Joe Pool Lake is mostly fed by Mountain Creek and Walnut Creek and drains north into Mountain Creek leading into Mountain Creek Lake. Joe Pool Lake is one of the only lakes in Texas that actually drains to the north. Joe Pool lake impounds water in two arms formed by Mountain Creek and Walnut Creek. The Mountain Creek Water Shed is in the Upper Trinity River Basin and has a length of 37 miles and a total drainage area of 304 square miles. There are 64 miles of shoreline at normal conservation pool of 522 feet mean sea level (msl). Impoundment began in January 1986. Trees and fences were cleared between 501 msl and 522 msl in the main body of the lake. However in the upper branches of the lake, the trees were left for fish habitat.
Currently Joe Pool Lake serves as a reservoir for the City of Midlothian for their public water supply. Several other entities have water interests in Joe Pool Lake, but are not currently using the water resources. The City of Midlothian has a water intake structure in the southeast leg of the lake. They pull anywhere from 1.0 million gallons per day of water in the winter months to 9.0 million gallons per day in the summer months. The Trinity River Authority of Texas also has a water intake structure in Cedar Hill State Park, but it currently not in use.