chapter 12 impact of best management practices …chapter 12 impact of best management practices in...

CHAPTER 12

Impact of best management practices in a coastal watershed

K.T. MorganSouthwest Florida Research and Education Center,Soil and Water Science Department,University of Florida, USA.

Abstract

Draining of wetlands to adapt the coastal plain for agricultural and urban use has occurred in many locations throughout the United States. The Kissimmee River, Lake Okeechobee, and Everglades are part of a vast wetland system that histori-cally extended over 200 miles from the Kissimmee chain of lakes, near Orlando, ending in the mangrove estuaries of Florida Bay, south of Miami. This nutrient-poor wetland system supported a diverse and large community of species across huge seasonal and interannual variation in rainfall. The combination of a subtropi-cal climate and supply of potentially arable land has proven to make South Florida a desirable place to farm and live. With agricultural and urban development of the landscape, several areas of Lake Okeechobee and the Everglades have expe-rienced increased nutrient loading, particularly phosphorus, resulting in shifts in the algae and plant communities found within lakes, marshes, and near-shore marine environments. Reducing this “phosphorus enrichment” is the primary goal of Lake Okeechobee and Everglades restoration efforts brought about by the Everglades Forever Act (EFA). Site-specifi c best management practices (BMPs) to reduce the quantity and improve the quality of runoff leaving agricultural lands have improved the water quality of associated wetlands. Another method used to reduce phosphorus for complying with the EFA includes the development of man-made wetlands, called stormwater-treatment areas (STAs) where phosphorus removal is achieved through the accumulation and burial of peat sediments. These restoration actions should reverse environmental impacts of increased P loading while maintaining the original goals of supporting agricultural production and urban development.

www.witpress.com, ISSN 1755-8336 (on-line) WIT Transactions on State of the Art in Science and Engineering, Vol 33, © 2008 WIT Press

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334 Coastal Watershed Management

1 Introduction

Degradation of water quality in two watersheds in Central and South Florida began with the drainage of these watersheds starting in the 1880s and continuing through the 1960s. The drainage of wetlands and watersheds along the Kissimmee River, Lake Okeechobee, and the Everglades was done to make arable land available for agricultural and urban development. While these actions were taken with little or no regard to their environmental impact, currently some of these actions are now being reversed. However, much environmental damage has occurred and reclamation will be costly, both temporally and monetarily. But these reclamation efforts are essential for the sustainability of agricultural production and increased urban development in the region.

Past actions associated with draining wetlands to adapt the costal plain of south Florida for agricultural and urban use have been repeated in many locations throughout the United States and the world. The current reclamation efforts in the Okeechobee and Everglades watersheds can be used as a model for other impacted costal plains. The reader will see that agricultural best management practices have and will continue to improve water quality in the sensitive ecosystems of south Florida. This chapter will review the hydrology of the Kissimmee River and Everglades eco-systems, changes in land use and agricultural development in South Florida, and resulting water-quality and ecosystem changes. The chapter will conclude with legislative mandates to reclaim these watersheds and current improvements made in water quality in South Florida.

2 Hydrology of the Kissimmee River andEverglades ecosystems

The Kissimmee River and Everglades are part of a vast wetland system that histor-ically extended over 200 miles from the Kissimmee chain of lakes, near Orlando, south through Lake Okeechobee into the freshwater marshes of the Everglades and ending in the mangrove estuaries of Florida Bay, south of Miami (Fig. 1). Water fl ow to the Everglades started with rainfall accumulating in central Flor-ida and slowly fl owing south through the meandering Kissimmee River to Lake Okeechobee. From Lake Okeechobee, the water continued moving slowly south, through the Everglades toward Florida Bay, between the Florida mainland and keys. During this slow progression through the Everglades, the water recharged the Biscayne Aquifer, supplied nutrients for vegetative growth, provided freshwa-ter for fi sh, maintained the food chain for migratory birds, and reduced saltwater intrusion from both the Atlantic Ocean and Gulf of Mexico [2, 3].

The upland ecosystems along the Kissimmee River include pine (Pinus sp. L.) and hardwood forests containing a mixture of temperate and tropical species [34, 44]. Natural land cover includes saw palmetto (Serenoa repens Batr.) and pine fl atwoods, hardwood forests, cypress sloughs, and small isolated wetlands with herbaceous vegetation. In contrast, The Everglades was an expanse of sawgrass


Impact of Best Management Practices in a Coastal Watershed 335

Figure 1: The historical watershed of the Everglades ecosystem.

(Cladium jamaicense Crantz) wetlands and was called the “River of Grass”. The original Everglades extended south from Lake Okeechobee to Florida Bay and was bounded by the swamps of the Big Cypress on the west and Atlantic Ocean on the east [33].

Soils along the Kissimmee River developed over geological time primarily into Spodosols. Spodosols are characterized as having undergone extensive leaching of organic matter and aluminum from the surface horizons [15]. These soils develop



in poorly drained areas with sandy, acidic parent material. The leached horizon is uncoated sands with low water- and nutrient-holding capacities. The most striking property of Spodosols is a black to reddish-brown horizon of amorphous accumula-tions of organic matter and aluminum at a depth of less than 1 m with low hydraulic conductivity, and high cation-exchange capacity [15]. Water falling on the Spodo-sols north of Lake Okeechobee readily penetrate the relatively short distance between the soil surface and accumulates above the spodic horizon, saturating the soil. Water fl ow is then predominately horizontal along the spodic horizon to any point of drainage carrying nutrients it contains. Any water percolating through the spodic horizon would leach nutrient to the nutrient-poor parent material below. At a depth of a few to several meters below the surface, this water enters the lime-stone aquifer system underlying the state of Florida.

Soils south of Lake Okeechobee developed into Histosols. In general, Histisols contain more than 50% organic matter in the upper 80 cm of soil depth [25]. The soils are composed of partially decomposed plant material that accumulates over geological time scales. Morris and Gilbert [24] stated that these soils formed in South Florida from sawgrass since the Holocene period (<10,000 years ago). As with Spodosols, vertical water movement in Histosols of south Florida is limited to a few meters by limestone deposits.

This nutrient-poor wetland system supported a diverse and large community of species across huge seasonal and interannual variation in rainfall [16]. The water level of Kissimmee River and Lake Okeechobee would fl uctuate dramatically with rainfall patterns within their drainage basins. Total annual rainfall varies from less than 1000 mm to almost 2000 mm over a seven- to ten-year cycle [10]. Approxi-mately three-quarters of the annual precipitation occurs during the four-month period from mid-June through September [10, 21, 43]. Water levels within the marshes and lakes of the system rose during the wet seasons and water slowly fl owed south [11]. During wet years, fl ow rates of the Kissimmee River would increase dramatically contributing to substantial increases in lake levels of Lake Okeechobee. Lake Okeechobee would overfl ow its southern rim and contribute a broad sheet of water to the Everglades, increasing water depths and lengthening hydroperiods. Due to the nearly level topography of the Everglades, water within the marshes moved slowly and was maintained for longer periods of time, typically well into the fol-lowing dry season. During the dry season, evaporation exceeded rainfall and water levels would recede [11]. The annual pulse of fresh water into the estuary of Florida Bay created a highly productive interface between the freshwater system and the Gulf of Mexico [23]. The ecosystem supported a huge array of animal species. Large fl ocks of wading birds nested along the interface between the freshwater Everglades and the estuaries [1, 13, 29, 30].

3 Changing land uses of South Florida

The combination of a subtropical climate and supply of potentially arable land has proven to make South Florida a desirable place for humans to live. The popula-tion of this region has increased from only a few tens of thousands in 1900 to over



six million people in 2000 [47]. An increase of almost two million new residents is projected over the next 20 years. This increase in human populations resulted in major changes to the ecosystems of South Florida. Extensive drainage of wetlands and clearing of uplands began in the 1880s to create agricultural lands [19, 20].

Wetlands along the Kissimmee River and around Lake Okeechobee were drained and converted to agricultural lands for the raising of cattle and growing winter vegetables, sugar cane, rice, and sod [20]. The hydrologic connection between Lake Okeechobee and the Everglades was severed to develop agricultural lands and control fl ooding south of the lake. Water that had fl owed from Lake Okeechobee to the Everglades was shunted east to the Atlantic Ocean through the St. Lucie Canal, and west to the Gulf of Mexico through the Caloosahatchee River. As a result, the volume of water fl owing through The Everglades was decreased and the pattern of the water through the ecosystem was signifi cantly altered [7].

More intensive land use is associated with the transition from open space to agriculture and residential uses, necessitating increased fl ood protection. These changes reduce the water available to natural areas. In order to provide increased fl ood protection in developed areas, water tables were lowered. This action reduced both the local storage of groundwater and the probability that local rainfall would recharge well fi elds, which places greater demand on the regional system for water.

4 Agricultural development in South Florida

A large portion (more than 380,000 ha) of the original Everglades that lay imme-diately south of Lake Okeechobee was drained and developed into the Everglades Agricultural Area (EAA). Along the Eastern edge of the Everglades about 1.2 million ha has been developed for urban use. To facilitate this development, construction of an extensive system of canals and levees was built to meet fl ood-control and water-storage needs of growing agricultural and urban development. Called the Central and Southern Florida Control Project, these structures were completed between 1920 and 1960 (Fig. 2). These activities resulted in alterations in the hydrology and water quality of both Lake Okeechobee and the Everglades. Alteration in the hydrology of South Florida included the depth, duration, and timing of annual fl ooding (hydropattern) and the amount of time each year that the ground is covered with water (hyproperiod) [2, 16, 19, 22]. Changes in the timing and fl ow of the water impact many aspects of the ecosystem, causing changes in water quality.

In a recent survey, the area of Histosols in south Florida is estimated to be 0.8 million ha [24]. Approximately 15% of the Histosols in the Everglades were found to be in agricultural production; the major crops in this area are sugarcane and winter vegetables. Decomposition of the organic matter comprising Histosols results from oxidation by aerobic soil micro-organisms when these soils are drained. During decomposition, these soils release nitrogen and phosphorus at rates approaching 1200 and 73 kg ha–1 yr–1, respectively [9, 42]. As the organic matter of Histosols decompose, the soil depth decreases or subsides. The rate of subsidence in south Florida have been estimated to be approximately 2.5 cm yr–1 for the period 1924 to 1978 [37], resulting in as much as 175 cm reduction in soil



depth of some heavily cropped areas over the past 80 years. Improved agricultural practices, such as maintenance of higher water tables and fl ooding of fallow land, implemented in the late 1970s have reduced this rate to approximately 1.5 cm yr–1. As a result, the Histosols in the EAA are becoming increasingly shallow, in some cases less than 20 cm thick. These soils overlie hard limestone rock and may not be able to sustain agricultural production in the near future.

5 Water-quality and ecosystem changes

Historically, the nutrient supply to the Kissimmee River and Everglades watersheds was provided primarily through rainfall, thus, the vegetative communities selected

Figure 2: Alterations in the watershed of the Everglades ecosystem.



for species with low nutrient requirements [16, 32]. However, with agricultural and urban development of the landscape, several areas of Lake Okeechobee and the Everglades have experienced increased nutrient loading [7, 8, 12, 27]. Nutrient infl ows into the Kissimmee River and the Everglades, particularly phosphorus, have been responsible for many of the changes to the ecology of the Lake Okeechobee and the Everglades.

The increased levels of both phosphorus and nitrogen in surface waters of south Florida have resulted in shifts in the algae and plant communities found within lakes, marshes, and near-shore marine environments. In the past, the marshes of the Everglades were characterized by a mixture of sawgrass and slough communities. However, increased nutrients, particularly phosphorus, have resulted in a shift to a community dominated by cattail (Typha latifolia L.) [2, 16]. Due to these changes in the plant communities, food chains have been altered [5].

Therefore, reducing this “phosphorus enrichment” is the primary goal of Lake Okeechobee and Everglades restoration efforts [14, 22]. The Florida legislature passed the Everglades Forever Act (EFA) in 1994 (Section 373.4592, Florida Statutes), which directs the State of Florida to develop a phosphorus criterion for the Ever-glades Protection Area. The criterion numerically interprets an existing narrative standard which states: “In no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic fl ora or fauna”. The EFA mandated the reduction of phosphorus through the reduction of loads and water treatment. Two plans, Lake Okeechobee Protection Plan (LOPP) and Comprehensive Everglades Restoration Plan (CERP), were developed to imple-ment improved agricultural management practices to lower phosphorus through improved on-farm water-management techniques and to construct managed wetlands to reduce phosphorus through vegetative uptake and soil storage [46, 49, 50].

6 Lake Okeechobee protection plan

Lake Okeechobee is approximately 150,000 ha in size and has a drainage basin containing approximately 1.1 million ha. During the last century, agricultural and urban development in the watershed and the construction of the Central and South Florida Project for fl ood control have caused excessive nutrient inputs. By the late 1980s, Lake Okeechobee was highly polluted with phosphorus resulting from point- and nonpoint-source agricultural and urban discharges into the watersheds along the Kissimmee River [5, 7]. The lake also receives large internal loads of phosphorus from the underlying mud sediments, where decades of past nutrient loads have accumulated. Total phosphorus concentration in Lake Okeechobee has almost doubled since the 1970s and chlorophyll levels have signifi cantly increased over the same period [39]. As a result, there have been serious changes in the eco-system, the most visible one being an increased frequency of algal blooms.

Lake eutrophication was attributed primarily to phosphorus loads form agricul-tural runoff in its watershed. The majority of Florida’s 4000 ha of cattle pasture are located in south and central Florida [26]. Much of what was once native sub-tropical wet prairie ecosystem in this region is now managed for grazing. Land-use



changes within these ecosystems have resulted in dramatic changes in the wildlife habitat characteristics and the patterns of nutrient fl ow for upland, marsh, and lake ecosystems [30].

The main focus of the LOPP is to reduce inputs of phosphorus to the lake from the watershed. A key aspect of the restoration program is that it includes cooperation among landowners, local government, and other state and federal agencies. Agri-cultural landowners are encouraged to implement measures to reduce the amount of phosphorus migrating off their land.

Site-specifi c improved agricultural production practices or best management practices (BMPs) improving the quality of runoff leaving agricultural lands are particularly important aspects of the LOPP. The Florida Department of Agricul-ture and Consumer Services has developed a voluntary BMP implementation pro-gram for activities including dairies and cow-calf operations, and vegetables and citrus production [18]. Examples of BMPs that reduce runoff-water quantity are detention ponds and grassed swales. Practices that improve runoff-water quality are reduced fertilizer application rates, ditch sediment control, dairy waste lagoons, and livestock confi nement.

7 Comprehensive Everglades restoration plan

The CERP is the largest of the two restoration plans and is funded, managed and implemented through an unprecedented 50–50 partnership between the sate of Florida and federal government. The purpose of the plan is to re-establish a more natural fl ow of water throughout South Florida, including the Everglades, as well as ensure reliable water supplies for agricultural and urban use and provide fl ood control. Restoring a more natural fl ow of water to the Everglades should result in a long-term, sustainable water supply for South Florida with improved water quality.

The EFA proposed a stringent 100 ppb standard for P in surface water for the entire Everglades with a compliance deadline of December 31, 2003. Landowners, including farmers, in the Okeechobee Basin, pay one-tenth of a mil ad-valorem tax (~$38 million annually) and farmers within the EAA and C-139 basin pay an Agri-culture Privilege Tax (~$11.5 million annually, or ~$60 per ha). Florida is paying the full cost of the water-quality improvements required by the State under the EFA and 50 per cent of the cost to implement the CERP, with the federal government paying the other half. To date, the state of Florida has committed nearly $1.3 billion to clean up the Everglades (EFA) and nearly $1.5 billion to restore a more natural fl ow of water to the River of Grass (CERP).

8 Compliance with the Everglades Forever Act

In 1996, SFWMD determined that the best interim methods to reduce phosphorus for complying with EFA included improved farming practices and the develop-ment of man-made wetlands, called stormwater-treatment areas (STAs). Farmers can choose from a list of approved BMPs and must monitor off-farm discharge for both fl ow volume and P concentration. On-farm studies in the EAA have shown



that a signifi cant portion of the total P load in drainage water leaving farms is in the particulate form [4, 17, 31, 35, 36, 41]. Therefore, most of the BMPs target the reduction of particulate P and sediment loads in drainage water [6, 38]. A primary BMP is fi eld leveling prior to planting to reduce sheet erosion and improve water management. Small raised berms can also be constructed parallel to fi eld ditches and drainage canals. With this BMP, water that may pond on the fi eld after a heavy rain must percolate vertically eliminating sheet fl ow to drainage ditches. Main canal and fi eld ditch sumps can be designed to further reduce off-farm sediment discharge. These sumps are deeper and/or wider areas in canals or ditches upstream of culverts or discharge pumps to reduce water fl ow and allow heavier materials to settle to the bottom. Cleaning and maintenance of drainage ditches and sumps are also prescribed as BMPs. Ditch and sump cleaning removes any debris and veg-etable matter from the drainage system that can contribute to sediment P loading. Ditch maintenance includes establishing vegetated banks for stabilization and use of weed and trash booms to block these materials from leaving the farm.

Evaluations conducted since 1996 have confi rmed that STAs were the best interim step toward achieving the long-term water-quality and hydropattern-restoration goals for the Everglades [40]. These managed wetlands were constructed to remove water-borne nutrients through plant growth and the accumulation of decomposing plant material in a layer of peat. The goal was that by 2006, these technologies will reduce phosphorus in water entering the Everglades by 90 per cent from a decade ago [40].

An important aspect of stormwater-treatment area optimization research is to deter-mine the function of phosphorus retention mechanisms that serve in phosphorus removal. Vegetation growth results in the rapid, short-term nutrient uptake from the soil and water column. These nutrients can be temporarily stored in the vegetative structures of the plants before being released back into the water column from sedi-ments after plant death. The microfl ora community of this wetland system is highly productive, but is greatly impacted by P enrichment [45]. Periphyton (a community of algae, bacteria, and microfauna) proliferate at the soil surface of impacted wetlands and are highly effi cient at reducing P from the water column by immobilization of the nutrient [28, 48]. A nutrient mass balance has been established by measuring the total phosphorus concentration of infl ow water, precipitation, plant tissue, wetland sedi-ment, microbial immobilization, and outfl ow water. This mass-balance model is used to determine the timing and impacts of STA maintenance practices.

Long-term phosphorus removal is achieved through the accumulation and burial of peat sediments [40]. Through burial, much of the phosphorus in the underlying peat deposits will be sequestered and functionally removed from the overlying water column. Sediment nutrient content and accumulation are currently being docu-mented using feldspar a white, crystalline mineral not found within the areas natu-ral sediments. Layers of feldspar are deposited in a small area of each test cell where, after settling, they create a distinct horizon layer [40]. Sediment cores are taken one year later and deposition rates are measured by the amount of sediment visible above the feldspar marker. The sediment profi le is divided and analyzed for total phosphorus content. Results of this analysis help to determine the rate of sedi-mentation and the mass of phosphorus retained in the sediment.



9 Water-quality improvements

In 1997, it was determined that numerous dairies have runoff total phosphorus con-centrations in excess of 1000 ppb, and that current monitoring data show some sites had concentrations above 7000 ppb [40]. Four basins in the Lake Okeechobee water-shed (approximately 115,000 ha) contribute the highest phosphorus concentrations and loads (35% of total) to the lake. All four basins contain active dairy operations. In 1997, the Florida Department of Environmental Protection enacted the Dairy Rule (chapter 62–670, Florida Administrative Code) that required that all dairies within the Lake Okeechobee watershed and its tributaries implement BMPs for the purpose of reducing phosphorus inputs into the lake. Under the rule, each farm was required to develop a site-specifi c plan providing for the collection, storage and dis-posal of wastewater. However, minimum on-site retention of water during a 25-year, 24-hour storm event was mandated. The general concept behind the Dairy Rule was to achieve a nutrient balance by retaining phosphorus on-site for uptake by forage crops, followed by harvesting of hay or other crops for cattle feed [39, 46]. Nondairy sources of phosphorus in the Lake Okeechobee watershed are primarily from beef-cattle pastures. Although animal densities and runoff phosphorus concentrations associated with beef-cattle pastures are relatively low, the large area (approximately 190,000 ha) of this land use makes them a major contributor of phosphorus.

The overall net phosphorus import in the northern Lake Okeechobee watershed was 1888 tons per year in 2002 which is a 28% decrease compared with data obtained in 1991 [40]. In 2005 the total phosphorus loading to the lake was approx-imately 600 metric tons per year, for a total reduction of 77% since 1991.

Agricultural BMPs reduced phosphorus concentrations leaving the EAA by 22% between 1996 (140 ppb) and 1999 (109 ppb) (STA1, Table 1). Infl ow rates into STA 1 increased after 1999 due to refl ux from sediment accumulation in the system. Other STAs (STAs 2 and 6, Table 1) indicate a further reduction in total phosphorus concentrations entering STAs from the EAA of 51% from levels in 1995. Infl ow concentrations entering these STAs are also increasing due to the same sediment phosphorus refl ux. Outfl ows from the STAs are less than 35 ppb, well below the original 100 ppb goal established in the EFA.

10 Impacts of tropical weather events on water quality

South Florida experienced an extremely rare occurrence with a series of hurricanes in 2004 and 2005. The region was hit by three major hurricanes and a remnant of a fourth in less than seven weeks in 2004, followed by a fi fth hurricane a year later. Collectively, the storms drove a cascade of water and nutrients across the region beginning in mid-August and lasting in many areas to the spring 2006. The Florida Department of Environmental Protection analyzed deviations from water-quality criteria for 2005 and reported that The Everglades water quality generally meets state numeric criteria, except total phosphorus (Table 2). Despite the 2004/2005 hurricane-related impacts, STA operations were able to reduce total phosphorus concentrations by 55 per cent during 2005. The operational STAs together treated



almost 1,850,000 million l of infl ow and removed 189 metric tons of total phos-phorus from surface water. Total phosphorus concentrations were reduced from an average infl ow of 179 ppb to and average outfl ow of 85 ppb. The Everglades marshes also generally showed little change in water quality from previous years despite the hurricanes in 2004 [40].

11 Future compliance

The Florida Department of Environmental protection proposed to set the fi rst numeric ambient water-quality standard for phosphorus in the Everglades at 10 ppb in 2002. The revised rule for the phosphorus criterion from 100 to 10 ppb received

Table 1: Average annual total phosphorus levels for storm-treatment areas (STA) in the Comprehensive Everglades Restoration Plan 1996–2005.

STA 1 STA 2 STA 5 STA 6 Year Infl ow Outfl ow Infl ow Outfl ow Infl ow Outfl ow Infl ow Outfl ow (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) (ppb)

1995 140 27 1996 112 28 1997 98 21 1998 122 22 56 171999 103 23 62 212000 147 31 71 162001 149 42 252 97 136 292002 148 44 78 16 251 83 68 172003 151 51 66 17 268 142 79 232004 145 47 75 14 254 98 54 122005 251 99 124 20 157 77 77 20

Table 2: Average total phosphorus levels and fl ow rates for storm-treatment areas (STA) in the Comprehensive Everglades Restoration Plan prior to and after hurricane events of 2004/2005.

January 2004 February 2006

Total phosphorus Total phosphorus

Infl ow Outfl ow Flow Infl ow Outfl ow FlowSTA (ppb) (ppb) (ft3 s–1) (ppb) (ppb) (ft3 s–1)

1 149 48 95 222 112 1532 79 15 456 118 51 5295 275 121 45 197 91 75



fi nal approval from the US Environmental Protection Agency in July 2005. To com-ply with the 10 ppb water-quality standard, The South Florida Water Management District has embarked on an ambitious research program for testing the feasibility of several advanced treatment technologies for the removal of phosphorus from waters leaving the STAs [40]. These technologies are being evaluated in pilot projects and are described below.

The fi rst treatment technology evaluated was the use of indigenous submerged plants to remove P from the water column followed by limerock fi ltration at the downstream end of the STA system. Removal of P is accomplished by plant uptake as well as by coprecipitation with calcium carbonate that precipitates from the water column due to photsynthesis-related pH elevations. The limerock fi lter further removes a small amount of particulate P and dissolved organic P. Another treatment alternative was the periphyton-based stormwater-treatment area takes advantage of natural processes to sequester phosphorus. Treated post-STA water fl ows over a substrate colonized with calcareous periphyton (attached submerged algae) and macrophytes (fl oating aquatic plants). The macrophytes function as additional substrate and a stabilizing mechanism for the algal mats. Phosphorus is removed form the water column through biological uptake, chemical adsorption, and algal mediated coprecipitation with calcium carbonate within the water column. The third technology is the low-intensity chemical dosing treatment method incorpo-rates small doses of aluminum salts directly into the STA infl uent. No apparent detrimental affect of Al accumulation has been noted at low dose rates. The chem-ical precipitation not only provides a mechanism for phosphorus removal and improved particulate removal, but also may enhance the phosphorus retention capacity of the sediments. No mechanical mixing or fl occulation is used. This low-tech approach uses the STAs to provide the biological treatment as well as fi ltration and setting of the precipitate.

12 Conclusions

The actions taken by the water-management district in South Florida have improved the water quality of the Okeechobee and Everglades watersheds. Phosphorus-source control programs mandated by the 1994 Everglades Forever Act reduced water total phosphorus concentrations below the required 100 ppb well ahead of the 2003 deadline, and are continuing to exceed expectations. The use of BMPs and STAs have prevented more than 2200 metric tons of phosphorus from entering the Everglades over the past nine years. BMPs continue to be an effective tool for reducing phosphorus at its source north of Lake Okeechobee and the EAA. In 2005, the EAA reported a 59 per cent total phosphorus load reduction with its BMP program marking a strong continued performance at reducing nutrient inputs to the Everglades. One agricultural production area, the C-139 basin, continued to be out of compliance in 2005, the third year of BMP program implementation. However, a reduction in total phosphorus concentrations was observed during the water year suggesting that the program is having positive effects and moving the basin toward compliance with regulatory requirements. Lowering water phosphorus



concentrations to 10 ppb established in 2005 will require the implementation of additional water-treatment measures.

The restoration of surface water fl ow in certain areas of the Okeechobee and Everglades watersheds have improved the surface-water fl ow and subsurface hydrology throughout both watersheds. Meanwhile, agricultural BMPs and water-treatment areas have improved water quality in these impacted watersheds. These restoration actions should reverse environmental impacts of increased P loading while maintaining the original goals of supporting agricultural production and urban development. The program of hydrological restoration and BMP imple-mentation created in response to Everglades Forever Act should be a model for similarly impacted costal-plain ecologies.

References

[1] Bancroft, G.T., Status and conservation of wading birds in the Everglades. American Birds, 43, pp. 1258–1265, 1989.

[2] Boodle, M.J., Ferreter, A.P. & Thayer, D.D., The biology, distribution, and ecological consequences of Melaleuca quinquenervia in the Everglades. Ev-erglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press, Delray Beach, FL, pp. 341–356, 1994.

[3] Browder, J.A., Relationship between pink shrimp production on the Tortugas grounds and water fl ow patterns in the Florida Everglades. Bulletin of Ma-rine Science, 37, pp. 839–56, 1985.

[4] Brown, M.J., Boundurant, J.A. & Brockway, C.E., Ponding surface drainage water for sediment and phosphorus removal. Transactions of the American Society of Agricultural Engineers, 24, pp.1478–1481, 1981.

[5] Brown, B., Weaver, J., Browder, J., Kitchens, W., Glaz, B., Armentano, T., Goodyear, C., Burns, L., Morrison, D., Thompson, N., Richards, P., Ogden, J.C., Hilton, R., Ambrose, R., Araujo, R., Barber, M.C., Bullock, R. & Loux, N., South Florida ecosystem restoration: scientifi c information needs. Science Subgroup. Management and Coordination Working Group, Inter-agency Task Force on the South Florida Ecosystem. South Florida Water Management District, West Palm Beach, FL, 1994.

[6] Daroub, S.H., Struck, J.D., Lang, T.A., Diaz, O.A. & Chen, M., Imple-mentation and verifi cation of BMPs for reduced P loading in the EAA. Final project report submitted to the Everglades Agricultural Area Environ-mental Protection District and The Florida Department of Environmental Protection. Tallahassee, FL, 2003.

[7] Davis, S.M., Phosphorus inputs and vegetation sensitivity in the Everglades. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis, & J.C. Ogden, St. Lucie Press, Delray Beach, FL, pp. 357–378, 1994.

[8] DeBush, W.F., Newman, S., & Reddy, K.R., Spatio-temperal patterns of soil phosphorus enrichment in Everglades water conservation area 2A. Journal of Environmental Quality, 30, pp.1438–1446, 2001.



[9] Diaz, O.A., Anderson, D.L. & Hanlon, E.A., Phosphorus mineralization from Histosols of the Everglades Agricultural Area. Soil Science, 56, pp. 178–185, 1993.

[10] Duever, M.J., Meeder, J.F., Meeder, L.C. & McCollom, J.M., The climate in South Florida and its role in shaping the Everglades ecosystem. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press: Delray Beach, FL, pp. 225–248, 1994.

[11] Fennema, R.J., Neidrauer, C.J., Johnson, R.A., MacVicar, T.K. & Perkins, W.A., A computer model to simulate natural Everglades hydrology. Ever-glades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press: Delray Beach, FL, pp. 249–289, 1994.

[12] Fisher, M.M. & Reddy, K.R., Phosphorus fl ux from wetland soils affected by long term nutrient loading. Journal of Environmental Quality, 30, pp. 261–271, 2001.

[13] Frohring, P.C., Voorhees, D.P. & Kushlan, J.A., History of wading bird popula-tions in the Florida Everglades: A lesson in the use of historical information. Waterbirds, 11, pp. 328–335, 1988.

[14] Harris, W.G., & Hollien, K.A., Changes across artifi cial E-Bh boundaries formed under simulated fl uctuating water tables. Soil Science Society of America Journal, 64, pp. 967–973, 2000.

[15] Gunderson, L.H., & Snyder, J.R., Fire patterns in the southern Everglades. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press, Delray Beach, FL, pp. 291–306, 1994.

[16] Holling, C.S., Gunderson, L.H., & Walter, C.J., The structure and dynam-ics of the Everglades system: Guidelines for ecosystem restoration. Ever-glades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press: Delray Beach, FL, pp. 741–756, 1994.

[17] Izuno, F.T., Sanchez, C.A., Coale, F.J., Bottcher, A.B. & Jones, D.B., Phos-phorus concentrations in drainage waters in the Everglades Agricultural Area. Journal of Environmental Quality, 20, pp. 608–619, 1991.

[18] Izuno, F.T., & Rice, R.W., Implementation and verifi cation of BMPs for reducing P loading in the EAA. Final project report submitted to The Florida Department of Environmental Protection and The Everglades Agricultural Area Environmental Protection District, Tallahassee, FL, 1999.

[19] Light, S.S., Wodraska, J.R. & Sabina, S., The southern Everglades: The evo-lution of water management. National Forum, 69, pp. 11–14, 1989.

[20] Light, S.S. & Dineen, J.W., Water control in the Everglades: A historical per-spective. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press, Delray Beach, FL, pp. 47–84, 1994.

[21] MacVicar, T.K., & Lin, S.T., Historical rainfall activity in central and south-ern Florida: Average, return period estimates and selected extremes. Environ-ments of South Florida: Present and Past II, ed. P.J. Gleason, Miami Geological Society, Coral Gables, FL, pp. 477–509, 1984.

[22] Maltby, E. & Dugan, P.J., Wetland ecosystem protection, management, and restoration: An international perspective. Everglades: The Ecosystem and Its



Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press, Delray Beach, FL, pp. 29–46, 1994.

[23] McIvor, C.C., Ley, J.A. & Bjork, R.D., Changes in freshwater infl ow from the Everglades to Florida Bay including effects on biota and biotic processes: A review. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden. St. Lucie Press, Delray Beach, FL, pp. 117–148, 1994.

[24] Morris, D.R. & Gilbert, R.A., Inventory, crop use and soil subsidence in Florida. Journal of Food, Agriculture & Environment, 3, pp. 190–193, 2005.

[25] Morris, D.R., Glaz, B. & Daroub, S.H., Organic matter oxidation poten-tial determination in a periodically fl ooded Histosol under sugarcane. Soil Science Society of America Journal, 68, pp. 994–1001, 2004.

[26] National Agricultural Statistics Service (NASS), Florida Agricultural Com-modity Statistics, Washington, DC, 2005.

[27] Newman, S., Grace, J.B., & Koebel, J.W., Effects of nutrients and hydrope-riod on Typha, Cladium and Eleocharis: Implications for Everglades restora-tion. Applied Ecology. 6(3), pp. 774–783, 1996.

[28] Nue, G.B., Childers, D.L. & Jones, R.D., Phosphorus biochemistry and impact of Phosphorus enrichment: why is the Everglades so unique? Biosystems, 4, pp. 603–624, 2001.

[29] Ogden, J.C., Recent population trends of colonial wading birds on the Atlantic and Gulf coastal plains. Wading Birds, eds. A. Sprunt IV, J.C. Ogden & S. Winckler, New York, NY, pp. 137–153, 1978.

[30] Ogden, J.C., A comparison of wading bird nesting colony dynamics (1931–1946 and 1974–1989) as an indication of ecosystem conditions in the southern Ever-glades. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press: Delray Beach, FL, pp. 533–570, 1994.

[31] Robbins, C.W. & Carter, D.L., Conservation of sediment in irrigation runoff. Journal of Soil Water Conservation, 30, pp. 134–135, 1975.

[32] Robertson, W.B. & Kushlan, J.A., The South Florida fauna. Environments of South Florida: Present and past, memoir No. 2., ed. P.J. Gleason, Miami Geological Society, Coral Gables, FL, pp. 414–452. 1974.

[33] Robertson, W.B. & Frederick, P.C., The faunal chapters: Contexts, synthe-sis, and departures. Everglades: The Ecosystem and Its Restoration, eds S.M. Davis & J.C. Ogden, St. Lucie Press: Delray Beach, FL, pp. 709–37, 1994.

[34] Ross, M.R., O’Brien, J.J. & Flynn, L.J., Ecological site classifi cation of Flor-ida Keys terrestrial ecosystems. Biotropica, 24, pp. 488–502, 1992.

[35] Schuman, G.E., Spomer, R.G. & Priest, R.F., Phosphorus losses from four agricultural watersheds on Missouri Valley loess. Soil Science Society of America Journal, 37, pp. 424–427, 1973.

[36] Sharpley, A.N., Daniel, T.C. & Edwards, D.R., Phosphorus movement in the landscape. Journal of Production Agriculture, 6, pp.492–500, 1993.

[37] Shih, S.F., Glaz, B. & Barnes, Jr. R.E., Subsidence of organic soils in the Everglades Agricultural Area during the past 19 years. Soil and Crop Science Society of Florida Proceedings, 57, pp. 20–29, 1998.



[38] Sievers, P., Pescatore, D., Daroub, S., Stuck, J.D., Vega, J., McGinnes, P. & Van Horn, S., Performance and optimization of agricultural best management practices. Everglades BMP program annual report, South Florida Water Man-agement District, West Palm Beach, FL, 2003.

[39] South Florida Water Management District (SFWMD), Lower East Coast Re-gional Water Supply Plan, West Palm Beach, FL, 1994.

[40] South Florida Water Management District (SFWMD), Comprehensive Everglades Restoration Plan, 2005 Report to Congress, West Palm Beach, FL, 2005.

[41] Stuck, J.D., Izuno, F.T., Campbell, K.L., Bottcher, A.B. & Rice, R.W., Farm-level studies of particulate phosphorus transport in the Everglades Agricul-tural Area. Transactions of the American Society of Agricultural Engineers, 44, pp. 1105–1116, 2001.

[42] Terry, R.E., Nitrogen mineralization in Florida Histosols. Soil Science Soci-ety of America Journal, 44, pp. 747–750, 1980.

[43] Thomas, T.M., A detailed analysis of climatological and hydrological records of South Florida with reference to man’s infl uence upon ecosystem evolution. Environments of South Florida: Present and past, memoir No. 2., ed. P.J. Gleason. Miami Geological Society, Coral Gables, FL, pp, 82–122, 1974.

[44] Tomlinson, P.B., The Biology of Trees Native to Tropical Florida. Harvard: Harvard University Printing Offi ce: Boston, MA, 1980.

[45] Qualls, R.G. & Richardson, C.S., Phosphorus enrichment affects: Litter de-composition, immobilization, and soil microbial phosphorus in wetland me-socosms. Soil Science Society of America Journal, 64, pp. 799–808, 2000.

[46] US Army Corps of Engineers (USCOE), Comprehensive Review Study. Central and Southern Florida Project, Jacksonville, FL, 1994.

[47] US Census Report (USCR), Florida Population Statistics, Washington, DC, 2002.

[48] Vaithiyanathan, P. & Richardson, C.J., Macrophyle species changes in the Everglades: Examination along a eutrophication gradient. Journal of Envi-ronmental Quality, 28(4), pp. 1347–1358, 1999.

[49] Walters, C., Gunderson, L. & Holling, C.S., Experimental policies for water management in the Everglades. Applied Ecology, 2, pp. 189–202, 1992.

[50] Weaver, J. & Brown, B., Federal Objectives for the South Florida Restoration. Science Sub-Group, South Florida Management and Coordination Working Group. US Department of Interior, Washington, DC, 1993.


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