 The headwaters of the Merced River are at 8 @,@ 017 feet ( 2 @,@ 444 m ) at the foot of the Clark Range , a subrange of the Sierra Nevada , rising at the confluence of the Triple Peak Fork and Merced Peak Fork after they cascade down glacially polished slopes from the high country in the southeastern corner of Yosemite National Park. the Merced River flows for 145 miles ( 233 km ) westward through a series of canyons , gorges and finally the flat plains of the Central Valley . From its headwaters , the river flows north for a short distance and collects the Lyell Peak Fork . The course of the Merced then turns to the north west and flows through a steep walled canyon for 2 @.@ 5 miles ( 4 @.@ 0 km ) where the river receives the Red Peak Fork and then collects into Washburn Lake at 7 @,@ 612 feet ( 2 @,@ 320 m ) elevation . The Merced continues to the northwest for 3 miles ( 4 @.@ 8 km ) where collects into Merced Lake . Leaving Merced Lake , the river continues to the west northwest for 2 @.@ 3 miles ( 3 @.@ 7 km ) where the canyons open up into Echo Valley . The river then turns generally westward for another 3 miles ( 4 @.@ 8 km ) , where it snakes through a spectacular narrow gorge between massive , glacially resistant granite cliffs . The gorge opens up after Bunnell Point and Sugarloaf Dome confine the river to form Bunnell Cascade , before turning southward through the Lost Valley of the Merced , and then spills over an unnamed granite cascade into Little Yosemite Valley , a glacial valley that sits 2 @,@ 000 feet ( 610 m ) feet above the more famous Yosemite Valley at approximately 2 / 3 scale . The Merced River then drops over Nevada Falls and Vernal Falls , receives Illilouette Creek , and passes into the main Yosemite Valley , where it meanders between pine forests that fill the valley floor . 
