The Ross Barnett Reservoir (also known as "The Rez") is an impoundment of the Pearl River between Madison and Rankin Counties in the U.S. state of Mississippi. The 33,000-acre (130 km²) lake serves as the state's largest drinking water resource, and is managed by the Pearl River Valley Water Supply District. The lake features 105 miles (169 km) of shoreline impounded on the south by a 3.5-mile (5.6 km) man-made dam and spillway.