Tarrant Regional Water District (TRWD) was the first partner that developed cooperative agreements and a memorandum of understanding to assess their watersheds. As a raw water provider to the metropolitan area around Fort Worth, they were concerned with sediment accumulation in their reservoirs along with maintaining good water quality. TRWD owns and/or manages five major reservoirs supplying water to Fort Worth and several other Metroplex communities and industries. The watersheds are within the Upper Trinity River Basin and encompass all or portions of 19 counties. The reservoirs control runoff from 14,800 sq. km (5,700 sq. mile) and serve a population of 1.5 million people with municipal, industrial, and recreational water. The reservoirs include Lake Bridgeport, Eagle Mountain Lake, Lake Benbrook, Richland-Chambers Lake, and Cedar Creek Lake.
TRWD databases and those of other state and federal agencies were used to calibrate and validate the computer models. These databases include measured flow and sediment into their reservoirs. More recently, they have done extensive sampling of streamflow and reservoirs to collect nutrient and chemical constituents for calibrating the models. Scientists have added instream kinetics to SWAT (similar to those included in the EPA model QUAL 2E) to simulate the effects of nonpoint source (NPS) constituents moving through the tributary or stream network.
The partners have developed an interface between the SWAT model and the EPA reservoir model Water Quality Analysis Simulation Program (WASP4) in order to evaluate effects of BMPs in the watershed on water stored in the reservoir.