The South Concho River is one of the few rivers in Texas to run south to north for its entire length. Rising from Anson Springs some 4 miles (6.4 km) south of Christoval, Texas, in Tom Green County, it flows north through the town of Christoval, then continues north for 13 miles (21 km) before it joins the Middle Concho to form Twin Buttes Reservoir in what is now southwest San Angelo. When released, the river flows through Lake Nasworthy, and continues north to join the North Concho River at Bell St. in east San Angelo. The river is known for its cool, clear, deep water and its pecan-covered banks. Watercress grows in the shallows along the banks.