Agricultural runoff impacts on total maximum daily loads and water quality
Escambia River Drainage Characterization.
This research component will consist of a compilation of land use data and nutrient loading data that will be integrated into a GIS database. Much of these data are currently available from the NWFWMD and from DEP; both agencies will provide the support of their datasets (see appended letters).
Site Description. The Escambia River represents the largest freshwater flow into the Pensacola Bay system. In Florida, the Escambia River divides Escambia and Santa Rosa Counties. Major drainage tributaries of this river in the State of Florida are listed by county:
Escambia County (South to North) Santa Rosa County (South to North) The watershed includes industrial, residential, unmanaged forestland, active silviculture, pastured and active tillage agricultural areas. Total nitrogen content of the river as it approaches Escambia Bay estuary ranges from 0.45 to 0.71 ppm, with a state guideline limit is 0.36 ppm (www.dep.state.fl.us/ nwd/ecosys/waterquality/pensacolabay.htm). The river has been targeted by DEP for reductions in nitrogen and phosphorous loads from both point and nonpoint sources. Reductions in total nitrogen have been apparent from the move to upland disposal of an industrial point source, and agricultural runoff is coming under increasing scrutiny for degradation of tributaries and the river itself (Ray, 2000a, 2000b). The NWFWMD will provide pollutant load and flow and stage data from two stations on the Escambia River. These data are being collected as a part of the NWFWMD project to identify pollutant loads on tributaries of the Pensacola Bay system. The Escambia River stations are located near Century and Molino. For comparison purposes the NWFWMD will also provide baseline water quality and flow data, as well as data from two stations each on the Shoal and Yellow Rivers and one station on the Blackwater River. Data analyzed will include various forms of nitrogen and phosphorus, metals, total suspended solids, and field parameters. Additionally, ongoing collection of water quality data on the Escambia River by the DEP is available to the project. Previous work on agricultural impacts on the drainage streams to the Escambia River has highlighted the role of sedimentation from erosion and nutrient additions. As this database builds, we will take additional samples for water-quality analysis in the Escambia River drainage basin, particular in the outfalls from the Tate High School study sites and in drainage areas of the aquaculture BMP demonstration site. Analysis of Nutrient Loadings to the Escambia River. This project will initiate a quarterly sampling of the major sub-drainages (see above) into the Escambia River. Temperature, pH, oxygen concentration, and conductivity will be measured at each site. Samples will be returned to the lab and analyzed for nutrients (N and P), suspended sediment, and total organic carbon. Concurrently, the land use/land cover will be determined for the drainage basins of the tributaries from digital maps available from the Florida DEP. In a GIS database we will determine the percentage land use as industrial, residential, unmanaged forest, silviculture, and agriculture. Sampling on a fixed quarterly schedule may miss storm event related loadings, but chronic problem areas should be identifiable. Additionally, data (and students) will be exchanged with Dr. John McCall of the University of West Alabama (see attached letter), who is initiating water quality monitoring in the Alabama portion of the Escambia River Basin.
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