 Tenaya , Yosemite , Bridalveil and Pigeon Creeks join the Merced before it breaches the glacial moraine at the valley 's end . From there the river picks up Cascade Creek and turns south near El Portal , flowing through Merced River Canyon . State Route 140 follows the river out of the west entrance to the national park , a few miles before the South Fork Merced River , the largest tributary , joins from the left . The river arcs northwest to receive the North Fork , and a few miles after it enters Lake McClure , formed by New Exchequer Dam . Below New Exchequer , the river flows west through a heavily irrigated region of the Central Valley , passing through McSwain and Crocker @-@ Huffman Dams and the cities of Hopeton , Delhi and Livingston . It joins the San Joaquin River at Hills Ferry , a few miles south of Turlock . 
