDURES, AND
SOURCES OF DATA

Five sets of procedures were used in this regional study of phosphorus: (1)

organization of data with the ARC/Info geographic information system; (2) phosphorus

budgeting; (3) emergy evaluation; (4) economic analysis; and (5) scenario comparisons.

Organization of Data with the ARC/Info Geographic Information System

Data for the north Okeechobee basin were entered into the ARC/Info


geographic information system for computer processing.


Because aggregation is


required, the process of categorizing data spatially is a form of modeling.


ARC/Info


was used to automate, manipulate, analyze, and display geographic and other data on


the regional system.


The data used in this work were entered in files that were part of


LOADSS (Lake Okeechobee Agricultural Decision Support System), a decision support

system in ARC/Info designed to assist water managers concerned with eutrophication of


Lake Okeechobee (Fonyo et al.,


1993a).


Spatial data have physical dimensions and geographic location, and are


composed of landscape features which may be represented on a map.


Spatial data were


entered in three forms: points (e.g., cities), lines (e.g., roads), and polygons (e.g.,


land area).


A coverage is a digital version of a map, or a homogeneous class of data









within a map,


which contains locational data (i.e., defines points, lines, or polygons)


and attribute data (i.e., describes points,


lines


, or polygons) about each map feature.


LOADSS utilizes a number of coverages during its operation.


The main


coverage,


referred to as LO COMP


, contains more than 7000 polygons.


It was created


by combining an edited version of the District'


coverage, STATSGO (State Soi


1987 land use coverage,


Geographic Data Base) soil associations,


dairy

weather


regions,


and political boundaries.


Hydrography data indicate drainage pathways from


each individual basin to Lake Okeechobee.


Land Use


Coverage Description


As part of the District contract "Biogeochemical Behavior and Transport of


Phosphorus in the Lake Okeechobee Watershed"


, a digitized


987 land use data base


was provided by the District in Autocad format for each USGS quadrangle in the study


area on a scale of 1:24,000.


The quads were converted to ARC/Info format, then


edgematched,


mapjoined,


and clipped to form one continuous data base for the


watershed.


These data were verified as part of Area 3 of that


contract.


Some changes


were made to the land use tags to accommodate the phosphorus budget analysis.


Certain Level


land use codes were changed to Level 3.


For example AP (agricultural


pasture) was changed to either APIM (improved pasture) or APUN (unimproved


pasture).


New land use tags were created to differentiate phosphorus related activities.


Details of the procedures and information sources used to verify the land use data are









For this study, land use tags were grouped into the following land use

categories: barren land, citrus, dairy, commercial forestry, forested uplands, golf

course, improved pasture, ornamentals, other agriculture, other urban, rangeland,


residential, sod farm, sugarcane, truck crops, unimproved pasture,


waste treatment


plant,


water bodies, and wetlands.


A land use map for the study area is given in


Figure


The redevelopment land cover map for the low energy scenario evaluation was

generated in ARC/Info by interactively changing polygon types using the LOADSS

model.

Soils Coverage Description

The STATSGO soil association coverage was produced by the Soil Conservation


Service in 1991.


The data are 1:250,000 scale quadrangles of major soil associations,


or groupings of soil types.


The data were converted from Lambert to State-Plane


coordinates for use in the study area.

STATSGO is used mainly for large scale resource planning, management, and

monitoring since the data were created by generalizing more detailed soil survey maps.

Map unit composition for STATSGO was determined by sampling areas on more

detailed maps and expanding the data statistically to characterize the whole map unit.

The fundamental identifier for a map unit or soil association is referred to as its MUID


(Map Unit ID).


Soils attribute data were used for CREAMS-WT runoff simulations.




























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Weather Coverage Description

Four weather regions were differentiated based on rainfall patterns in the


watershed: North


South


and West.


Weather regions were specified for runoff


simulation modeling using the CREAMS-WT


model.


Boundary Coverages Description


Maps of spatial boundaries,


such as drainage basins,


regions,


and counties


were


used for spatial scale delineation.


All of the boundary coverages were provided by the


South Florida Water Management District (SFWMD) in either Autocad or ARC/Info


format.


These boundaries are consistent with those used in the 1989 Interim Lake


Okeechobee Surface Water Improvement and Management (SWIM) Plan Technical


Document (SFWMD,

Dairy Land Use Cove


1989).


rage Description


The original land use data base only provided information about the location of


the dairy barn and not the other land uses within a dairy boundary.


Dairy land uses


were digitized by the South Florida Water Management District for 43 preDairy Rule


(1987) and


current (1993) dairies in the watershed.


Land use tags were created for


each land use type on the dairies that have installed waste treatment systems and remain


in operation.


Table


1 gives


ist of dairy land uses and tags assigned to dairy


coverage polygons.

Hydrography Coverage Description


rW~~~~~t~ AS. l I. *' I U *, I. *


nn rnnnl










Table 2-1.


Dairy Land Uses


and Land Use


Tags Assigned to Dairy Polygons.


DAIRY


TAG


DAIRY LAND USE


BARN


Milking barn or parlor


all imports and exports of materials are


attached to this


and use:


High intensity area; area surrounding barn used as a holding area


and sometimes feeding area


MHP


Milking herd pasture; the milking herd is restricted to this pasture
area when not in the HIA or barn; the typical maximum animal
density of the MHP is 4 to 6 cows per acre


SPFL


Sprayfield


part of the waste management system


effluent from


the waste storage pond is applied usually through a center pivot
irrigation system to this forage production area at a rate not to


exceed plant uptake (60


bs P/ac/yr)


Solids spreading area; solids that are scraped from the barn area,


or occasionally dredged from the waste storage pond,
by spreader to this designated field area


are applied


OTP


Other pasture; includes pastures for pot (sick) herd,


springers,


and heifers and calves, if they are raised onsite; the typical


maximum animal density in these pasture areas is about


cows


per acre


OTFL


Other field


hay field or other forage production area with no


animals


OTL


Other land


includes roadways and structures


WET


Wetlands within dairy boundaries


WSP


Waste storage pond; area where wastes from the barn and high


1 r .









and related hydrographic features


" (USGS, 1985).


The digital line graphs (DLGs)


produced by USGS contain hydrographic features with the following attributes: length

in feet; major code, indicating the type of DLG (050 for hydrography); and minor


code, used to describe the hydrographic features including nodes,


areas, lines, sing


points,


general purpose and description codes.


Minor codes that appear in the


hydrography data base within the study area boundaries are given in Table


purposes of phosphorus budgeting in this study


For the


minor codes were reclassified into two


groups: wetlands and canals (see Figure 2-2).

The original hydrography data base for the study area was digitized from 1972


USGS quadrangles.


Regional drainage patterns have


changed significantly over the last


twenty years.


Hydrography data were updated with the help of South Florida Water


Management District field personnel familiar with drainage patterns in the study area


and 1984 Mark Hurd aerial photos.


"canal


Arcs were classified as either "wetlands


using the National Wetlands Inventory (NWI) as a background coverage for


verification.

Phosphorus Budgeting

The flows and storage of phosphorus in the drainage basin were studied by


imulating a spatial model using a


implified unit model.


The unit model for


phosphorus in the agricultural landscape (Figure


-3) was evaluated for each polygon,


including the flows between polygons and exchanges across watershed boundaries.









Table


Hydrography Attribute Codes and Arc Length Classifications.


MINOR CODE DEFINITION CLASSIFICATION


200 Shoreline Wetland
202 Closure line Wetland
204 Apparent limit Wetland
407 Canal lock or sluice gate Canal
412 Stream Wetland
414 Ditch or canal Canal
605 Right bank Canal
606 Left bank Canal
610 Intermittent Wetland




















































































~t4


Crr --- as, a -r I *. I'T'L. -- r /. I! t I fl n


Lircur


IT-I






















Rain


Stored in


Polygon Area


Phosphorus
Export


Offsite flow


ASp=


- SEp


-Op


Figure


Unit Model for Spatial Simulation of the Phosphorus Budget.


Assimilated
from Other


Sector Outflows









phosphorus uptake and storage (assimilation) in wetlands and canals


from each polygon


to Lake Okeechobee.

A simple annual mass balance approach was employed to examine the use and

fate of phosphorus in the north Okeechobee basin under alternative phosphorus


management strategies.


A similar approach was adopted by Porcella and Bishop (1974)


in their analysis of phosphorus management in the Great Lakes basin.


balance equations,


The basic mass


which assume a one year time step is adequate, are applied at the


polygon level and may be expressed as


AIS,


-CEE,


= Op


where:


= average annual polygon phosphorus retention or storage, tons/yr
= average annual phosphorus imports to polygon p, tons/yr
= average annual rainfall phosphorus for polygon p, tons/yr


EE,


= average annual phosphorus exports from polygon p,


tons/yr


Op = average annual runoff phosphorus from polygon p, tons/yr
Ap = average annual phosphorus assimilated offsite from polygon p,
tons/yr
L, = average annual basin phosphorus outflow attributed to polygon
p, tons/yr

Phosphorus enters each polygon of the basin in goods used for production or for


local consumption, and in rainfall.


It leaves an individual polygon as either an


exported product or in runoff water.


Simply stated,


the change in phosphorus storage


onsite is the difference between the net import of phosphorus-containing materials plus


+ R,


A,









assimilated along the flow path through plant uptake and soil adsorption,


remainder discharged to Lake Okeechobee.


with the


Thus, there are basically two components


to phosphorus retention within the basin: onsite storage and assimilation along the flow


path to the lake.


Basin phosphorus retention is a function of rainfall, soil type,


standing biomass, drainage density, distance upstream, and management practices.

Such factors introduce elements of spatial variability in the data that are not captured by


aggregate analysis based on general land use categories.


Analysis using spatial


modeling techniques accounts for such variability.

Phosphorus Imports and Exports

Imports and exports of phosphorus-containing materials by land use type are

based on "typical" practices as gleaned from interviews with farmers, feed and


fertilizer suppliers, county extension agents, and state and federal agencies.


Published


documents, such as agricultural censuses, extension recommendations, fertilizer

consumption reports, and state production statistics were used to verify interview data


results.


Details of the data collection procedures and phosphorus import and export


data are given in Fonyo et al. (1991).

Phosphorus in rainfall was estimated as 1.13 lbs P/ac-yr basinwide on an


average annual basis.


(Heatwole,


This figure was based on a rainfall concentration of 0.1 mg P/I


1986) and an average annual rainfall of 50 inches (Sculley, 1986).


Phosphorus Runoff from Agricultural Sectors









results represent the


"edge-of-field" runoff for each agricultural polygon.


The unit


model is represented in Figure 2-4.

Agricultural runoff simulation generates phosphorus loading for varied weather,


soil, and phosphorus management combinations.


CREAMS-WT


was chosen to model


phosphorus movement on a field scale because of its ability to successfully simulate


nutrient transport through South Florida's spodosols (Heatwole et al.,


1988).


Further


detail on CREAMS-WT and modeling procedures are given in Kiker et al. (1992).

The purpose of the simulations performed with CREAMS-WT was to evaluate

the expected impact of alternative management practices on phosphorus runoff from


individual fields (polygons) with a specific land use.


All possible combinations of


management practices with land use, soil association, and weather region could not be


evaluated.


A subset of the most typical, or commonly used, management practices was


selected and simulated over twenty years of stochastic weather data for each appropriate

land use, soil, and weather combination within the north Okeechobee basin (refer to


Fonyo et al.,


1993a).


Average annual runoff volumes and phosphorus loads were


generated by CREAMS-WT for each unique combination; from these, average runoff

concentrations were calculated.

Phosohorus Assimilation by Wetlands and Canals


Another submodel was used to estimate phosphorus assimilation in canals and


wetlands from each polygon to Lake Okeechobee.


Diagrams and equations are given in







































O cU
'fl
U'-



a. -


ot+


cnQU
i ci


I-I
L4I



























































-ml
*


*

i 4)


* a

2


4 I,


.II 1s!


cCu
ii3
>0LL









pathway distance, each type of pathway having a different linear coefficient.


The final


equation is appropriate where the flows through several types of surfaces are in series.


Assimilation follows


the equation which is consistent with the Lake Okeechobee


SWIM Plan:


-0 ,


* e-(OVR


+ WET + (TAN))


= Op


where:


Lp = average annual basin phosphorus outflow attributed to polygon
p, tons/yr
Op = average annual runoff phosphorus from polygon p, tons/yr
Ap = average annual phosphorus assimilated offsite from polygon p,
tons/yr


OVR
WET
CAN


= overland P assimilation
= wetland P assimilation
= canal P assimilation =


= ao OLL
= aw WLL


ac CL


= overland flow assimilation coefficient, mi-1


OLL


default


= overland flow distance, or the distance from each polygon


centroid to the nearest wetland or canal, mi
aw = wetland flow assimilation coefficient, mi1


WLL


= wetland flow distance, or the cumulative length of al


wetland


segments from each polygon to basin outlet, miles
ac = canal flow assimilation coefficient, mi'
CL = canal flow distance, or the cumulative length of all canal segments


from each polygon to basin outlet,


miles


Calculation of flow oath distance


The algorithm developed to calculate flow path distances from each polygon to


its subbasin outlet was performed externally from LOADSS.


The ARC/Info 6.0


procedure which was used to calculate canal (CL) and wetland (WLL) drainage

distances is as follows:










3. Run the NEAR command and store distances from polygon centroids to
nearest stream nodes in the hydrography data base;
4. Store stream inlet node numbers for each centroid; and
5. Use the PATH command in the ROUTE algorithm to calculate wetland and
canal lengths from the inlet node for each polygon centroid to the appropriate
basin outlet node.

Calibration of phosphorus assimilation coefficients

A series of steps were taken to calibrate phosphorus assimilation coefficients

based on historical basin phosphorus outflow data as reported in the Lake Okeechobee


SWIM Pla

(1993b).


in.


Calibration procedures and results are documented in Fonyo et al.


Rather than assigning one assimilation coefficient each for wetlands


(0.64/mile) and canals (0.04/mile) basinwide as in the SWIM Plan, individual


coefficients were estimated for each drainage subbasin.


information on in-stream processes,


Because of a lack of


wetlands and canals were assigned the same


coefficient by subbasin, and overland flow assimilation was forced to zero.

Coefficients are listed by subbasin in Table 2-3.

Basin Phosphorus Outflow


Basin phosphorus outflows attributed to individual polygons were calculated as


the difference between runoff and assimilation.


Basin outflow from individual


polygons were summed by subbasin for comparison with SWIM Plan data.

Emergy Evaluation

The contributions of environmental and economic (purchased) resources to the

nm A u nnnlrnr, an n *ka .. rn^n..nt an Dana a. ra 1 I. A nl n n m L W k f f-









Table 2-3. Phosphorus Assimilation Coefficients and Average Flow Path Lengths by
Drainage Subbasin in the North Okeechobee Basin.


BASIN
NAME


ASSIMILATION
COEFFICIENT
(mile-')


AVERAGE
CANAL
FLOW PATH
LENGTH (mi)


AVERAGE
WETLAND
FLOW PATH
LENGTH (mi)


C-40
C-41
C-41A
Fisheating Creek
L-48
L-49
L-59E&W
L-60E&W
L-61 E&W
Lake Istokpoga
Nicodemus Slough
S-131
S-133
S-135
S-154
S-154C
S-191
S-65A
S-65B
S-65C
S-65D
S-65E


10.3
2.2
1.5
1.2
3.7
6.6
0.2
7.0
3.4
11.0
3.5
9.8
4.0









stepward transformation in a production process.


The more steps, the more energy it


takes to make a product.


However


, energies of different type have differing abilities


to contribute to production.


step,


By keeping track of the energy inputs required along each


expressing them in units of one kind of energy, one has a measure of the total


resource used for a product or service.


This method measures energy "embodied" in


work previously completed to make a product.


Emergy, spelled with an "m"


with the unit emjoule,


is defined as the available


energy of one kind previously used directly and indirectly to make a product.


When


expressed as solar energy, the measure is solar emergy in solar emjoules (Odum,


1986;


Scienceman


,1987).


Solar emergy can be used as an aggregate measure of the net


productivity and resource uses of a system.


The emergy per unit energy is called the


transformity and is a measure of energy quality and position in the energy hierarchy.

Emergy flow per unit time is defined as empower.


Emergy contributions are determined for nature'


work


, for purchased


resources


, and for human services (Odum and Arding,


1991).


The work of the natural


system is integrated into the analysis of phosphorus management alternatives in two


ways:


(1) as inputs to the agricultural production process,


and (2) as estimated by the


amount of residuals assimilated by wetland and aquatic ecosystems


in the watershed.


The first step in emergy analysis of phosphorus management alternatives was to

construct an overview diagram of the entire north Okeechobee basin and then of each









and emergy units and in emdollars.


Emergy evaluation tables were constructed with


the following columns


Column 1:


Column


Column 3:

Column 4:


Line item number to signify the footnote for calculations.

Item name as indicated in the diagram.

Raw data in joules, grams, or dollars.

Transformity, or the emergy required to generate a unit of product,


in solar emjoules (sej) per unit.


Column


Column 6:


Solar emergy; the product of columns 3 and 4, in solar emjoules.

Emdollar (formerly macroeconomic dollar equivalent); calculated


by dividing emergy in column 5 by the emergy/currency (emjoules/dollar) ratio.
The emergy/currency ratio is obtained by dividing the gross national product in
given year by the total emergy used by the country that year (Odum and


Arding,

Column


1991).


Phosphorus content of item, in grams


Column 8: Emergy/mass ratio of phosphorus, or the emergy required to
generate a gram of phosphorus in the product, in solar emjoules per gram.


Economic Analysis


Economic analysis in this study was limited to determining the cost effectiveness

of phosphorus management alternatives as measured by the dollars spent per unit of


phosphorus reduction in basin drainage waters.


employed.


A partial budgeting approach was


Only direct investment, operation and maintenance, and secondary costs1


incurred by the producer due to changes in management were estimated.


Investment


costs were estimated as the total one-time costs (materials and labor) to install a new










phosphorus management technology.


Investment costs were annualized over the life of


the technology assuming an interest rate of 10 percent (the prevailing rate at the time of

the study) using the following equation:


+0i"


where:


= annualized investment, $/yr
= present value of total investment, $
= prevailing interest rate
= life of investment, years


Operation and maintenance costs were calculated as the annual costs to keep the


phosphorus management technology functional.


In most cases, these cost components


were taken from engineering design reports (refer to Appendix A).

Two types of secondary costs were estimated: production costs and output


effects.


Production costs reflect changes in existing annual cost components incurred


as a result of adopting a phosphorus management alternative.


For example, changing


the rate of fertilizer application results in either an increase or decrease in annual


operating costs.


The output effect reflects changes in output of a product as a result of


adopting a phosphorus management alternative.


An example is a change in milk


production due to structural change (e.g., confinement) on a dairy.


Secondary costs


may be positive or negative. Relationships between changes in management and costs

and returns are given in Appendix A. The basic costs of operation without phosphorus


management, which were needed for emergy evaluations,


were obtained from various


P "


+ i)"







59

In order to facilitate aggregate cost effectiveness analysis at the watershed scale,

certain homogenizing assumptions were made about the characteristics of specific basin


activities and management practices. Appendix A outlines these assumptions, the

methods for calculating direct costs (investment, operation and maintenance, and


secondary) in 1990-91 dollars, and data sources for pertinent nonpoint land uses (beef


pasture, dairy, citrus, sugarcane)


point sources (sewage treatment plants), and basin


scale treatments (aquifer storage and recovery, biological treatment, chemical

treatment, diversion).


Scenario Comparisons


One of the purposes of this study was to consider management alternatives that

would reduce phosphorus outflows from drainage subbasins to predetermined average


annual values.


Five phosphorus management scenarios (combinations of alternatives)


were compared to determine which minimized basin phosphorus outflow, minimized

the cost of phosphorus reduction, and maximized empower (emergy per year) on a


regional scale.


Scenarios were chosen to represent a range of intensity of phosphorus


use and management.

Cost effectiveness analysis is a useful way to perform an economic evaluation of


two scenarios.


Cost effectiveness was defined as the dollars spent per unit reduction of


phosphorus in basin outflow.


Cost effectiveness was calculated for a two scenario


comparison as the change in total direct costs divided by the change in basin









changes in factors of production or output were included in the cost effectiveness


estimation.


A negative sign in the denominator indicates that basin phosphorus outflow


was reduced under the current scenario.

Phosphorus runoff concentrations (mg/l) from land areas and phosphorus

outflows (tons/yr) from drainage subbasins were compared to target goals that were


specified


in the Lake Okeechobee SWIM Plan (SFWMD, 1989).


These physical


criteria gave another measure of the success of a management scenario.

Scenarios were also compared to determine which design maximized the use and

feedback of phosphorus throughout the regional landscape. Emergy indices provided


such means for comparison.


Several indices were proposed by Odum and Arding


(1991) to analyze shrimp mariculture in Ecuador.


These indices are also useful for


comparing phosphorus management scenarios for the north Okeechobee basin.


Each


index is defined briefly (refer to Figure 2-6 for illustration):

Solar transformity the equivalent solar energy that would be necessary to
generate a unit of resource efficiently and rapidly; sej/j.


Emergy per unit mass


material


- energy of one type required to generate a unit mass of


sej/g.


Emergy investment ratio the ratio of emergy fed back from the economy to the
free emergy inputs from the environment; F/I.

Net energy yield ratio emergy of an output divided by the emergy of the


inputs that are from the main economy (i.e., purchased);


Y/F.












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61
















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CHAPTER 3
RESULTS


Results of the evaluation of phosphorus budgets, dollar costs, and emergy are

given for each of five phosphorus scenarios: base case phosphorus management,


maximum phosphorus use, redevelopment,


dispersed phosphorus management,


concentrated phosphorus management.

Phosphorus Budgeting

Phosphorus budget results are summarized by land use in Tables 3-1 through 3-4 for


each relevant scenario.


Budget components are also summarized diagrammatically in


Figures 3-1 through 3


by scenario.


The energy systems diagram illustrates the


coupling of the hydrology of the region to the flow of phosphorus through it.

Phosphorus sources are indicated as environmental inputs to the left of the diagram and


purchased


imports from the top.


Tanks indicate storage of phosphorus, both onsite in


soils and biomass, and offsite through assimilation in canals and wetlands.

Phosphorus Imports and Exports

Figure 3-6 summarizes annual imports and exports of phosphorus containing

materials across north Okeechobee basin boundaries under the base case scenario.


Imports are primarily fertilizer and dairy feed,


raw milk. and livestock.


and major exports are various crops,


Imports and exports were also summarized by land use (Table















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3-5).


Based on data for average production practices, the largest use of phosphorus


was as fertilizer for improved pasture (68


) due to its large geographical extent.


Dairies with 19 percent of the imports accounted for the largest export of phosphorus

(36 %).

Net phosphorus imports were calculated for each land use for comparison on a


unit basis.


These coefficients give a relative assessment of the intensity of phosphorus


use across land use types.


basis.


Truck crops utilized the most phosphorus per acre on a net


Dairies are three times more intensive in the use of phosphorus than improved


beef pasture.


Sod production results in a net export of phosphorus per acre since soil


as well as plant biomass is harvested.


Under the base case scenario, more than 3400


net tons of phosphorus were imported to the north Okeechobee basin annually,


compared to the high phosphorus scenario,


which


resulted in more than 5000 net tons


of phosphorus being imported annually (Table 3-2).

Under the dispersed phosphorus management scenario, changes in sugarcane

and dairy practices had an impact on imports and exports of phosphorus-containing


materials.


Fertilizer was reduced by 71 tons annually from the base case as a result of


substituting rice for corn in rotation with sugarcane.


any phosphorus fertilizer.


Rice production does not require


Changes in annual exports associated with this practice were


also observed: a 51,500 ton increase in rice exports, a 20,000 ton increase in sugarcane

exports due to the rice effect on yield, and a 12,430 ton decrease in sweet corn exports.









Table


. Phosphorus Imports to and Exports from the North Okeechobee Basin


under the Base Case Scenario.


PHOSPHORUS


IMPORT
(tons/yr)


LAND USE


PHOSPHORUS


EXPORT
(tons/yr)


NETP


IMPORTS
(Ibs/unit-yr)


Improved Pasture


2938


Dairy


11 lbs/ac-yr
39 lbs/cow-yr
(33 lbs/ac-yr)
1.9 lbs/ac-yr
16 lbs/ac-yr
-10 lbs/ac-yr


Citrus


Sugarcane
Sod


Truck Crops
Urban Residential
Ornamental
Unimproved Pasture/


lbs/ac-yr


3 lbs/cap-yr
21 lbs/ac-yr


0.03


Waste treatment


Golf Course


Commercial Forest


bs/ac-yr


bs/MGY


24 lbs/ac-yr
-.14 lbs/ac-yr


0
4329


1 ton
1 lb


= 907 kg
= 453.6 2


Rangeland


I









compost exports decreased by 36,000 tons annually.


When all solids were composted


as in design 2, annual exports increased by 230,800 tons over the base case.


effects of these changes on the annual net import of phosphorus to the basin are


summarized in


Tables 3-3 and 3-4


for designs 1 and


respectively.


Reduction in net


imports was achieved by source reduction and export enhancement.

The ratio of the tons of purchased phosphorus imports to phosphorus inputs


from the environment may be referred to as the phosphorus investment ratio.


Using


data from Figures 3-1 through 3-5, this ratio was at its maximum of 8.6 under the


maximum phosphorus use scenario (6050/700).


ratio by 28 percent.


1987


Phosphorus management decreased the


The phosphorus investment ratio was greatest for dairies prior to


. Improved beef pasture, other agriculture, and sugarcane are other land use types


with ratios significantly greater than the basinwide average.

Another ratio useful for comparing scenarios is the net phosphorus ratio, or the


ratio of the tons of phosphorus in products to purchased phosphorus imports.


The net


phosphorus ratio was greatest under the dispersed phosphorus management, design


scenario.


The export of composted dairy manure and rice from sugarcane fields


contributed to the 80 percent increase from 0.15 (935/6050) under the maximum

phosphorus use scenario to 0.27 (1141/4258).

Phosphorus Runoff

Phosphorus concentrations in drainage waters from all land uses were estimated




















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dispersed phosphorus management scenarios, respectively.


with increasing phosphorus concentration.

dairies with concentrations exceeding 0.9 m


The map color intensifies


Comparison with the land use map shows

ig P/I. High concentrations are also


indicative of muck soils south of Lake Istokpoga and in the southern portion of the


135 subbasin.


Lower concentrations in the range of 0.2


- 0.3 mg P/I


are associated


with forested uplands, unimproved pasture, and rangeland.

Figure 3-11 illustrates the spatial heterogeneity of phosphorus runoff


concentration among land use polygons under the base case scenario. More than 6000

polygons had average runoff concentrations averaging less than 2 mg P/I, whereas


only 4 polygons had concentrations exceeding 10 mg P/1.


The hierarchical nature of


this relationship is common to the distribution of chemical elements.

Under the maximum phosphorus use scenario, 20 percent of the annual net

phosphorus inputs entered basin drainage waters as runoff, compared to 17 percent with


base case phosphorus management.


Dairies and beef pasture contributed more than 90


percent of the phosphorus in runoff and at the basin outlet.


Eighty-five percent of the


307 tons of annual dairy runoff phosphorus was attributed to the barn and high intensity

areas under maximum phosphorus use.

Forested uplands and grassy scrubland were estimated to contribute 33 tons of


runoff


phosphorus annually under the redevelopment scenario.


Dairy runoff under the dispersed phosphorus management scenario, design 1




































10,000


~~s~4S
7/ /
+x 4
n/

/
"'R~I'A
~:7/


/ /, <
I; t~jj<;




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i*

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it


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7/
7/


>0-2


> 2-4


>4-6


>6-8


>8-10


> 10


Phosphorus Runoff Concentration (mg/1)


Figure 3-11


Spatial Hierarchy of Runoff Concentration among Land Use Polygons.


3.000


/5^y^









resulted in a 46 percent reduction in dairy runoff (31.9 tons) when compared to the


base case scenario. Runoff concentrations from dairy land uses still exceeded 0.9 mg

P/1 under both designs. Since the milk herd is restricted from pasture when housed in


confinement systems, runoff from these fields returned to background levels.

The difference between phosphorus inputs and phosphorus runoff represents


onsite phosphorus storage.


Under redevelopment conditions, an estimated 297 tons of


phosphorus were stored onsite in the watershed annually.


More than an order of


magnitude increase in annual onsite storage (4634 tons P) was observed by 1987


most


of which was associated with improved beef pasture.

Phosphorus Outflow

Basin phosphorus outflow from each polygon was calculated as the difference


between runoff phosphorus and assimilated phosphorus.


Figure 3-12 is a map showing


per unit basin outflow from each polygon under the base case scenario.


sources, the units are acres.


For nonpoint


Units are cows for dairies which have both point and


nonpoint source characteristics, and million gallons for the point source sewage


treatment plant.


Basins with the smallest assimilation coefficients, such as S-191,


154, and C-41, show the greatest per unit outflow from the basin as represented by the

darker coloration.

Under the base case, more than half of the estimated 228 tons of basin


phosphorus outflow annually was attributed to improved beef pasture.


Dairies


















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