 Many small diversion dams block the Merced River downstream , many of which were built by the Merced Irrigation District to supply water to farms in the Central Valley . The lowermost , the Crocker @-@ Huffman Diversion Dam , was built just before 1907 , and completely blocks the passage of anadromous fish up the Merced River . McSwain Dam , the other major lower dam , also serves as a forebay ( regulating dam ) for New Exchequer Dam . Aside from controlling flows in the lower river the dam also produces some hydroelectricity . Because of the nearly desiccated flow of the river as it nears the mouth , like most other rivers in the San Joaquin Valley , little water in the Merced River actually reaches the Pacific Ocean . 
