WAM has been applied to the Lake Okeechobee Protection Plan (LOPP) area in numerous studies over the past several years. These previous studies have been related to either the Comprehensive Everglades Restoration Plan (CERP) performed for the SFWMD and the US Army Corps of Engineers (USACE), or phosphorus budget analysis conducted for SFWMD. The most recent project completed on the LOPP, was the WAM Enhancement and Application on Lake Okeechobee watershed (WAMEA). WAMEA (Phase III) was completed in March 2009. The goal of the WAMEA was to develop an assessment tool that will enable the evaluation of ongoing and proposed phosphorus control measures at the Lake Okeechobee Watershed scale. The assessment tool will enable the District to refine prior Technical Plans for the Lake Okeechobee Construction Project and adapt it to better meet the Total Maximum Daily Load (TMDL) goal of 140 metric tons of phosphorus per year.
|
|
Baseline simulations for each basin in the WAM Enhancement study area were performed to represent existing conditions. The existing conditions were based on mapped land uses. Each land use was assigned parameters to represent current fertilization and water management practices that affect water quality. Then "what-if" scenarios were run, where the land use was updated to included various BMP implementations, and the modeled results used to evaluate the most effect method to reduce the P loading in the watershed.
WAM has been used extensively in the Lake Okeechobee area, with varying goals and objectives. Details of each of these projects are described in the relevant projects below.
|
|
The objective of this project was to develop specific criteria to determine the relative impacts of land use, soils, hydrography, and other parameters on the discharge water quality, wetland value, and flood impact in the St. Johns River Basin. This project was the first fully daily routing option of WAM completed in 1998. The purpose of the SJRWMD project was to extend the GIS based watershed model development effort to unmodeled subbasins in the Lower St. Johns River Basin that are identified as major contributors of pollutant loading to the mainstem. Three major subbasins that were covered in this project:
(1) Black Creek subbasin;
(2) Julington Creek subbasin; and
(3) OrtegaRiver subbasin.
|
|
|
WAM was calibrated on the Black Creek subbasin and validated on the other two basins in order to access the ability of WAM to simulate pollutant loadings on ungauged basins, which is a major issue in this region. WAM utilizes process-based models in its simulations in order to minimize calibration data requirements and to enhance the development of management alternatives. This project demonstrated WAM's ability to accurately simulate ungauged basins. Several additional scenarios runs for BMP and regional retention projects has subsequently done to assist the District with their Lower St. Johns River PLRGs evaluation and implementation programs.
|
|
|
On March 22, 1995 the Suwannee River Water Management District (SRWMD) authorized Soil and Water Engineering Technology, Inc. (SWET) to perform a watershed assessment with respect to water quality for the entire District by using a Geographic Information System (GIS). The outcome of this project is the SRWMD Water Assessment Model (SR-WAM), which became known as WAMview as it was designed as an extension to ESRI ArcVIEW 3.2.
The watershed assessment approach for the SRWMD used the District's GIS databases (land use, soils, hydrography, etc.) in addition to known pollutant transport processes to locate the areas within the District that have potential adverse impacts on the environment. The goal is to locate the problem areas and to quantify the relative impact on different scales in the study area.
Two methods or sets of watershed assessment algorithms were developed as part of this project. The first method provides spatial assessment using impact indices while the second method utilizes hydrologic and contaminant transport modeling. The method used depends on the watershed assessment parameter of interest. The assessment parameters evaluated were water quantity, nitrogen, phosphorus, total suspended solids or sediment, biological oxygen demand (BOD), coliform bacteria, toxic materials, wetland habitat value, wetland value for water quality treatment, and potential flood proneness. Two approaches for estimating the environmental impact were used, depending on the parameter being assessed. An indexing approach was utilized for the following assessment parameters: BOD, coliform bacteria, toxic or hazardous materials, wetland habitat value, and wetland value for water quality treatment. A modeling approach is used for water discharge, flood proneness, and nitrogen, phosphorus, and sediment loads. The indexing approach is used for assessment parameters (BOD, coliform bacteria, and toxins) that are hard to quantify or are not directly associated with pollutant transport, while the modeling approach addresses the major pollutants of sediment and nutrients. Both approaches provide the overall basin impact.
|
|
Nitrogen continues to be of concern in the Suwannee River Water Management District. In order to address these concerns, a partnership with the agricultural community was developed with the Florida Department of Agriculture (FDACS), the SRWMD, the USDA-Natural Resources Conservation Service (NRCS), the Florida Department of Environmental Protection (FDEP), the Soil and Water Conservation Districts and other partners within the watershed. This partnership has concluded that the creation and implementation of BMPs is the best approach to control nitrogen levels in the District‘s ground and surface water.
Both the partnership, in general, and FDEP, in particular, had a strong interest in determining the potential impacts of BMPs. In order to address this issue, FDACS contracted with SWET to use WAM to evaluate the impacts of key agricultural BMPs to be implemented in the basin by 2008. The Lower Suwannee River Basin was chosen for these analyses because it contains a high density of agricultural land uses.
The Suwannee Basin was selected as a focus basin for a joint project with the NASA COAST Interface to develop an on-line tool to test BMP's. This project is currently under development.
|
|
SWET contracted with the National Institute of Water & Atmospheric Research Ltd (NIWA) in New Zealand to do a comprehensive watershed assessment of a large basin targeted for development just north of Auckland. The purpose of the assessment was to develop a plan for acceptable levels of development that would not adversely impact the streams and downstream estuary. A variety of scenarios were run to evaluate impacts during both construction and post construction phases.
The study clearly showed that the amount of construction within the basin had to be regulated to prevent significant impacts; however, over time, the basin could be developed if done properly with critical areas protected.
|
|
The Florida Watershed Restoration Act and Federal TMDL program requires the development of TMDLs for pollutants that result in non-attainment of water quality standards, allocation of those loads among point and nonpoint sources, and implementation to achieve water quality standards. WAM has been applied by the St. Johns River Water Management District (WMD), Suwannee River WMD and South Florida WMD to assist in the development of pollutant load reduction goals (PLRGs). Also, the U.S. Environmental Protection Agency has used this model for a TMDL project in the Myakka River Basin, Florida.
The Myakka River is a diverse dark water river approximately 60 miles in length just off the gulf coast of southwest Florida. Due to strong citizen interest in preservation of its pristine nature and scenic qualities, the Myakka was declared a 'Wild and Scenic River' by the Florida State Legislature in 1985. The eastward development fringes of Venice and other coastal cities in the region are increasing their adverse impact on the lower reaches of the river. The middle and upper subbasins have a significant amount of mining and agricultural activities including phosphate mining, cattle, citrus, and vegetables. The Myakka River State Park encompasses a significant portion of the middle section of the river basin including the Upper and Lower Myakka Lakes.
|
|
|
The USEPA, in cooperation with various state and local agencies and interest groups, is in the process of developing Total Maximum Daily Loads (TMDLs) for various listed reaches within the Myakka River Basin. The TMDL process has three important aspects: first, determine and set the appropriate TMDLs for the listed reaches; second, to develop specific abatement plans for achieving the TMDL; and finally, to implement and monitor the plans that will reduce non-point source pollution loads.
|
To assist EPA in these efforts, WAM was applied to the watershed. The model assisted in: (1) assessing and evaluating environmental impacts resulting from point and non-point source runoff; (2) developing management strategies for controlling runoff, pollution loading, and associated environmental problems; and (3) evaluating environmental impacts resulting from proposed management strategies. For this project, WAM was enhanced to simulate biological oxygen demand (BOD) as well as water control structures (culverts and weirs) found in the basin. The simulated values provided a good representation of observed data.
|
|
For the Hillsborough River project WAM was linked to WASP to provide simulation data to develop additional TMDL's in the Florida. Read the project section on this below.
|
|
In support of the FDEP TMDL program, SWET has calibrated WAM for use with WASP modeling to provide daily estimated flows, water levels, total suspended solids, nutrients (nitrogen and phosphorus species), BOD, chlorophyll a, and dissolved oxygen levels. To develop the TMDL limits, SWET used the Watershed Assessment Model (WAM) to simulate the source loads of pollutants and water quantity originating on the land surrounding the three water bodies that drain to the WBIDs of concern. WAM has been linked to the Water Quality Analysis Simulation Program (WASP). The source load generated by WAM was used as the input parameters to WASP in order to accurately model the lake simulation processes present.
|
|
The purpose of this project is to simulate water quantity and quality discharges within the Lake Hancock Basin in support of the Florida Department of Environmental Protection’s (FDEP’s) TMDL Program. The basin is located in the Lakeland, FL area and drains into the Peace River. The WAM model was used to simulate the hydrology and pollutant contributions to the entire stream system. This basin is dominated with natural and manmade (phosphate mining pits) lakes, which have been listed for poor water quality by FDEP. WAM simulated constituent movement throughout the stream system, however, to represent more detailed in-lake processses, it was linked to the BathTub lake model. WAM produced all of the necessary inflow and outflow quantities and water qualities for the BathTub model. The model was modified during this project to handle the significant lake leakage that occurs in this basin
|
|
In order to provide information to support the identification of planning targets for total phosphorus (TP) concentrations and loads in Fisheating Creek (FEC), a pre-drainage simulation was performed using WAM. The pre-drainage hydrographic network was mapped using historical aerials. The historic land use was mapped by an interpolation technique based on native landuse occurence on soil types in the basin. The results of this analysis are shown below.
To determine the assimilative capacity of wetland and streams systems under native conditions, a literature/data search was done to locate information that would be relevant to native TP concentrations in FEC. Based on the data collected and discussions with the experts, it is our best professional judgment that the most probable annual average pre-drainage/native TP concentrations would have been around 70 to 80 ppb. However, given the uncertainty in the estimates, there is a significant error range around this estimate that could range somewhere between 30 and 100 ppb. Given these annual average values, it should be recognized that daily variations in TP concentrations could be expected to range between 20 and 250 ppb.The above ranges were used as targets for the re-calibration of WAM for the pre-drainage condition.
This technique was also used in the TMDL assessment done for the 3 lakes in the Upper Peace River.
|
|
WAM has been used to test the conceptual design of Reservoirs and Regional Storm Wastewater Treatment Systems. The DMSTA submodel for STAs,developed by Bill Walker, was integrated into WAM for this project. The project included the testing of different scenarios with the placement or design of the systems. By simulating these different scenarios the expected nutrient reduction can be compared, allowing for a relative comparisons to be made before the expensive process of construction and implementation in considered.
|
 
|
|
WAM has been selected for Springshed assessment projects because of its capability to simulate surface and groundwater flow and water quality, including land source loads and appropriate attenuation processes along the flow path. This includes its ability to handle closed (no surface outlet) sub-basins and their resulting groundwater flow and nutrients. Below are two projects in which WAM has been effectively used in this capacity:
Rainbows Springs
The purpose of this project was to develop and utilize a GIS-based computer model to simulate water and non-point source pollution discharges from Rainbow Springs and to spatially quantify sources of nitrogen; the pollution of greatest concern. Located several miles north of the City of Dunnellon in western Marion County, Florida, Rainbow Springs is one of the largest spring systems in the state, and is the dominant source of water in the Rainbow River, which flows into the Withlacoochee River near the southern edge of Dunnellon.
There were three land use scenarios developed and simulated using the Watershed Assessment Model (WAM). The first is the “base” or “existing condition” run that is based on the 2007 land use coverage. The 2007 land use is primarily based on 2005 land use data updated to reflect 2007 tax assessment data and aerial verification. The next two scenarios use the “2025” and “2055” future land use coverages. The future land use scenarios required the development of a future condition utility zone (central sewer).
The figure below provides the predicted trends that are anticipated to occur as the springshed develops. The red trend line shows the current nitrogen trend in the springs based on measured data, while the blue trend line indicates what would happen if 2007 land use within the springshed were never altered. The green trend line shows the anticipated nitrogen increases in the springs based on predicted future land use. The nitrogen levels in the springs are likely to reach about 5 to 6 ppm by 2055, as compared to about 1.7 ppm currently observed in the Rainbow River.
|
Coastal Springs
The purpose of this project is to simulate water quantity and quality discharges for the coastal springs along the west coast of Florida from Pasco County up to Crystal River. This project was completed for the Southwest Florida Water Management District to determine the regional growth impacts on the numerous springs along the coast. The Springs Coast watershed encompasses approximately 800 square miles of coastal Citrus, Hernando, and Pasco counties in west-central Florida. The watershed includes four major spring groups, discharging an estimated 900 million gallons per day from the Floridan aquifer into the Crystal, Homosassa, Chassahowitzka, and Weeki Wachee rivers (Figure 1). Additionally, there are numerous second and third magnitude springs within the study area. Most of these springs lie west of the U.S. Highway 19 corridor. This area has undergone, and continues to undergo, considerable development. This development has impacted and will continue to impact, the springs in the Springs Coast Basin. Nitrate is the primary constituent of concern. The model was used to assess three scenarios including predevelopment, existing condition, and complete buildout.
This involved the compilation of existing data on the locations, and groundwater basins of the springs in the Coastal Rivers Basin, and the development of new information on the spatial extent of the surface water contributing area of each spring(s) complex. This effort produced: maps of the locations of springs and surface and ground water contributing areas, a Geographic Information System (GIS) database, and pollutant loading estimates and predictions linked to land use within the surface water contributing areas.
|
|
|
|
