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Investigation of Hydric and Sub-aqueous Soil Morphologies to Determine Florida Sandhill Lake Stage Fluctuations

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Title:
Investigation of Hydric and Sub-aqueous Soil Morphologies to Determine Florida Sandhill Lake Stage Fluctuations
Copyright Date:
2008

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Aquifers ( jstor )
Groundwater ( jstor )
Hydrology ( jstor )
Lakes ( jstor )
Minerals ( jstor )
Sloping terrain ( jstor )
Soil morphology ( jstor )
Soils ( jstor )
Topographical elevation ( jstor )
Water tables ( jstor )
St. Johns River, FL ( local )

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University of Florida
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University of Florida
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Copyright the author. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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5/4/2002
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52200563 ( OCLC )

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INVESTIGATION OF HYDRIC AND SUB-AQUEOUS SOIL MORPHOLOGIES TO DETERMINE FLORIDA SANDHILL LAKE STAGE FLUCTUATIONS By LARRY R. ELLIS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2002

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Copyright 2002 by Larry R. Ellis

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iii ACKNOWLEDGMENTS This research was funded by the St. Johns River Water Management District. I would like to thank supervisory committee chai r Dr. Mary E. Collins, for her invaluable guidance. I thank my committee members, Wade Hurt and Dr. Daniel Spangler for their contributions to my research. The combin ation of each person’s view of pedology and hydrology provided me with a uniqu e perspective on Florida soils. I would also like to thank a ll of my friends at the Univ ersity of Florida. Their companionship and advice were always there when I needed it. I thank my family. They have provided me support and guidance through out life. Finally, I would like to thank my fianc. I would not be where I am toda y without her many years by my side. I am truly blessed to have so many good people surround me.

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iv TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................. iii LIST OF TABLES............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii ABSTRACT....................................................................................................................... xi INTRODUCTION ...............................................................................................................1 The Need for Water Management in Florida.................................................................. 1 Florida Water Management Districts.............................................................................. 2 Research Goals and Objectives....................................................................................... 4 MINIMUM FLOWS AND LEVELS ..................................................................................5 Legislation.................................................................................................................... ... 5 Multiple Lake Levels Approach ..................................................................................... 5 Lake-Level Definitions ............................................................................................ 6 Problems Associated With Water Level Data.......................................................... 7 Priority Surface Water Bodies ................................................................................. 8 SJRWMD MFL Methods: Establishing MFLs for a Lake............................................ 11 Determination of Current Hydrologic Regime ...................................................... 11 Problems Associated With the Determination of the Current Hydrologic Regime11 Predicting Minimum Lake Levels.......................................................................... 13 MFL Validation and Implementation..................................................................... 13 A New Direction for Minimum Flow s and Levels Research: Soils ............................. 14 Hydric and Sub-Aqueous Soils.............................................................................. 14 The Need for Soil Investigations............................................................................ 15 Sandhill Lakes for Initial Soils Study .................................................................... 15 DESCRIPTION OF THE STUDY AREA ........................................................................17 Regional Setting............................................................................................................ 19 Physiography.......................................................................................................... 19 Climate................................................................................................................... 23 Hydrogeology ............................................................................................................... 25 Ocala Limestone..................................................................................................... 28

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v Hawthorn Group .................................................................................................... 29 Pleistocene Terrace Deposits a nd other Coarse Clastics........................................ 30 Upper Etonia Creek Basin Chain of Lakes ............................................................ 30 Soils.......................................................................................................................... ..... 32 Soils of Clay County.............................................................................................. 33 Soils Near Sand Hill Lake...................................................................................... 37 Soils Near Lake Magnolia...................................................................................... 37 METHODS ........................................................................................................................ 42 Objective 1 – Investigate Soil and Hydrol ogy of Sand Hill Lake and Lake Magnolia 42 Scale of Study ........................................................................................................ 42 Transect Location................................................................................................... 42 Construction, Installation, and Eleva tions of Wells Along Transects ................... 45 Groundwater Hydrology: Surficial Aquifer Monitoring........................................ 47 Surface Wa ter Hydrology: Stage Fluctuations....................................................... 47 Objective 2 – Develop soil-base d lake stage indicators................................................ 48 Initial Morphology Investigations.......................................................................... 49 Detailed Morphology Investigations...................................................................... 49 Establishing a Soil-Based Lake Stage Indicator .................................................... 53 RESULTS AND DISCUSSION........................................................................................54 Objective 1 – Soil and Hydrologic Investigation of Study Lakes ................................ 54 Lake Scale Groundwater Hydrology...................................................................... 54 Lake-Scale Surface Water Hydrology ................................................................... 58 Objective 2 – Develop soil-base d lake stage indicators................................................ 63 Initial Soil Morphology Investigation.................................................................... 63 Detailed Soil Morphological Investiga tion of Transect 1 on Sand Hill Lake........ 69 Detailed Soil Morphology Investigation of Transect 5 on Sand Hill Lake............ 75 Soil Morphology Investiga tion – An Overview..................................................... 80 Soil-Based Lake-Stage Indica tors For Sand Hill Lake .......................................... 89 Soil-Based Lake Stage Indicat ors for Lake Magnolia ........................................... 91 Soil-Based Lake Stage Indi cators for Both Lakes ................................................. 91 CONCLUSIONS................................................................................................................94 APPENDIX LAKE STAGE STATISTICS............................................................................................98 LITERATURE CITED....................................................................................................102 BIOGRAPHICAL SKETCH ...........................................................................................104

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vi LIST OF TABLES Table page 1. Geologic formations and hydrologic units of the Lake Brooklyn area......................26 2. Lake-stage statistics based on La ke Magnolia interpolated stage data......................60 3. Lake stage statistics based on Sa nd Hill Lake interpolated stage data ......................62 4. Elevation features occurring ne ar Transect 1 on Sand Hill Lake. .............................90 5. Elevation features occurring ne ar Transect 5 on Sand Hill Lake. .............................91 6. Proposed soil-based lake stage indicato rs for Lake Magnolia and Sand Hill Lake...92 A-1. Lake stage statisitics calculated for Sand Hill Lake. .................................................98 A-2. Lake stage statisitics cal culated for Lake Magnolia. .................................................100

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vii LIST OF FIGURES Figure page 1. The Five Water Manageme nt Districts of Florida.....................................................3 2. Hypothetical current (blue) and mini mum (red) hydrologic regimes for a surface water body..................................................................................................................7 3. Hydrographs for a chain of sandhill la kes in the Upper Etonia Creek Basin ............9 4. Satellite imagery from 1992 and 1996 showing lake surface area changes ..............10 5. Panoramic view of study lakes ..................................................................................17 6. Location of the study lakes ........................................................................................18 7. Upper Etonia Creek drainage basin ...........................................................................20 8. Physiographic regions of the study area. ...................................................................21 9. Surface elevation of Clay County..............................................................................22 10. Locations of precipitation stations near the study area..............................................23 11. Rainfall contours showing the annual normal rainfall calculated by the SJRWMD.24 12. Geologic cross section of Alac hua, Bradford, and Clay Counties.............................27 13. Potentiometric surface of the Floridan Aquifer .........................................................29 14. Drainage sequence of the Upper Etonia Creek Basin chain of lakes.........................31 15. Perspective view of the chain of la kes from Blue Pond to Halfmoon Lake..............32 16. Geographic distribution of Soil Orders in Clay County. ...........................................34 17. Estimated depth to the surficial a quifer (water table) for Clay County.....................35 18. Geographic distribution of hydric soils in Clay County............................................36 19. Geographic distribution of Soil Orders near Sand Hill Lake.....................................38

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viii 20. Geographic distribution of soils near Sand Hill Lake................................................39 21. Geographic distribution of So il Orders near Lake Magnolia.....................................40 22. Geographic distribution of soils near Lake Magnolia................................................41 23. Transect locations on Lake Magnolia and Sand Hill Lake........................................43 24. Transect slope characteristics on Lake Magnolia and Sand Hill Lake......................43 25. Flow-through slope diagram showing water table and direction of flow. .................44 26. Seepage slope diagram showing wa ter table and direction of flow...........................44 27. Monitoring well diagram. ..........................................................................................45 28. Transect diagram showing points where elevations were recorded...........................46 29. Surveying the location of monitoring wells on Transect 1 (Sand Hill Lake)............46 30. Available stage records for Lake Magnolia and Sand Hill Lake...............................48 31. Block diagram showing the layout of the trench used for detailed soil morphology investigations. ............................................................................................................50 32. Surveying an undisturbed area near Tran sect 1 to locate the FH, AVE, and FL elevations (Sand Hill Lake) .......................................................................................51 33. Trench in an undisturbed area ne ar Transect 1 (Sand Hill Lake). .............................51 34. Exposed lake bottom resulting from low lake levels (Sand Hill Lake).....................52 35. Exposed lake bottom resulting from low lake levels (Lake Magnolia).....................52 36. Sand Hill Lake stage fluctuations occurring during the study...................................54 37. Hydrologic cross-section for Transect 1 on Sand Hill Lake......................................55 38. Hydrologic cross-section for Transect 2 on Sand Hill Lake......................................56 39. Hydrologic cross-section for Transect 3 on Sand Hill Lake......................................56 40. Hydrologic cross-section for Transect 4 on Sand Hill Lake......................................57 41. Hydrologic cross-section for Transect 5 on Sand Hill Lake......................................57 42. Stage record frequency for Lake Magnolia. ..............................................................58 43. Interpolated stage record for Lake Magnolia.............................................................59

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ix 44. Stage duration curve for Lake Magnolia ...................................................................60 45. Stage record count for Sand Hill Lake .......................................................................61 46. Interpolated stage record for Sand Hill Lake.............................................................62 47. Stage duration curve for Sand Hill Lake....................................................................63 48. Typical stratified mineral layers ................................................................................65 49. Soils sampled from the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations near Transect 3 (Sand Hill Lake) .....................................................65 50. Dominant wind direction of Sand Hill Lake..............................................................66 51. Histosols occurring near on the seepage slopes of Sand Hill Lake ...........................67 52. Inceptisol with a Histic epipedon occu rring near Transect 2 on (Lake Magnolia)....68 53. Transects chosen for detailed study at Sand Hill Lake and Lake Magnolia..............69 54. Trench near Transect 1 exposing the soil morphology at the Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake).......................................70 55. Epipedon near the Frequent High (FH) level showing both stratified hemic and stratified mineral layers (located on Sand Hill Lake Transect 1). .............................71 56. Epipedon showing the maximum number of mineral stratified layers (located on Sand Hill Lake Transect 1).. ......................................................................................72 57. Epipedon showing the 20% of the maximu m number of stratified mineral layers (located on Sand Hill La ke Transect 1).. ...................................................................72 58. Epipedon showing diffuse stratified la yers occurring below the Frequent Low (located on Sand Hill La ke Transect 1). ....................................................................73 59. Trench near Transect 1 exposing the soil morphology at the Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake).......................................74 60. Trench near Transect 5 exposing the soil morphology at the Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake).......................................76 61. Epipedon near the Frequent High (FH) level showing both stratified hemic and stratified mineral layers (located on San Hill Lake Transect 5). ...............................77 62. Epipedon showing the maximum number of mineral stratified layers (located on Sand Hill Lake Transect 5).. ......................................................................................77

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x 63. Epipedon showing the 20% of the maximu m number of stratified mineral layers (located on Sand Hill La ke Transect 5).. ...................................................................78 64. Trench near Transect 5 exposing the soil morphology at the Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake).......................................79 65. Trench showing soil morphology across th e Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations of Transect 1 (Sand Hill Lake)...........................82 66. Trench showing soil morphology across th e Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations of Transect 5 ( Sand Hill Lake)..........................83 67. Trench across the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations of Transect 1 (Lake Magnolia). ................................................................84 68. Typical hemic layer occurring above th e Frequent High of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. .....................................................................85 69. Typical stratified hemic layers occurri ng at the Frequent Hi gh of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. ..........................................................86 70. Typical stratified mineral layers occurring at the Average and Frequent Low of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. ...............................87 71. Typical diffuse stratified hemic layers occurring below the Frequent Low of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. .....................................88 72. Stage/Duration Curve for Sand Hill Lake..................................................................93 73. Sage/Duration Curve for Lake Magnolia...................................................................93

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xi Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INVESTIGATION OF HYDRI C AND SUB-AQUEOUS SOIL MORPHOLOGIES TO DETERMINE FLORIDA SANDHILL LAKE STAGE FLUCTUATIONS By Larry R. Ellis May 2002 Chair: Mary E. Collins Department: Soil and Water Science In an effort to protect FloridaÂ’s water resources from significant harm, the five water management districts have been le gislatively mandated to establish Minimum Flows and Levels (MFLs) on their lakes, rive rs, springs, and aquifers . To describe the fluctuating hydrology of their lakes, the St . Johns River Water Management District (SJRWMD) has defined the Fr equent High (FH), Average (AVE), and Frequent Low (FL) levels as the lakeshor e elevations that are flooded 20%, 50%, and 80% of the time respectively. The SJRWMD uses Lake Stage Indicators (LSIs) to determine the historic FH, AVE, and FL of lakes that have weak stage records. Currently the SJRWMD relies heavily on vegetation-based LSIs To date, no soil-based LSIs have been developed due to the lack of knowledge concerning the relationships between hydric/s ub-aqueous soil morphology and lake stage fluctuations. This research investigated th ese relationships for two sandhill lakes in the SJRWMD. Lake Magnolia and Sand Hill Lake were chosen because of their small stage

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xii fluctuations and undisturbed soils. Histos ols occurred on the seepage slopes while Entisols occurred on the non-seepage slopes. The sub-aqueous soils on the non-seepage slopes of both lakes had stratifie d layers in the epipedon. The stratified layers varied in number, thickness, contrast, and composition as a function of lake stage fluctuations. These variations occurred at consistent elevations on Sand Hill Lake, allowing for the development of three soil-based LSIs. Results from soil and hydrologic monitoring provided a better understanding of the lake sÂ’ hydrology and soil morphology. Based on these results it was recommended that the prel iminary soil-based LSIs be used as a starting point for soil-based LSIs on all SJRWMD lakes.

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1 INTRODUCTION The Need for Water Management in Florida Florida is famous for its water res ources. With approximately 1200 km of beaches, 7800 lakes, and 320 springs, Florida attracts over 50 million tourists each year, making it the fourth most populated state in the United States. Tourism accounts for more than 40 billion dollars of Flor idaÂ’s economy while employing hundreds of thousands of Floridians (Data Source: http://www.flausa-media.com ). State legislators are faced with the difficult task of providing water for 15 million residents while protecting the water resources fr om over consumption so that its largest industry, tourism, continues to thrive. FloridaÂ’s water resources ex ist due to a small surplus of rain water. Annually, Florida receives 1300 mm of rain, but endur es 1100 mm of evapotranspiration. The surplus, 200 mm/yr, is what the lakes, rive rs, and aquifers rely on for recharge. As FloridaÂ’s population grows, so does the demand for water. Managing water use is not as simple as calculating the statewide surplus to determine available water. The demand for water is high, regardless of rainfall conditions. Water in Fl orida is stored not only as surface water but as groundwater in a complex system of aquifers often connected with surface water bodies. The availability of water is a function of the hydrogeology, climate, and the demands humans place on water. Water may not always be available where demand is highest. Since supply and demand do not always coincide geographically or temporally, many areas of Fl orida experience frequent water shortages.

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2 To cope with these supply and demand problem s, five Water Management Districts have been established in Florida. Florida Water Management Districts Striking a balance between pr otecting water resources for future use, and providing water for current use, has been the task of the Florida Water Management Districts (WMDs) for the past thirty years (Figure 1) . These five agencies have the power to manage water resources through taxation, permitti ng, etc. Backed by state legislature, the WMDs manage water based on current laws a nd scientific knowledge , but also evolve their policies as the laws and knowledge change s. A recent change that has taken place in the early 1990’s was the establishment of the Minimum Flows and Levels (MFLs) Program. In 1994, Florida’s legislation mandated that all five WMDs establish MFLs for all the surface water and groundwater in Florid a (F.S. 373.042). These MFLs are meant to protect Florida’s water resources from “significant harm.” The goal is that the maximum allowable water demands will be defined for all areas of the state, thus facilitating judicial use of the water now and in the future.

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3 1000100200Kilometers NWFWMDS R W M DS J R W M DSFWMDS W F W M DGulf of MexicoAtlantic Ocean Figure 1. The Five Water Management Distri cts of Florida: Northwest Florida Water Management District (NWF WMD), Suwannee River Wate r Management District (SRWMD), St. Johns River Water Management District (SJRWMD) , Southwest Florida Water Management District (SWFWMD), S outh Florida Water Management District (SFWMD). A crucial part of the MFL methods is to identify the current h ydrologic regime of the lakes, rivers, and aquifers that are to be protected. Determining what the high, average, and low water levels are for a part icular water body can prove difficult if long term stage records are not available. In these cases, the WMDs must use physical evidence of water fluctuations such as wa ter marks on trees and boat docks as well as biological evidence such as vegetation co mmunity distribution. Unfortunately, the

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4 evidence found by the WMDs often does not provide the precision or the accuracy needed to determine the exis ting hydrologic regime. Water marks can fade. Vegetation communities can migrate, be disturbed, or have boundaries that are not easily delineated. A more precise and accurate me thod of identifying current hydrologic regimes is needed. Soils can provide that accuracy and pr ecision. The morphology of the hydric and sub-aqueous soils that surround la kes and rivers are subject to frequent flooding. If the relationship between surface water fluctuat ions and soil morphology can be understood, then soil morphology can be used to determ ine the stage fluctuations of areas where hydrology data is insufficient. Research Goals and Objectives The goal of this research is to determine what, if any, features in the soil can be used to determine the current hydrologic regime of SJRWMD sandhill lakes. To accomplish this goal, two research ob jectives have been established. 1. To investigate soil and hydr ology of selected study lakes 2. To develop soil-based lake stage indicators

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5 MINIMUM FLOWS AND LEVELS Legislation Florida Legislature mandates the WMDs pr otect water resources from significant harm by establishing MFLs (Chapter 373.042 F. S.) The legislature defined MFLs as water flows and levels that represent the lo wer threshold of what a water-based system can tolerate. Levels below this threshold will cause “significant harm” to the system. Florida Administrative Code (62-40.473) broadly outlines protection by stating, “consideration shall be given to the prot ection of water resour ces, natural seasonal fluctuations in water flows or levels, and environmental values associated with coastal, estuarine, aquatic, and wetland s ecology.” Specifically, the code identifies the following areas for protection: recreation in and on the wa ter, fish and wildlife habitats, the passage of fish, estuarine resources, transfer of detritus material, maintenance of freshwater storage and supply, aesthetic a nd scenic attributes, filtrati on and adsorption of nutrients and other pollutants, sediment loads, water quality, and navigation. Further consideration of protection from significant harm is left to the water management districts’ discretion (Hupalo et al., 1994). Multiple Lake Levels Approach The long-term fluctuations of a wa ter body, called the hydrologic regime, are driven by the water body’s constantly fluc tuating hydrologic inputs and outputs. To approximate a hydrologic regime, the SJRWMD uses a multiple level approach. The levels used are the Infrequent High (IFH), Frequent High (FH), Average (AVE), Frequent

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6 Low (FL), and Infrequent Low (IFL). (St. Johns River Water Manageme nt District Staff, 1994). Lake-Level Definitions The IFH level is defined by the 10% flood ev ent. For surface water, that is the elevation that experiences flooding from surface water 10% of the time. The FH, AVE, FL, and IFL are represented by the 20%, 50% , 80%, and 90% flood events, respectively. Levels can be determined by calculating th e 10th, 20th, 50th, 80th, a nd 90th percentiles of a water level data (Rao, 1982). MFLs are used to describe the mi nimum hydrology below which “significant harm” may occur: Minimum Frequent High (M-FH), Mini mum Average (M-AVE), and Minimum Frequent Low (M-FL) which de scribed the 20%, 50%, and 80% flooding events of the minimum hydr ologic regime (Figure 2).

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7 TimeLake Stage FH AVE FL M-FH M-AVE M-FL Figure 2. Hypothetical current (blue) and minimum (red) hydrologic regimes for a surface water body. Solid line re presents the hydrologic regime and the dotted lines represent the lake levels that approximate those regimes. Frequent High (FH) and Minimum Frequent High (M-FH) = 20% exceedence. Average (AVE) and Minimum Average (M-AVE) = 50% exceedence. Freque nt Low (FL) and Minimum Frequent Low (M-FL) = 80% exceedence. Problems Associated With Water Level Data How closely the calculated water levels match the actual water levels, depends on the quality of the data. A da ta set that spans an entire hydrologic regime, with records that are frequent enough to show most of th e fluctuations, will al low calculated levels that are very close to the actual levels. However, a data set that is either sparsely populated or short in duration will likely not yi eld useful levels. For surface water, the quality of this data can vary. Some lakes a nd rivers have staff gauges near boat docks or

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8 other places that facilitate data collection. Other surface waters can be in remote or private areas that hi nder data collection. Priority Surface Water Bodies Some of these surface waters, although remote, are on the SJRWMD’s list of priority surface water (St. Johns River Water Management District Staff, 1994). The prioritization process has evolve d since the 1980’s. Priority la ke list criteria have been added, and therefore so have la kes. Specific criteria have changed over the years, but basically, priority surface wate rs are those that are currently threatened by pumping, are currently low for other reasons, or are projec ted to be drastically low by 2010 (St. Johns River Water Management District Staff, 1994) . Additionally, citizen complaints often coincide with these factors and can have a lake listed. Priority lakes are ones that for one reason or another, are thought to be in danger of being too lo w either currently or in the near future. Many sandhill lakes are priority lakes. Th ese lakes can have excellent hydraulic communication with the Floridan aquifer via si nkholes and other karst features. As the potentiometric head in the Fl oridan aquifer fluctuates, so do the sandhill lake levels. Lake Brooklyn is an example of this. Seismi c studies have shown Lake Brooklyn to have “collapse features that show fractures a nd faulting in the Hawthorn Group” (St. Johns River Water Management District Staff, 1992). Lakes that have this hydraulic communication with the Floridan Aquifer, such as Lake Brooklyn, can have large stage fluctuations (Figure 3) resulting in dr astic surface area changes (Figure 4).

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9 Figure 3. Hydrographs for a chain of sandhill lakes in the Upper Etonia Creek Basin. Units for lake stage are in feet above Sea Le vel. Lake Lowry is also know as Sand Hill Lake. Note the large stage fluctuations of Lake Brooklyn compared to Lake Lowry (Source: Merritt, 2001).

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10 Figure 4. Satellite imagery from 1992 and 1996 s howing lake surface area changes. Note the large surface area change of Lake Br ooklyn compared to the small surface area change of Sand Hill Lake. Lake Brooklyn is a priority lake due to its large stage and surface area fluctuations. S S a a n n d d H H i i l l l l L L a a k k e e Lake Brooklyn Lake Brooklyn 1 1 9 9 9 9 2 2 1 1 9 9 9 9 6 6 S S a a n n d d H H i i l l l l L L a a k k e e

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11 SJRWMD MFL Methods: Establishing MFLs for a Lake Determination of Current Hydrologic Regime The first step in establishing MFLs for a la ke is to describe the current hydrologic regime by determining the current lake levels . The SJRWMD may identify all five water levels, but currently only uses three in the MF L process: the FH, AVE, and FL (St. Johns River Water Management District, 1994). Often, the quality of the stag e records is poor. Either th e period of record is too short or the period between r ecords is too long. In either case, the stage records and subsequent statistics usually fail to describe the hydrology. As mandated by the legislation, all WMDs must use the “best available knowledge” (Chapter 373.042 F.S.) In the absence of quality stage data, the “b est available knowledge” for the SJRWMD is usually based on field observations of vegetation. Vegetation can yield valuable inform ation if the SJRWMD understands the physical and biological effects of lake stage fluctuations. Knowing how plant species and communities tolerate various hydrologic regimes, the SJRWMD then develops LSIs. By identifying location and elevation of thes e LSIs, the SJRWMD can approximate the current lake levels. Problems Associated With the Determin ation of the Current Hydrologic Regime In many cases vegetative LSIs do not provide the accuracy or precision needed to identify the FH, AVE, and FL. Precision error results when the horizontal error associated with identifying an LSI translates in to a large vertical error. For example, if the edge of a particular ve getation community typically found on 2% slopes is a FH LSI, and if the identification of that edge result s in a 3 m horizontal error, the subsequent vertical error is 21 cm. For a lake with st age fluctuations of only a few meters, the FH-

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12 FL range may only be 20 30 cm. In this example, the LSI does not precisely identify the FH, AVE, or FL. Since the SRJWMD accepts a 10% exceedence range for their levels, the precision of a LSI must be less than 10% exceedence. Even if the edge of that vegetation comm unity could have been identified with excellent horizontal and verti cal precision, the use of that LSI may be questionable. If that LSI was developed from a poor understanding of the vegetation and surface hydrology relationships, then itÂ’s possible the LSI does not id entify the lake stage it was designed to identify. For example, vegetati on communities that favor seepage slopes are supported by the perched water-table of t hose slopes. The elevations of these communities may be meters above the lake and, therefore, should not be used as LSIs. Use of these communities would result in identification of a set of levels that are higher than those of the current hydrology. The two previous examples demonstrated how the use of vegetation can result in poor accuracy and precision due to the mi sinterpretation of vegetation/hydrology relationships, as well as the difficulties in de termining the exact elevation of a vegetation feature. The MFL process could benefit from LSIs that are either more precise or more accurate than vegetation-based LSIs. Thus, research was being conducted to develop soil-based LSIs. The inclusion of soil-based LSIs could provide much needed assistance to the SJRWMD scientists. Currently, there is ve ry little known about the relationship between the hydrology and the morphology of the so ils that surround many of the SJRWMD lakes. Sandhill lakes are a very common type of lake in the SJRWMD. Their soils are generally sandy, with little bu ild up of organic matter and few redoximorphic features.

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13 Although some hydric soil indicators are comm on to these areas, there have been no investigations in to use the soil features to help determine the current hydrologic regime. Currently, the SJRWMD ha s no soil-based LSIs. Predicting Minimum Lake Levels Once the current lake levels have been de termined for a particular lake from “best available knowledge,” the SJRW MD must decide how much lower the lake levels can drop without causing “significant harm” (Chapt er 373.042 F.S.). The loss of watercourse navigability, significant retreat of existing wetland communities, and the oxidation of hydric soils are some of th e “harms” that the Florida Administrative Code (62-40.473) deems “significant.” The lowest allowable le vels, or MFLs, should pr otect the lake from these harms. In the case of lakes that are currently very low, the MFLs may be above the current lake levels. MFL Validation and Implementation Once MFLs have been initially determined for a lake, hydrologic models are used to determine what effect the MFLs will have on other groundwater and surface water levels. The SJRWMD considers current and future demands for consumptive water use in order to determine when MFLs will be violated. Once a set of MFLs are initially determined, they must be included in hydrol ogic models to predic t whether the proposed MFLs will cause “significant harm.” (Kinser and Minno, 1995). After the MFLs have been tested in this manner, they must be approved by the governing board to be used for future permitting decisions. Priority lakes are currently the focus of the SJRWMD MFL Program. Since many of these lakes are a priority because of ex tremely low lake levels, the MFLs currently

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14 being determined are often in violation. In these cases, an emergency recovery strategy is set in place to bring the lake levels back to MFLs. Priority lakes have been identified as pr oblematic or sensitive to pumping effects. Therefore, MFLs on these lakes will often cause permits to be restricted or denied. This will cause people to challenge the MFLs in court. Therefore, a solid foundation of research applied to lakes in the SJRWMD is necessary for the SJRWMD to defend the MFLs it sets. A New Direction for Minimum Fl ows and Levels Research: Soils To use soils as indicators of lake-stage fluctuations, the relationship between the morphology and the hydrology of a particular lake must be understood. The SJRWMD has recently begun research to furthe r the understanding of soil and hydrology relationships. The starting point for this research was hydric and sub-aqueous soils. Hydric and Sub-Aqueous Soils A hydric soil is defined as “a soil that formed under conditions of saturation, flooding or ponding long enough during the gr owing season to develop anaerobic conditions in the upper part” (Federal Regist er, 1994). While the hydric soils definition does not impose any restrictions as to the maximum amount of flooding a soil can experience, a widely accepted definition of soil does. The definition of soil in Soil Taxonomy did not include shallow water sediment s as soils (Soil Survey Staff, 1975). The revised edition of Keys to Soil Taxonomy states a new definition of soil (Soil Survey Staff, 1998). Research (Demas and Rabe nhorst, 1999) showed that shallow water sediments experienced pedogenesis as the resu lt of four pedogenic processes: additions, removals, translocations, and transformations. This research proposed a new category of soils be included in the definition of soil: s ub-aqueous soils. A major change in the

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15 definition of soil followed by re-defining the ho rizontal limit of soil used to distinguish between soils and sediments. The horizontal limit of soil is now defined as areas where “the surface is permanently covered by water too deep (typ ically greater than 2.5m) for the growth of rooted plants,” (Soil Survey Staff, 1999). The hydric soils definition and revised soil definition signifi es a forward thinking regard ing sub-aqueous soils. Soil forming processes that take place in flooded soils are now recognized with these definitions. The Need for Soil Investigations Several questions arise when hydric so ils are used to determine specific fluctuations in hydrology: What does the presence of a hydr ic soil say about the flooding? Does the presence of a hydric soil guarantee a particular flooding event? What about hydric soils o ccurring on seep slopes? How do their elevations relate to the various flooding events? Questions such as these can be answered th rough research that is applied to hydric and sub-aqueous soils and their relationshi ps with hydrology. Since priority lakes currently need the attention of the SJRW MD, the soils surroundi ng these lakes are a logical place to focus their research efforts. Sandhill Lakes for Initial Soils Study By virtue of their sometimes large and e rratic lake-stage fluctuations, many of the priority lakes in the SJRWMD are sandhill la kes. The SJRWMD has identified the need to investigate soil and hydr ology relationships for prior ity lakes and, has therefore chosen, sandhill lakes as the initial type of lake to be studied. Resulting from that

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16 decision, this research may provide the insigh t needed to interpret the soil morphologies of these priority lakes and other sandhill lakes.

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17 DESCRIPTION OF THE STUDY AREA Two lakes were chosen for study: Sand Hill Lake (Figure 5A) and Lake Magnolia (Figure 5B). The center of Lake Magnolia is 29o40’50” N, 82o01’00”W. The center of Sand Hill Lake is 29o50’40”N, 82o00’00”W. Both lakes are located in the southern tip of the Camp Blanding U.S. Army Ba se, Clay County, Florida (Figure 6). A B Figure 5. Panoramic view of study lakes. Sand Hill Lake looking north (A) and Lake Magnolia looking north-east (B). Note the white sands and lo w stage of both lakes. A drought lowered both lakes and exposed their sub-aqueous soils.

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18 Camp BlandingSurface Water Wetlands Uplands N E W S 202Kilometers Figure 6. Location of the study lakes: Lake Ma gnolia and Sand Hill Lake in Clay County, Fl. The locations of Kingsley Lake a nd Blue Pond are shown for reference. Kingsley Lake Sand Hill Lake Lake Magnolia Blue Pond Camp Blanding U.S. Army Base

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19 Regional Setting Physiography The study lakes lie in the northern por tion Upper Etonia Creek Basin (UECB). The UECB is located in North-Ce ntral Florida and spans a 445 km2 in area that includes parts of Alachua, Bradford, Clay, and Putnam Counties (Figure 7). In the southwestern part of Clay County, or the northeastern part of the UECB, surface elevations range from 60 m to 30 m National Geodetic Vertical Datum (NGVD) (Motz and Heaney, 1991). This southwestern portion of Clay County is located in the Interlachen Sand Hills physiographic region, which is ju st south of the Trail Ridg e physiographic region (Figure 8). These two regions lie in the extreme we stern portion of Clay County and are higher in elevation than the surrounding areas. In addition to being t opographic high points of the county, these regions have many small la kes and few streams. Some surface water flow is present in the form of chains of la kes. The rest of Clay County is lower in elevation and has many streams and very few lakes (Figure 9). These streams drain to the eastern boundary of Clay Count y which is the St. Johns River.

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20 Figure 7. Upper Etonia Creek drainage ba sin (Source: Motz and Heaney, 1991)

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21 Interlachen Sand Hills Trail Ridge 505Kilometers 1000100Kilometers Trail Ridge Interlachen Sand HillsSand Hill G e n e v a Figure 8. Physiographic regions of the study ar ea: Trail Ridge and Interlachen Sand Hills. Other physiographic regi ons are shaded gray.

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22 10010Kilometers N E W S USGS 250K DEM0 8 Meters 9 17 Meters 18 26 Meters 27 35 Meters 36 44 Meters 45 53 Meters 54 62 Meters 63 71 Meters 72 80 Meters 81 89 Meters 90 97 Meters 98 106 Meters 107 114 Meters No Data Water Figure 9. Surface elevation of Clay C ounty (Data Source: USGS 1:250,000 Digital Elevation Model) Sand Hill Lake Lake Magnolia St. Johns River

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23 Climate The study area lies in a humid subtropi cal climate (Yobbie and Chappell, 1979). The soil temperature regime is thermic (Weatherspoon et al. 1986). The closest precipitation stations with l ong term rainfall records were located in the cities of Gainesville, Starke, and Palatka, Fl. (Figure 10). Based on these and other precipitation stations located in their district, the SR JWMD calculated rainfall contours. Based on these contours, the annual normal rainfa ll for the study area is around 1350 mm/year (Figure 11). In northeast Flor ida, the wet season generally lasts from June to October. During this time 60 percent of the annual rain fall occurs (Rao et al. 1990). The annual evapotranspiration can range from 10 16 to 1117 mm/yr (Motz and Heaney 1991). Ë Ë ËStarkePalatkaGainesville Rain StationsË N E W S 25025Kilometers Figure 10. Locations of precipitatio n stations near the study area. Sand Hill Lake Precipitation Stations

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24 Figure 11. Rainfall contours showing the a nnual normal rainfall calculated by the SJRWMD. Units are in inches of rain per year (Source: Rao et al., 1990). Study Site

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25 Hydrogeology The surface waters of the UECB area are dom inantly lakes. The lakes occur in depressional areas formed through solution pr ocesses that create sinkholes (Schiffer, 1998). These lakes are part of the surficial aquifer that occurs in the Pleistocene and Miocene Sediments. Generally, the dynamics of this aquifer are directly controlled by the amounts of precipitation and evapotranspi ration, as well as human pumping from the aquifer. Indirectly, the surficial aquifer is influenced by the Floridan aquifer that is confined beneath the surficial aquifer (Tab le 1). The hydraulic pressure differences between the Floridan Aquifer and the surficial aquifer control the rate of recharge to the Floridan Aquifer. Hydraulic pressure differenc es for this area of the state can be as high as 45 m, resulting in as much as 30 cm/yr of recharge to the Florid an Aquifer (Boniol, et al. 1993). Additionally, fluctuations in Fl oridan pressures in combination with fluctuations in surficial aquifer and solu tion processes can foster sinkhole formation. Sinkholes can enhance the hydraulic communica tion between the surf icial and Floridan aquifers which can greatly increase the r echarge of the areas surrounding the sinkholes. All these factors combine to form a comp lex groundwater and surface water hydrology (Figure 12).

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Table 1. Geologic formations and hydrol ogic units of the Lake Brooklyn area. Source: Clark, 1964. Note: The stratagraphic nomenclature used in th is table conforms to the usag e of the Florida Geological Su rvey in 1964. 2 6

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Figure 12. Geologic cross section of Alachua , Bradford, and Clay Counties (Source: Cl ark, 1964). Elevation units are feet abov e Mean Sea Level. Note the elevation diffe rence between the potentiometric surface of the Floridan Aquifer and the “Water Table Aquifer.” High recharge occurs on the Clay/B radford County border. Also note flow in the Floridan is away (east and west) fro m this area. 2 7

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28 Ocala Limestone Clark reported that in the UECB the Flor idan aquifer was confined to the Ocala Group, Avon Park Limestone, Lake City Lime stone, and Oldsmar Limestone formations (Clark, 1963). Today, the Ocal a Group is referred to as the Ocala Limestone and the Lake City Limestone is no longer recognized. The collective thickness of these layers can be greater than 250m. Although the lowest layers are dense and not very permeable, the upper layers are more permeable. The O cala Limestone is the most permeable of these limestone layers. It is highly porous and therefore very pr oductive for groundwater pumping (Clark, 1963). The Floridan aquifer system is present th roughout much of Florida. Water travels from the recharge areas of Florida to the di scharge areas. Generally, the recharge areas are in the center of the stat e, where the highest elevations occur (Boniol et al., 1993). Groundwater flows from the surficial aquife r, through the Hawthorn Layer confining bed, and into the Floridan Aquifer (Figure 12). The areas of recharge will produce the highest potentiometric heads in the Floridan Aquifer. The water in the Floridan Aquifer will flow from these areas of hi gher energy, recharge areas, to areas that lower energy (discharge areas). Some of these discharge areas are springs and other surface waters, but discharge also occurs into the ocean through the sea floor (Schiffer, 1998). Potentiometric maps can be used to show Floridan groundwater in the UECB, flow originates near Lake Brooklyn and flows eas t and northeast towards Lake Magnolia and Sand Hill Lake (Figure 13). This is opposite the direction of flow for the chain of lakes that begins with Blue Pond.

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29 Figure 13. Potentiometric surface of the Floridan Aquifer (Source: Merritt, 2001) modified with flow arrows. The blue arrows represent direction of flow in the Floridan Aquifer. Red arrows show the surface drai nage of a chain of lakes that includes Sand Hill Lake. The orange arrow points to Sand H ill Lake. The center of the blue arrows, 25 km south of Sand Hill Lake, is a major recharge zone. Hawthorn Group The confining bed above the Ocala Limestone is the Hawthorn Group. The Hawthorn Group is a group of Miocene laye rs consisting of sandy clays, clays, Sand Hill Lake

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30 limestones, and dolomites. Most of these layers are phosphatic and are variable in thickness. The more clayey layers are le ss permeable while the more carbonitic layers are more permeable. The lowest part of th e Hawthorn Group is very dense and much less permeable than the rest of the formation (Clark, 1963). Pleistocene Terrace Deposits and other Coarse Clastics Above the Hawthorn Group are two Plei stocene formations and one Miocene formation. The Choctawhatchee Formation is a layer of Miocene age clays and marls with phosophatic nodules and th in layers of limestone. Above this formation are unnamed coarse clastics. These are gravels a nd sands with thin layers of clay. Above these are Pleistocene terrace de posits that consist of main ly unconsolidated sand. The surficial aquifer is a phreatic aquifer present in these laye rs that lie above the Hawthorn Group. Since the Hawthorn Group is confini ng, the base of the surficial aquifer is considered to be the top of the Hawthorn Group. The top of the surficial aquifer is unconfined and commonly referred to as the wa ter table. The water table does fluctuate with time but its average elev ation is a function of surface elevation. Areas of high elevation will have water tables with higher elevations. Areas of low elevation will have low water table elevations (M otz and Heaney, 1992). The av erage saturated thickness of the surficial aquifer surrounding Lake Magnolia and Sand Hill Lake is 18 m (Motz et al., 2001). Upper Etonia Creek Basin Chain of Lakes Sand Hill Lake and Lake Magnolia are part of a chain of lakes that drain from Blue Pond to Halfmoon Lake (Figures 14 and 15) before discharging to Putnam and Goodson Prairies, and ultimately to Etonia Creek. Alt hough drainage occurs through the surficial

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31 aquifer and surface water, the streams are intermittent and may be dry during times of drought (Robison, 1992). Blue Pond Sand Hill Lake Lake Magnolia Lake Brooklyn Lake Geneva Oldfield Pond Halfmoon Lake 202Kilometers Drainage Sequence Figure 14. Drainage sequence of the Uppe r Etonia Creek Basin chain of lakes.

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32 Figure 15. Perspective view of the chain of lakes from Blue Pond to Halfmoon Lake. Soils The morphology of the soil in a given area can reflect many physical and chemical processes occurring in that ar ea. For wet areas, these processes are the chemical reduction of the soil environment resulting in the surface accumulation of organic matter, formation of spodic horizons, and lower chroma soil colors. In th e drier areas, the soil environment is oxidized resulting in higher chroma soil colors. Although organic matter will accumulate on the soil surfac e, the amount will be much less than in the wet areas. Because the water table is lower in the dry areas compared to the wet areas, materials such as clay will be translocat ed to deeper portions of the soil. These major differences in soil morphology can be seen at the Order level of Soil Taxonomy.

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33 Soils of Clay County In Clay County, the soils can be grouped by Order to show differences between the dry southwestern part of the county and the rest of the county which is wet. In the southwestern part of the county, the area su rrounding the study site , Entisols are the dominant upland soil (Figure 16). These so ils are high in quartz sand without much subsurface accumulation of clay or organic matte r within two meters of the soil surface. Patches of Ultisols are present suggesting the En tisols may have clay layers deeper than two meters. Spodosols and Inceptisols ar e located in the wetter ar eas surrounding the lakes. These areas, however, are of minimal extent wh en compared to other areas of the county. Spodosols and Ultisols are dominant throughout th e rest of the county. These areas are lower in elevation and have more streams. The larger number of streams in this part of the county compared to the southwestern part suggests that most of the lower elevations of the county have argillic horizons that are shallow enough and thick enough to support surface runoff in the form of streams. A sh allow groundwater table can also be inferred by the presence of Spodosols thr oughout this part of the c ounty. This inference is confirmed when the estimated water tables fo r each soil map unit are plotted on a map to show the estimated water table de pth for Clay County (Figure 17) Soils in the wettest parts of the county are hydric. A set of hydric soils criteria has been used by the NRCS to identify which soil series have the highe st chance of meeting the hydric soil definition. The soils in the sout hwestern part of Clay County are very well drained and thus dominantly non-hydric. H ydric soils are mapped surrounding the lakes of the southwestern part of the county and extensively throughout th e rest of the county (Figure 18).

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34 10010Kilometers N E W S Soil OrdersAlfisols Entisols Histosols Inceptisols Mollisols Spodosols Ultisols Water Figure16. Geographic distribution of Soil Orders in Clay County. Sand Hill Lake Lake Magnolia St. Johns River

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35 10010Kilometers N E W S Water Table Depth (m)Surface Water 0.00 0.15 0.15 0.30 0.30 0.45 0.45 0.60 0.60 0.75 0.75 1.00 1.00 1.15 1.15 1.30 1.30 1.45 1.45 1.60 1.60 1.75 1.75 2.00 Figure 17. Estimated depth to the surficial aquifer (water table) for Clay County. Sand Hill Lake Lake Magnolia + St. Johns River

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36 10010Kilometers N E W S SoilsNon-hydric Hydric Water Figure 18. Geographic distribution of hydric soils in Clay County. Hydric soils in this figure are soil that meet the Hydric Soils Criteria (Federal Re gister, In Press). Sand Hill Lake Lake Magnolia St. Johns River

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37 Soils Near Sand Hill Lake The soils around the perimeter of Sand Hill Lake are mapped Spodosols. The areas of groundwater seepage on the north shor e of Sand Hill Lake is reflected in more extensively mapped Spodosols (Figure 19). Immediately upland from the Spodosols are mapped Entisols. These soils are well draine d and have deep water tables. Although not reflected in mapping of this scale, these well drained Entisols s hould not be present where groundwater seepage occurs on Sand Hill Lake (Figure 20). Seepage areas are poorly drained and probably have a conf ining layer perching the water table. Soils Near Lake Magnolia The soils around the east perimeter are mappe d Entisols. The west perimeter is mapped Ultisols while Inceptisols and Hist osols are mapped in both the inflow and outflow areas (Figure 21). Most of the series occurring near Sand Hill Lake also occur near Lake Magnolia (Figure 22). As with Sand Hill Lake, the Entisols occur on the nonseepage slopes of Lake Magnolia. These are the eastern slopes. The western slopes as well as the inflow and outflow areas have cl ay horizons that perch the water table.

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38 N E W S 10010KilometersSand Hill Lake SoilsEntisols Inceptisols Spodosols Ultisols Water Figure 19. Geographic distribution of Soil Orders near Sand Hill Lake.

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39 58 34 34 5 34 5 3 34 29 58 10 3 5 58 5 56 5 34 5 37 34 N E W S 10010KilometersSand Hill Lake Figure 20. Geographic distribution of soils near Sand Hill Lake.

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40 N E W S 2000200400MetersLake Magnolia SoilsEntisols Inceptisols Spodosols Ultisols Water Figure 21. Geographic distribution of Soil Orders near Lake Magnolia.

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41 5 3 29 54 34 29 34 37 5 34 10 56 54 N E W S 2000200400MetersLake Magnolia Figure 22. Geographic distribution of soils near Lake Magnolia. SymbolMap Unit 3Hurricane fine sand, 0 to 5 percent slopes 5Penny fine sand, 0 to 5 percent slopes 10Ortega fine sand, 0 to 5 percent slopes 29Rutlege-Osier complex, flooded 34Penny fine sand, 5 to 8 percent slopes 37Ridgewood fine sand, 5 to 8 percent slopes 54Troup sand, 0 to 5 percent slopes 56Kershaw sand, 0 to 8 percent slopes

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42 METHODS Objective 1 – Investigate Soil and Hydr ology of Sand Hill Lake and Lake Magnolia Scale of Study Objective 1 involved investigatio ns at two scales: a regional scale and a lake scale. At the regional scale a literature survey wa s conducted to provide an understanding of the Upper Etonia Creek Watershed. This understa nding helps put in context the hydrology and soils of both Lake Magnolia and Sand Hill Lake. At the lake-scale, a line transect method was employed. Results from the lake -scale study combined with the regional scale study provided the necessary informa tion to describe the hydrology of both study lakes. That information was necessary fo r the correct interpretation of soil morphology needed to accomplish the second objective. Transect Location Based on the findings of the literature review and interpre tations of initial vegetation and soils, five transects were es tablished on Sand Hill Lake and two on Lake Magnolia (Figure 23). Transects were positi oned to represent the non-seepage slopes and seepage slopes (Figure 24). Hydrologic cross-section models for hypothetical seepage and non-seepage slope show the relative placement of the monitoring wells and the difference in water table elevation and flow pattern that exists between the slopes (Figures 25 and 26).

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43 Figure 23. Transect locations on La ke Magnolia and Sand Hill Lake. Figure 24. Transect slope characterist ics on Lake Magnolia and Sand Hill Lake.

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44 Blue arrow indicates direction of water flowW a t e r t a b l eS o i l s u r f a c e Monitoring Well Figure 25. Flow-through slope diagram show ing water table and direction of flow. W a t e r t a b l eS o i l s u r f a c e Blue arrow indicates direction of water flow Monitoring Well Figure 26. Seepage slope diagram showing water table and direction of flow.

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45 Construction, Installa tion, and Elevations of Wells Along Transects Monitoring wells were installed along each transect. Wells were constructed of 6.4 cm OD PCV pipe. Screened areas allowed for the flux of groundwater in and out of the well while bentonite clay provided a seal to protect the wells from short-circuiting during rain. Clean-washed, coarse-grained sa nd was used as back-fill material. (Figure 27). Additional ground elevations were surv eyed every 4 – 5 m except where abrupt changes in topography occurred. At these ab rupt changes, additional elevations were recorded to describe the topography (Figur e 28). All pipe elevations and ground elevations at the pipes were surv eyed (Figure 29) to 0.9 cm precision. Groundwater Groundwater Soil surface Soil surfaceClean Clean washed, washed, coarse coarse grained grained sand sand Bentonite Bentonite grout grout Screened Screened pipe pipe Drain Drain Cap Cap Pipe casing Pipe casing Water flow Water flow Water flow Water flow Soil cap Soil cap Pipe elevation Pipe elevation Ground Ground elevation elevation Figure 27. Monitoring well diagram.

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46 Black arrows show surveyed elevations Red arrows indicate the elevations of the wells were surveyedW a t e r t a b l eS o i l s u r f a c e Figure 28. Transect diagram showing point s where elevations were recorded. Figure 29. Surveying the location of monitori ng wells on Transect 1 (Sand Hill Lake). M M o o n n i i t t o o r r i i n n g g W W e e l l l l s s

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47 Groundwater Hydrology: Surf icial Aquifer Monitoring Once the transects were constructed, weekly monitoring of the wells began. Water levels in the wells were measured with a hand held water meter. Weekly readings of the wells continued for the duration of the one-year research. The data was used to construct a groundwater cross-section of each slope, revealing information of the soil environment, and the response of the water tabl e to lake-stage fluctuations. Surface Water Hydrology: Stage Fluctuations On both lakes, detailed stage records were available. Sand Hill LakeÂ’s record began in 1957 while Lake Ma gnoliaÂ’s record started in 1958 (Figure 30). Although the records date back over 40 years, the data fre quency changes with time. For each lake, the data frequency can range from daily to monthl y. To avoid bias from periods that have a higher data frequency, the data set was stre ngthened using linear in terpolation to create daily readings for the entire period of record. This met hod cannot recover minor stage fluctuations lost due to sparse data colle ction, however this loss should not have much effect on the determination of the FH, AVE, and FL lake levels.

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48 35 36 37 38 39 40 41 42 43 44 45 195019601970 198019902000 DateLake Stage (m NGVD) Figure 30. Available stage records for Lake Magnolia and Sand Hill Lake. The FH, AVE, and FL levels were determined by calculating the 20th, 50th, and 80th percentiles of the interpol ated stage records. Lake stages from the strengthened records were matched with the corresponding groundwater cross-sections for each transect and for several dates during the st udy. The calculated FH, AVE, and FL were used to guide the study to accomplish Objective 2. Objective 2 – Develop soil-ba sed lake stage indicators Using the initial soil morphology investigations for each transect and the knowledge gained from the results of Obj ective 1, the study was focused on developing soil-based lake stage indicators. To do this, areas near each transect that were believed to be undisturbed were surveyed so the mor phology of the soils at the FH, AVE, and FL elevations could be described. S S a a n n d d H H i i l l l l L L a a k k e e L L a a k k e e M M a a g g n n o o l l i i a a

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49 Initial Morphology Investigations Each transect was investigated for soil -based LSI potential. Focusing on the FH, AVE, and FL elevations, the soil morphol ogy at each transect was recorded for comparison to the hydrologic cross section at that transect. Transects 1 and 5 on Sand Hill Lake and Transect 1 on Lake Magnolia we re chosen for detailed study because of their similar morphologies and ab sence of groundwater seepage. Detailed Morphology Investigations At each transect selected for detailed investigation, proximate areas that were believed to have experienced little distur bance from wave action and surface erosion were chosen for detailed study. This allo wed for observation of the undisturbed soil morphology across the FH – FL elevation ra nge (Figure 31). Once undisturbed areas were identified, elevations in those areas surveyed to determine the locations of the FH, AVE, and FL (Figure 32). Once these levels were located, a trench was dug to expose the soil morphology (Figure 33). The trenches were dug perpendicula r to the topographic contours. The trenches were approximatel y 0.5m wide, 0.5m deep with lengths that ranged from 4m to 5m. For all three tren ches, the upland end wa s higher in elevation than the FH while the lakeside end was lower in elevation than the FL. For the duration of the study, drought conditions caused lake levels to decline. The resulting dry conditions of the soil facilitated the investigations (Figures 34 and 35).

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50 F H A V E F L Lake Levels N o n H y d r i c S o i l s H y d r i c S o i l s Hydric/Non-Hydric Boundary T r e n c h Ground Water L a k eU p l a n d s Figure 31. Block diagram showing the layout of the trench used for detailed soil morphology investigations. The trench is perp endicular to the surface elevation contours and spans the Frequent High (FH), Average (A VE), and Frequent Low (FL) elevations.

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51 Figure 32. Surveying an undistur bed area near Transect 1 to locate the FH, AVE, and FL elevations (Sand Hill Lake). Some vegeta tion was removed to facilitate surveying. Figure 33. Trench in an undisturbed area near Transect 1 (Sand Hill Lake). On this trench red flags mark the location of the upper and lower limits of the Frequent High, Average, and Frequent Low.

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52 Figure 34. Exposed lake bottom resulting from low lake levels (Sand Hill Lake). Lake levels are below the FH, AVE, and FL elevations. Figure 35. Exposed lake bottom resulting from low lake levels (Lake Magnolia). Lake levels are below the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations. FH, AVE, and FL elevations Edge of lake FH, AVE, and FL elevations Edge of lake

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53 Establishing a Soil-Based Lake Stage Indicator Specific morphologic features, change s in morphology, and intensities of morphologic expressions were r ecorded to determine what, if any, consistencies could be seen among the three transects. To qualify as a LSI, the features must be reproducible on both lakes, both in physical appearance and in elevation and be descriptive enough to be applied to other lakes in the SJRWMD. Als o, the genesis of the LSI must be understood so that its presence on other lakes can help understand the genesis of soils surrounding those lakes.

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54 RESULTS AND DISCUSSION Objective 1 – Soil and Hydrologi c Investigation of Study Lakes Lake Scale Groundwater Hydrology Groundwater monitoring of the fi ve transects began on March 16th, 2000. The lake stage and groundwater levels were low and on a downward trend before the study began. For the duration of the study, the lake stag e remained below 40 m NGVD (Figure 36). 38 39 40 41 42 43Mar-00 Apr-00 May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00 Dec-00 Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01DateLake Stage (m NGVD) Highest lake stage during groundwater monitoring (39.8 m on 09/12/2000) Lowest lake stage during groundwater monitoring (39.6 m on 07/10/2000) Lake stage at end of groundwater monitoring (39.65 m on 01/25/2001) Lake stage at beginning of groundwater monitoring (39.79 m on 03/16/2000) Figure 36. Sand Hill Lake stage fluctuations occurring during the study. Black arrows highlight the lake stages occurring at the beginning and end of the groundwater monitoring. Orange arrows highlight the highe st and lowest lake st ages occurring during hydrologic monitoring. Groundwater levels on each transect of Sa nd Hill Lake fluctuates with the lake stage. For all five Sand Hill Lake transects, the lowest groundwater levels occurred at the lowest lake stage. The highest groundwater levels occurred at the highest lake stage.

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55 The lowest lake stage during the st udy was 30.6m NGVD occurring on July 10th 2000. The highest lake stage during the stu dy was 30.8m NGVD occurring on September 12th, 2000 (Figured 37 – 41). The monitoring wells at Lake Magnolia were vandalized before data could be collected. 35 40 45 50 55 60 05101520253035 Distance Along Transect (m)Elevation (m NGVD ) Lake Stage -9/12/2000 Water Table 9/12/2000 Lake Stage -7/10/2000 Water Table 7/10/2000 Well Locations Soil Surface Figure 37. Hydrologic cross-section for Transect 1 on Sand Hill Lake.

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56 35 40 45 50 55 60 05101520253035 Distance Along Transect (m)Elevation (m NGVD ) Water Table 9/12/2000 Lake Stage 9/12/2000 Water Table 7/10/2000 Lake Stage 7/10/2000 Well Locations Soil Surface Figure 38. Hydrologic cross-section for Transect 2 on Sand Hill Lake. 35 40 45 50 55 60 05101520253035 Distance Along Transect (m)Elevation (m NGVD ) Lake Stage 9/12/2000 Water Table 9/12/2000 Lake Stage 7/10/2000 Water Table 7/10/2000 Well Locations Soil Surface Figure 39. Hydrologic cross-section for Transect 3 on Sand Hill Lake.

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57 35 40 45 50 55 60 05101520253035 Distance Along Transect (m)Elevation (m NGVD ) Lake Stage 9/12/2000 Water Table 9/12/2000 Lake Stage 7/10/2000 Water Table 7/10/2000 Well Locations Soil Surface Figure 40. Hydrologic cross-section for Transect 4 on Sand Hill Lake. 35 40 45 50 55 60 05101520253035 Distance Along Transect (m)Elevation (m NGVD ) Lake Stage 9/12/2000 Water Table 9/12/2000 Lake Stage 7/10/2001 Water Table 7/10/2001 Well Locations Soil Surface Figure 41. Hydrologic cross-section for Transect 5 on Sand Hill Lake.

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58 Lake-Scale Surface Water Hydrology Although the groundwater monitoring for La ke Magnolia was not possible, lengthy stage data was available for lake-level dete rminations. The data frequency for Lake Magnolia was daily from 1960 through 1978. After 1978, only weekly stage readings were taken (Figure 42). To avoid bias from the 1960Â’s and 1970Â’s, linear interpolation was used to create daily data for the entire period of record (Figure 43). 0 50 100 150 200 250 300 350 4001955 1960 1965 1970 1975 1980 1985 1990 1995 2000DateNumber of Stage Readings Daily Readings Weekly Readings Daily Readings Figure 42. Stage record frequency for Lake Magnolia.

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59 35 36 37 38 39 40 195019601970198019902000 DateLake Stage (m NGVD) Figure 43. Interpolated stage record for Lake Magnolia. Equally spaced data points were necessa ry so that the per centiles calculated represented the actual percent exceedences of the lake-stage fluctuations for the entire period of record. If unaltere d, the statistics calculated fr om the original data would suggest FH, AVE, and FL levels that desc ribed mainly the hydrology of the 1960Â’s and 1970Â’s. Since that period of time had sma ller fluctuations than the 1980Â’s and 1990Â’s, the FH, AVE, and FL calculated from the orig inal data would have shown less variability than the FH, AVE, and FL calculated from the interpolated data set. The FH-FL range for Lake Magnolia was only a 0.44m elevation difference (Table 2). This very narrow elevation difference can also be observed fr om a stage duration curve (Figure 44). The flat slope of the curve shows the small variabili ty in lake stage elevations. The steep drop at the lower end of the curve near the 90th percentile suggests that the lower lake stages

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60 are more extreme than the higher lake stages . This could possibly indicate a changing hydrology. Table 2. Lake-stage statistics based on La ke Magnolia interpolated stage data. Lake Level% ExceedenceLake Stage (m NGVD) 1538.12 2538.06 4537.96 5537.92 7537.80 8537.67 Frequent Low Frequent High Avaerage FL AVE FH 35.0 36.0 37.0 38.0 39.0 40.0 0102030405060708090100 Percent ExceedenceElevation (m) Figure 44. Stage duration curve for Lake Magno lia (blue line). Orange bands represent the percent exceedence range for the Frequent Low (FL), Average (AVE), and Frequent High (FH). Average

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61 Lengthy stage records were also available for Sand Hill Lake. Again, data frequency was inconsistent. Daily readi ngs were available from 1990 to present, however, only weekly or monthly readings were available prior to 1990 (Figure 45). Linear interpolation was again used to strengthen the data (Figure 46). Percentiles were calculated from the interpolated data to determine the FH, AVE, and FL of Sand Hill Lake (Table 3). The FH-FL range was 0.27 m. The stage-duration curve for Sand Hill Lake (Figure 47) shows a more symmetry, suggesting the highs and lows are more balanced than on Lake Magnolia. 0 50 100 150 200 250 300 350 4001955 1960 1965 1970 1975 1980 1985 1990 1995 2000DateNumber of Stage Readings Daily Readings Monthly Readings Weekly Readings Weekly Readings Monthly Readings Figure 45. Stage record count for Sand Hill Lake.

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62 38 39 40 41 42 43 195019601970198019902000 DateLake Stage (m NGVD) Figure 46. Interpolated stage record for Sand Hill Lake. Table 3. Lake stage statistics based on Sand Hill Lake interpolated stage data. Lake Level% ExceedenceLake Stage (m NGVD) 1540.24 2540.20 4540.12 5540.09 7540.03 8539.97 Frequent High Avaerage Frequent Low Average

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63 FL AVE FH 38 39 40 41 42 43 0102030405060708090100 Percent ExceedenceElevation (m) Figure 47. Stage duration curve for Sand Hill La ke (blue line). Orange bands represent the percent exceedence range for the Frequent Low (FL), Average (AVE), and Frequent High (FH). Objective 2 – Develop soil-ba sed lake stage indicators Initial soil morphological i nvestigations of each transect provided insight to identify the areas eligible for detailed so il morphological investigations. These were areas that appeared to have little groundwater seepage, and therefore, were influenced by lake-stage fluctuations. Initial Soil Morphol ogy Investigation The soils at all of the stations on th e non-seepage slopes (Transects 1, 3, and 5 on Sand Hill Lake and Transect 1 on Lake Magnol ia) were Entisols. The upland soils of each transect looked very similar. Other th an the accumulation of organic matter in the A horizons, there was very little evidence of pedogenesis in any of the upland soils. Each soil had a thin A horizon underlain by multip le C horizons. Although the A horizons did

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64 vary slightly in color and th ickness between stations, all so ils had Ochric epidons (Soil Survey Staff, 1999). The C horizons were 10Y R7/1 or 10YR 8/1 with either a sand or coarse sand particle size. Since the sands were uncoated, there was no morphology that allowed for water table determinations. The sands were probably uncoated before th ey were deposited. If the sands were coated before deposition, then it is possibl e that an extremely deep spodic horizon exists on all transects. The C horizons would then be E horizons. This is unlikely since no evidence of spodic horizon formation was id entified on the wetter portions of the transects. The likely scenario is that th e sands were uncoated upon deposition. If the sands did not have coatings at the time of deposition, then there was no material to be illuviated by water movement. This explains why no evidence of water table fluctuations were found on the upland portions of any of the non-seepage transects. Hydric soils covered a small area on each of these transects. Except for Transect 3 on Sand Hill Lake, all the hydr ic soils on the non-seepage tr ansects were dominated by stratified A and C layers (Figure 48). Transe ct 3 of Sand Hill Lake did not have stratified layers (Figure 49). The soils of Transect 3 also had a much larger sand grain size than the other transects. Observations of wave action and wind dire ction coupled with th e larger sand grain size suggest that the soils near Transect 3 on Sand Hill Lake formed in a high energy environment. ItÂ’s likely that the stratified layers that formed on the other non-seepage, lower energy transects formed briefly on near Transect 3 during s easons of calm weather and then were destroyed by wave act ion during windy seasons (Figure 50).

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65 Figure 48. Typical stratified mineral layers. Stra tifications are alternat ing layers of A and C horizons. Each A horizon is a layer of sa nd coated with organic matter that formed when the layer was at the soil surface, during lower lake levels. In times of flooding, a layer of uncoated sands was deposited on top of the surface A horizon, creating a C horizon. Figure 49. Soils sampled from the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations near Transect 3 (Sand Hill Lake). Transect 3 is located on the lake shore that is affected by hi gh energy waves. These waves do not permit stratified layer formation. A A h h o o r r i i z z o o n n s s C C h h o o r r i i z z o o n n s s F F H H A A V V F F L L

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66 Figure 50. Dominant wind direction of Sand H ill Lake. Wind speed coupled with a 3km fetch results in high energy wa ve action near Transect 3. The soils at the all stations on the seep age slopes (Transects 2 and 4 on Sand Hill Lake and Transect 2 on Lake Magnolia) were ei ther Histosols or Inceptisols with Histic epipedons. The landscapes near Transects 2 and 4 on Sand Hill Lake had very flat slopes and extensive wetlands. The soils occurring n ear both of these tran sects were Histosols (Figures 51A and 51B). The landscape near Transect 2 on Lake Magnolia was steeper S S a a n n d d H H i i l l l l L L a a k k e e L L a a k k e e M M a a g g n n o o l l i i a a T T r r a a n n s s e e c c t t 1 1 T T r r a a n n s s e e c c t t 2 2 T T r r a a n n s s e e c c t t 3 3 T T r r a a n n s s e e c c t t 4 4 T T r r a a n n s s e e c c t t 5 5 T T r r a a n n s s e e c c t t 1 1 T T r r a a n n s s e e c c t t 2 2 W W i i n n d d D D i i r r e e c c t t i i o o n n

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67 and had a less extensive wetland. Inceptisols with a Histic epipedons occurred on this landscape (Figure 52). Figure 51. Histosols occurring near on the seepage slopes of Sand Hill Lake. The Histosols near Transect 2 (A) and Transect 4 (B) were over 1 m thick. The Histosols occurred not only across the Frequent High – Frequent Low range, but also occurred at elevations several meters above that range. This indicates a larg e amount of groundwater seepage occurring on these slopes. A A B B

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68 Figure 52. Inceptisol with a Histic epipe don occurring near Transect 2 on (Lake Magnolia). The presence of a Histic epipe don instead of stratified layers indicates groundwater seepage occurs on this slope. The organic horizons in the Histosols a nd Inceptisols on these seepage transects were Oe horizons. These moderately decompos ed organic horizons ranged in thickness from 20 cm in the Inceptisols to more than 100 cm in the Histosols. The seepage slopes were flat compared to the non-seepage slope s. The wetlands and hydric soils extended for several hundred meters along across the landscape, at eleva tions well above the influence of surface water flooding from lake stage fluctuations. Since seepage greatly influences soil formation on these slopes, they were not chosen for detailed investigation. The sites chosen for detailed study were Tr ansects 1 and 5 from Sand Hill Lake and Transect 1 from Lake Magnolia (Figure 53). H H i i s s t t i i c c E E p p i i p p e e d d o o n n

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69 Transects HydrographyWater Wetland Elevation (m NGVD)30 40 40 50 50 60 60 70 70 80 Elevation (m NGVD) 0.500.5Kilometers N E W S Figure 53. Transects chosen for detailed study at Sand Hill Lake and Lake Magnolia. Detailed Soil Morphological Investig ation of Transect 1 on Sand Hill Lake Stratified layer morphology occurred across the FH – FL range (Figure 54). From the beginning of the trench (landscape positions above the FH) to the upper limit of the FH, the surface layer was a 5 – 15cm thick Oe horizon. Across the FH range, this Oe horizon was stratified by uncoated quartz sa nds creating an Oe and C horizon that overlaid stratified mineral layers (Figure 55). The stratified minera l layers make up the A and C combination horizon. The stratified mineral layers were parallel and ge nerally continuous for over a meter. Since the stratified mineral layers were deeper in the soil at the higher landscape positions of the trench and since they were horizontal, th eir depth from the surface decreased as the surface elevation decreased. At landscape positions immediately below the FH, the stratified hemic layers terminated and the stratified mineral layers intersected the surface. Transect1 Transect5 Transect 1

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Figure 54. Trench near Transect 1 exposing the soil morphology at th e Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake). F F L L A A V V E E F F H H T T o o L L a a k k e e 70

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71 Figure 55. Epipedon near the Frequent High (F H) level showing both stratified hemic and stratified mineral layers (located on Sand Hill Lake Transect 1). At this point the stratified mineral la yers increased in number, decreased in thickness, and increased in contrast. The la yers reached a maximum number and contrast around the AVE and then decreased in number at lower landscape positions (Figure 56). At landscape positions between the AVE and FL , the number of stratified mineral layers decreased. At the FL, the number of stratifi ed mineral layers was 20% of the maximum (Figure 57). Below the FL, the layers becam e diffuse (Figure 58). Figure 59 summarizes the soil morphology of the entire trench. Stratified Layers Mineral Stratified Hemic Layers T T o o L L a a k k e e F F H H

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72 Figure 56. Epipedon showing the maximum number of mineral stratified layers (located on Sand Hill Lake Transect 1). The maxi mum number occurs at the Average (AVE). Figure 57. Epipedon showing the 20% of the maximum number of stratified mineral layers (located on Sand Hill Lake Transect 1). This occurs at the Frequent Low (FL). T T o o L L a a k k e eF F L L Maximum Number of Stratified Mineral Layers A A V V E E T T o o L L a a k k e e 20% of the Maximum Number of Stratified Mineral Layers

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73 Figure 58. Epipedon showing diffuse stratified layers occurring below the Frequent Low (located on Sand Hill Lake Transect 1). T T o o L L a a k k e e D D i i f f f f u u s s e e l l a a y y e e r r s s W W a a t t e e r r T T a a b b l l e e L L o o w w E E n n d d o o f f T T r r e e n n c c h h

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Figure 59. Trench near Transect 1 exposing the soil morphology at th e Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake). F F L L A A V V E E F F H H T T o o L L a a k k e e Stratified hemic layers Maximum number of stratified mineral layers 20% of the maximum number of stratified mineral layers 7 4

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75 Detailed Soil Morphology Investigation of Transect 5 on Sand Hill Lake The soil morphology of Transect 5 was simila r to Transect 1. Stratified layer morphologies occurred across the FH – FL elevation range (Figure 60). From the beginning of the trench (landscape positions above the FH) to the upper limit of the FH, the surface layer was a 5 – 10 cm thick Oe hor izon. Across the FH range, this Oe horizon was stratified by uncoated quartz sands crea ting an Oe and C hor izon that overlaid stratified mineral la yers (Figure 61). The stratified minera l layers make up the A and C horizon. The stratified mineral layers were level and generally continuous for over a meter. At landscape positions immediately below the FH, the stratified hemic layers terminated and the stratified mineral layers intersected the surface. At this point the stratified mineral layers increased in number, decreased in thickness, and incr eased in contrast. The layers reached a maximum number and contrast around the AVE and then decreased in number at lower landscape positions (Figure 62). At landscape positions between the AVE and FL, the number of stratified mineral la yers decreased. At the FL, th e number of stratified mineral layers was 20% of the maximum (Figure 63). Below the FL, the layers became diffuse. Figure 64 shows the soil morphol ogy of the entire trench.

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Figure 60. Trench near Transect 5 exposing the soil morphology at th e Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake). F F H H A A V V E E F F L L T T o o L L a a k k e e 76

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77 Figure 61. Epipedon near the Frequent High (F H) level showing both stratified hemic and stratified mineral layers (located on San Hill Lake Transect 5). Figure 62. Epipedon showing the maximum number of mineral stratified layers (located on Sand Hill Lake Transect 5). The maxi mum number occurs at the Average (AVE). Hemic Stratified Layers T T o o L L a a k k e e F F H H Maximum Number of Mineral Stratified Layers A A V V E E T T o o L L a a k k e e

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78 Figure 63. Epipedon showing the 20% of the maximum number of stratified mineral layers (located on Sand Hill Lake Transect 5). This occurs at the Frequent Low (FL). F F L LT T o o L L a a k k e e 20 % of Maximum Number of Mineral Stratified Layers

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Figure 64. Trench near Tr ansect 5 exposing the soil morphology at the Frequent High (FH), Average (AVE), and Frequent Low (FL) (Sand Hill Lake). F F H H A A V V E E F F L L T T o o L L a a k k e e Stratified hemic layers Maximum number of stratified mineral layers 20% of the maximum number of stratified mineral layers 79

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80 Soil Morphology Investigation – An Overview Transects 1 and 5 on Sand Hill Lake and Tr ansect 1 on Lake Magnolia had similar epipedon morphologies across the FH, AVE, an d FL elevation range. Trenches dug at each transect showed the morphologies were dom inated by stratified layers (Figures 65 67). At the upper sections of the trenches, he mic and stratified hemic layers were present at the surface (Figures 68 and 69). In th e middle sections of the trenches, stratified mineral layers were present at the surface (Figure 70). In the lower portions of the trenches, more diffuse and thic ker stratified mineral layers were present at the surface (Figure 71). These stratified layer morphologies indicat e the soils are frequently flooded. The frequency of flooding is probabl y the major factor contribut ing to the variations in stratified layers across the FH-FL range. Soils that are fl ooded a majority of the time, i.e. the FL soils, have fewer and less distinct layers than the AVE and FH soils. The A horizons in these FL soils can only form wh en lake levels are low enough to expose the soil surface. By definition of the FL, this occu rs only 20% of the time. The other 80% of the time, the soil is flooded. The duration of this flooding is probabl y sufficient to cause the diffuse appearance of the darker stra tifications of the FL soils, the A horizons. The AVE soils by definition experience fl ooded and drained conditions equally. The frequency of flooding at this elevation is greater than the FL or FH. This frequency allows for many A horizons to form and then be covered by uncoated sands from the lake bottom. In both the FL and AVE soils, th e only vegetation that can grow quick enough during the drained conditions are likely herbaceo us plants and algae. This would account for the lack of significant organic matter build up in these stratified A horizons.

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81 The FH soils are probably soils that we re once AVE soils, but after soil deposition from wave action, or erosion from more upla nd positions, were elevated above the AVE. Once above the AVE, the soil su rface would have experience d less frequent flooding and more prolonged drainage. These conditions would be drier than the FL and AVE, but wet enough to favor organic matter accumulation from vegetation. This vegetation would have more opportunity to deposit organic matter, thus building a hemic layer. This layer would be stratified by uncoated sands from flooding at the FH and continuous above the FH.

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82 Figure 65. Trench showing soil morphology across the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations of Transect 1 (Sand Hill Lake). T T o o L L a a k k e e F F H H ( ( s s t t r r a a t t i i f f i i e e d d h h e e m m i i c c l l a a y y e e r r s s ) ) A A V V E E ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) ) F F L L ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) )

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83 Figure 66. Trench showing soil morphology across the Frequent High (FH), Average (AVE), and Frequent Low (FL) elevations of Transect 5 ( Sand Hill Lake). T T o o L L a a k k e e F F H H ( ( s s t t r r a a t t i i f f i i e e d d h h e e m m i i c c l l a a y y e e r r s s ) ) A A V V E E ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) ) F F L L ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) )

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Figure 67. Trench across the Frequent High (FH), Average (AVE), a nd Frequent Low (FL) elevations of Transect 1 (Lake Magnolia). T T o o L L a a k k e e F F H H ( ( s s t t r r a a t t i i f f i i e e d d h h e e m m i i c c l l a a y y e e r r s s ) ) A A V V E E ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) ) F F L L ( ( s s t t r r a a t t i i f f i i e e d d m m i i n n e e r r a a l l l l a a y y e e r r s s ) ) 8 4

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85 Figure 68. Typical hemic layer occurring abov e the Frequent High of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. Hemic Layer (Oe)

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86 Figure 69. Typical stratified hemic layers o ccurring at the Fre quent High of the nonseepage slopes on Lake Magnolia and Sand Hill Lake. Stratified Hemic Layers ( Oe & C )

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87 Figure 70. Typical stratified mineral layers occu rring at the Average and Frequent Low of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. Stratified Mineral Layers (A & C) C

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88 Figure 71. Typical diffuse stratified hemic laye rs occurring below the Frequent Low of the non-seepage slopes on Lake Magnolia and Sand Hill Lake. Stratified mineral Layers (A & C) D D i i f f f f u u s s e e L L a a y y e e r r s s

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89 Soil-Based Lake-Stage Indicators For Sand Hill Lake Once the morphologies common to Transect s 1 and 5 on Sand Hill Lake had been identified the elevations of those features were survey ed. Appendix A contains the calculated elevations of each percent exceedence, from 0% to 100%, based on the interpolated stage data for Sand Hill Lake. The surveyed elevations were compared to the calculated elevations to determine at what percent exceed ence each morphological feature occurred. Tables 4 and 5 show the f eatures associated with the elevations of Transects 1 and 5 respectively. On Transe ct 1, the elevation of the middle of the stratified hemic layers was 40.23 m NGVD, a 17% exceedence. On Transect 5, the average elevation of the stra tified hemic layers was 40.21 m NGVD, a 21% exceedence. Averaging those elevations yielded 40.22 m NGVD. That was the 20% exceedence for Sand Hill Lake (Appendix A). Based on these results, the average elevation of Sand Hill Lake stratified hemic layers was a very good indication of the Sand Hill Lake FH. Averaging the elevations of the maximum number of stratified mineral layers at Transects 1 and 5 on Sand Hill Lake yielde d an elevation of 40.135 m NGVD which was the 43% exceedence for Sand Hill Lake. Th is fell just outside the AVE percent exceedence range of 45-55%. For Sand Hill Lake, the average elevation of the maximum number of stratified mineral layers is an indication of the upper limit of the AVE. Averaging the elevations of the 20% of th e maximum number of stratified mineral layers yielded an elevation of 40.00 m NGVD which was the 81% exceedence for Sand Hill Lake. This fell within the FL percen t exceedence range of 75-85%. For Sand Hill Lake, the average elevation of 20% of the ma ximum number of stra tified mineral was a very good indication of the FL.

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90 Table 4. Elevation features occurring near Transect 1 on Sand Hill Lake. Elevations are in meters National Geodetic Vertical Datum (NGVD). Elevation (m NGVD) Exceedence Beginning of stratified hemic layers42.289% Frequent High (FH) upper limit40.2415% Middle of stratified hemic layers40.2317% Frequent High (FH) lower limit40.2025% End of stratified hemic layers40.1829% Average (AVE) upper limit40.1345% Maximum number of stratified mineral layers40.1247% Average (AVE) lower limit40.0955% Frequent Low (FL) upper limit40.0375% 20% of maximum number stratified mineral layers40.0278% Frequent Low (FL) lower limit39.9785% Feature

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91 Table 5. Elevation features occurring near Transect 5 on Sand Hill Lake. Elevations are in meters National Geodetic Vertical Datum (NGVD). Feature Elevation (m NGVD) Exceedence Beginning of stratified hemic layers40.2513% Frequent High (FH) upper limit40.2515% Middle of stratified hemic layers40.2121% Frequent High (FH) lower limit40.2025% End of stratified hemic layers40.1733% Maximum number of stratified mineral layers40.1442% Average (AVE) upper limit40.1345% Average (AVE) lower limit40.0955% Frequent Low (FL) upper limit40.0375% 20% of maximum number stratified mineral layers39.9884% Frequent Low (FL) lower limit39.9785% Soil-Based Lake Stage Indi cators for Lake Magnolia Because access to Lake Magnolia was extremely limited, elevations of soil morphologic features of the trench near Tr ansect 1 were not r ecorded. The general locations along the transect of soil featur es were noted and photographed. Enough detail was captured for Lake Magnolia to serve as a check that similar morphologies existed at similar exceedences to the morphologies at Sand Hill Lake. Soil-Based Lake Stage Indicators for Both Lakes Based on the results from the detailed study of Sand Hill Lake so ils and the initial study of Lake Magnolia soils, three soil-based LSIs are proposed for both lakes (Table 6)

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92 Table 6. Proposed soil-based lake stage indi cators for Lake Magnolia and Sand Hill Lake. Frequent High (FH), Average ( AVE), and Frequent Low (FL), can each be indicated with a soil-based Lake Stage Indicator. Flood Event Percent Exceedence Soil-Based Lake Stage Indicator FH20% The average surface elevation of soils that have stratified hemic layers Upper Limit of the AVE 45% The average surface elevation of soils that have the maximum number of stratified mineral layers FL80% The average surface elevation of soils that have 20% of the maximum number of stratified mineral layers The AVE is not directly indicated by any so il-based LSIs. An accuracy error will occur when users of these LSIs average the FH and FL elevations to calculate the AVE. Because the AVE is not a statistical average of the lake stage records, this will only yield the AVE on certain types of lakes. Lakes with symmetrical stage/duration curv es such as Sand Hill Lake (Figure 72) have floods and droughts of equal magnitude. On these lakes, the elevation difference between the FH and the AVE is equal to the elevation difference between the AVE and FL. For these lakes, the AVE can be appr oximated by the average elevation of the FH and FL. However, lakes that have asymmetr ical stage/duration curves, such as Lake Magnolia (Figure 73), do not experience drough ts and floods of equal magnitude. For these lakes, the elevation difference betw een the FL and AVE is not equal to the elevation difference between the FH and the AVE . Therefore, averaging the elevation of the FL and FH on these lake s would not indicate the AVE.

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93 38 39 40 41 42 43 0102030405060708090100 Percent ExceedenceElevation (m) Figure 72. Stage/Duration Curve for Sand Hill Lake. Note the symmetry. Lows and Highs are of equal elevations above and below the Average. 35.0 36.0 37.0 38.0 39.0 40.0 0102030405060708090100 Percent ExceedenceElevation (m) Figure 73. Stage/Duration Curve for Lake Magno lia. Note the asymmetry. The lows are much greater in magnitude than the Highs.

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94 CONCLUSIONS Many of the lakes in the SJRWMD are in need of immediate attention. Low water levels brought on by recent droughts and increased groundwater pumping have caused sandhill lakes to become the current focu s of the SJRWMD. Because many of these sandhill lakes do not have stage records th at completely describe their current hydrologies, the SJRWMD needed soil-based LS Is that would be applicable to these lakes. The purpose of this study was to de velop soil-based LSIs for sandhill lakes in the SJRWMD. Lake Magnolia and Sand Hill Lake served as excellent study lakes for the development of soil-based LSIs. The comb ination of undisturbed soils, lengthy stage records, small stage fluctuations, and curre nt drought conditions provided an opportunity to view a range of soil morphologic ch anges in a relatively small study area. Since most lakes in the area have shallow lake bottoms near the lake shore, stage fluctuations of three or four meters can transl ate into a lake shore that migrates tens to hundreds of meters. The stage fluctuations of both study lakes were less than two meters for the entire period of record, which was almo st 50 years for both lakes. Combined with the flat land slope, this tran slated into only a 3-4 meter area of soil that experienced flooding from lake waters. The timing of the st udy was fortuitous since lake levels were down below the FH for the entire study. This allowed us to explore and view the continuous soil morphology across the FH-F L elevation range under dry conditions.

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95 Transects of surficial aquifer monitoring wells upslope from the FH-FL elevation range provided groundwater data to unders tand why the hydric and sub-aqueous soil morphology of the FH-FL range differed around the lake. Seepage slopes provided a constant source of water to the FH-FL soils, even when lake levels were down. The morphologies of these soils reflect the consta nt saturation from gr oundwater instead of a variable saturation from lake-stage fluctuat ions. The soils on th e FH-FL areas of nonseepage slopes were dry since the lake leve ls were down, and are assumed to only be wet when lake levels rise. The stratified soil morphologies reflected the lake stage fluctuations. When the FH, AVE, and FL elev ations were calculated from the lake stage data, it was discovered that at the FH elevation range, stratifie d hemic layers are present. Above the FH, the hemic layer was not strati fied. Below the FH, no hemic layers were present. At the AVE elevation range, the maximum number of stratified mineral layers were present. At the FL, the number of strati fied mineral layers decreased to 20% of the maximum. Also, the layers increased in thickness, and decreased in contrast. At the FH, the transition from solid hemic to stratified hemic indicated the soil experienced occasional flooding from the la ke. Wave action probably deposited the uncoated sands, thereby creating the stratified he mic layers. The mineral stratified layers beneath the hemic layers indicated that the soil surface at that location was previously lower in elevation, thus facilitating the form ation of stratified mi neral layers. After erosion from higher elevations or sediment deposition from ve ry high lake levels, the soil surface elevation increased lead ing to less frequent flooding.

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96 The mineral stratified layers occur under th e frequent fluctuations of lake stage around the AVE elevation. The lighter laye rs are uncoated sand grains, C horizons, deposited by wave action while the darker la yers are thin A horizons that were covered before much organic matter could accumulate. Because of the dr ought conditions, large areas of herbaceous vegetation were creati ng A horizons in the exposed lake bottom, below the FL. These areas will likely be c overed by sands when the lake returns to a higher stage. When these A horizons are covered and flooded for extended periods of time, organic matter is “washed out” of the A horizons making the boundary between the A and C horizons diffuse. This explains why soils at and below the FL have fewer yet thicker and more diffuse stratified mineral layers. The concept of stratified layers chan ging in number, thickness, contrast, and composition across the FH-FL elevation range is one that can be applied to similar sandhill lakes. It is possible that this gradient of morphologies may only occur on relatively undisturbed lakes with small la ke stage fluctuations. Different soil morphologies may exist on lakes with very larg e stage fluctuations (i.e. Lake Brooklyn). A major assumption that was made when de veloping these LSIs was that the soil morphology reflected the hydrology that exis ted during the entire period of hydrologic record. The persistence of these stratified layers is unknown. It is unknown whether the indicators will migrate, if th e hydrology of a lake changes drastically. In almost all soils, regardless of hydrology, A horizons form. It is assumed that layers of stratified A and C horizons would persist if the hydrologic regime shifted down, creating a drier environment for the soils of the former FH-FL elevation range. Based on the

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97 observations of the diffuse stra tified mineral layers at the FL and lower elevations, it is possible that if stratified mine ral layers had formed at lower elevations to reflect a previously lower set of lake stage fluctuati ons, then those stratified layers would become diffuse and disappear as the set lake stage fl uctuations increased. If this occurs, then stratified mineral layers reflect current lake stage fluctuations, or previous lake stage fluctuations that were higher. Based on these research findings, the soilbased LSIs should be tested on other sandhill lakes. These LSIs s hould be verified on similar la kes first, then a study should be conducted on sandhill lakes with lake-stage fluctuations that are different from Lake Magnolia and Sand Hill Lake. In-situ studies could be conducted where the soils at the FH-FL are artificially drained or flooded to test for morphologic pe rsistence. Once the geographic distribution of th eses and other soil morphol ogies are understood in the context of hydrology, these and other soil-based lake stage indicators can be used to determine lake stage fluctuations fo r lakes with little or no stage data.

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98 APPENDIX LAKE STAGE STATISTICS Table A-1. Lake stage statisitic s calculated for Sand Hill Lake. StageStage ( m NGVD ) ( m NGVD ) 0%40.4726%40.20 1%40.4027%40.19 2%40.3728%40.19 3%40.3429%40.18 4%40.3330%40.18 5%40.3131%40.18 6%40.3032%40.17 7%40.3033%40.17 8%40.2934%40.17 9%40.2835%40.16 10%40.2736%40.16 11%40.2637%40.16 12%40.2638%40.15 13%40.2539%40.15 14%40.2540%40.15 15%40.2441%40.14 16%40.2442%40.14 17%40.2343%40.13 18%40.2344%40.13 19%40.2245%40.12 20%40.2246%40.12 21%40.2147%40.12 22%40.2148%40.12 23%40.2149%40.11 24%40.2050%40.11 25%40.20 ExceedenceExceedence

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99 Table A-1--continued. StageStage ( m NGVD ) ( m NGVD ) 51%40.1176%40.03 52%40.1077%40.02 53%40.1078%40.02 54%40.1079%40.02 55%40.0980%40.01 56%40.0981%40.00 57%40.0982%39.99 58%40.0983%39.99 59%40.0884%39.98 60%40.0885%39.97 61%40.0886%39.96 62%40.0787%39.95 63%40.0788%39.95 64%40.0789%39.94 65%40.0690%39.93 66%40.0691%39.91 67%40.0692%39.89 68%40.0593%39.87 69%40.0594%39.85 70%40.0595%39.83 71%40.0596%39.80 72%40.0497%39.75 73%40.0498%39.65 74%40.0499%39.54 75%40.03100%39.45 ExceedenceExceedence

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100 Table A-2. Lake stage statisitic s calculated for Lake Magnolia. StageStage ( m NGVD ) ( m NGVD ) 0%38.3826%38.06 1%38.2927%38.05 2%38.2528%38.05 3%38.2329%38.04 4%38.2130%38.04 5%38.2031%38.04 6%38.1932%38.03 7%38.1733%38.02 8%38.1734%38.02 9%38.1635%38.01 10%38.1536%38.01 11%38.1437%38.01 12%38.1338%38.00 13%38.1339%37.99 14%38.1240%37.99 15%38.1241%37.99 16%38.1142%37.98 17%38.1043%37.97 18%38.1044%37.97 19%38.1045%37.96 20%38.0946%37.96 21%38.0847%37.95 22%38.0848%37.95 23%38.0749%37.95 24%38.0750%37.94 25%38.06 ExceedenceExceedence

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101 Table A-2--continued. StageStage ( m NGVD ) ( m NGVD ) 51%37.9376%37.79 52%37.9377%37.78 53%37.9278%37.77 54%37.9279%37.76 55%37.9280%37.75 56%37.9181%37.74 57%37.9182%37.73 58%37.9083%37.71 59%37.9084%37.69 60%37.8985%37.67 61%37.8886%37.65 62%37.8887%37.63 63%37.8788%37.61 64%37.8789%37.60 65%37.8690%37.57 66%37.8691%37.53 67%37.8592%37.49 68%37.8593%37.41 69%37.8494%37.31 70%37.8495%37.21 71%37.8396%36.94 72%37.8297%36.60 73%37.8298%36.23 74%37.8199%36.01 75%37.80100%35.57 ExceedenceExceedence

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102 LITERATURE CITED Boniol, D., W. Marvin, D. Munch. 1993. Mappng Recharge to the Floridan Aquifer Using a Geographic Information System. St. Johns River Water Management District Technical Publication: SJ 83-5. Clark, W.E., R.H. Musgrove, C.G. Menke, J.W. Cagle. 1963. Hydrology of Brooklyn Lake Near Keystone Heights, Florida. Florida Geological Society Report of Investigation No. 33. State governme nt printing office, Tallahassee. Clark, W.E., R.H. Musgrove, C.G. Menke, J. W. Cargle. 1964. Water Resources of Alachua, Bradford, Clay, and Union Coun ties, Florida. Florida Geological Survey Report of Investigation No. 35. State government printing office, Tallahassee. Demas, G.P., M.D. Rabenhorst. 1999. SubAqueous Soils: Pedogenesis in a Submersed Environment. Soil Sci. Soc. Amer. J. 63:1250-1257 Federal Register. July 13, 1994. Changes in Hydric Soils of the United States. Washington, D.C. Federal Register. In Press. Hydric So ils of the United States. Washington, D.C. Hupalo, R.B., C.P. Neubauer, L.W. K eenan, D.A. Clapp, E.F. Lowe. 1994. Establishment of Minimum Flows and Leve ls for the Wekiva River System. St. Johns River Water Management Distri ct Technical Publication: SJ 94-1. Kinser, P., M.C. Minno. 1995. Estimating the Likelihood of Harm to Native Vegetation from Groundwater Withdrawals. St. J ohns River Water Management District Technical Publication: SJ 95-8. Merritt, M.L. 2001. Simulation of the In teraction of Karstic Lakes Magnolia and Brooklyn with the Upper Floridan Aquifer, Southwester Clay County, Florida. U.S. Geological Survey Water-Resources Investigation Report 00-4204. State government printing office, Tallahassee. Motz, L.H., J.P. Heaney. 1991. Upper Et onia Creek Hydrologic Study Phase I Final Report. St. Johns River Water Management District Special Publication: SJ 91SP5.

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103 Motz, L.H., J.P. Heaney. 1991. Upper Et onia Creek Hydrologic Study Phase II Final Report. St. Johns River Water Management District Special Publication: SJ 92SP18. Rao, D.V. 1982. Frequencies of High and Lo w Stages for Principal Lakes in the St. Johns River Water Management District . St. Johns River Water Management District Technical Publication: SJ 90-2. Rao, D.V., S.A. Jenab, D.A. Clapp. 1990. Rainfall Analysis for Northeast Florida Part V: Frequency analysis of Wet Season a nd Dry Season Rainfall. St. Johns River Water Management District T echnical Publication: SJ 90-3. Robison, C.P. 1992. Surface Water Modeling Study of the Upper Etonia Creek Chain of Lakes Clay County, Florida. St John s River Water Management District Technical Publication: SJ 9203. Schiffer, D.M. 1998. Hydrology of Central Fl orida Lakes: A Primer. U.S. Geological Survey Circular: 1137. State governme nt printing office, Tallahassee. Soil Survey Staff. 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil su rvey. United States Depa rtment of Agriculture – Soil Conversation Service Agriculture Handbook 436. U.S. Gov. Print Office, Washington D.C. Soil Survey Staff. 1999. Soil Taxonomy: A basic system of soil classification for making and interpreting soil su rvey. United States Depa rtment of Agriculture – Soil Conversation Service Agriculture Handbook 436. U.S. Gov. Print Office, Washington D.C. St. Johns River Water Management District Staff. 1992. High Resolution Seismic Reflection Profiling in Selected Lakes in the St. Johns River Water Management District. St. Johns River Water Manageme nt District Special Publication: SJ 92SP3. St. Johns River Water Management Distri ct Staff. 1994. St Johns River Water Management District Minimum Flows and Levels Project Plan Draft. Weatherspoon, R.L., E. Cummings, W.H. Wittstruck. 1989. Soil Survey of Clay County, Florida. Soil Conservation Servic e, U.S. Department of Agriculture. U.S. Gov. Print Office, Washington D.C. Yobbie, D.K., G.C. Chappell. 1979. Summ ary of the Upper Etonia Creek Basin. St. Johns River Water Management Distri ct Technical Publication: SJ 79-5.

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104 BIOGRAPHICAL SKETCH Larry Richard Ellis was born in Jack sonville Beach, Florida, in 1974. He graduated from the University of Florida in the fall of 1998 with a B.S. in environmental science. In the spring of 1999 he entered th e Soil and Water Science Department at the University of Florida in pursuit of a M.S. degree. He studied pe dology and GIS, focusing on the relationships between hydric/s ub-aqueous soils and hydrology.