The Alafia River is 25 miles (40 km) long, with a watershed of 335 square miles (870 km2) in Hillsborough County, Florida, United States, flowing into Tampa Bay. The watershed contains ten named lakes and ponds, and 29 named rivers, streams and canals. During the rainy season, excess water is pumped to the new C.W. Bill Young Regional Reservoir, which opened in 2005. The river begins North of Mulberry, then splits in Lithia, with one branch flowing east into Hillsborough Bay at Riverview, and the other south to Tampa Bay.