California Water Science Center
Surface Water - Cycle II
Merced River at River Road Bridge near Newman, CA (11273500)
The Merced River is located in a large basin on the east side of the San Joaquin Basin. A large reservoir in the basin stores clean water from the Sierra Nevada; water released from this reservoir is used for agriculture and hydropower, and to assist the migration of salmon and steelhead. Streamflow below the reservoir is supplemented by storm runoff in the winter and irrigation return flows during the spring and summer. About 56 percent of the basin below the resevoir is agricultural, thus water quality of the Merced River is a valuable indicator of the impacts of agriculture on water quality in east side tributaries to the San Joaquin River.
The Merced River is being sampled for water-borne constituents and biological characteristics as part of the Trend Network for Streams. Water, fish and streambed sediment were also sampled for mercury and methylmercury in the summer of 2002 as part of the Status Assessment for Mercury.