The Merced River is a 145-mile-long tributary flowing from the high peaks of the Sierra Nevada mountain range into the Central Valley of California. It is the primary watercourse that carves through the southern section of Yosemite National Park. Beginning as snowmelt, the river experiences a steep gradient change as it descends from the alpine wilderness to the flat agricultural plains. This journey establishes a major watershed that supplies water for agriculture and sustains a diverse ecosystem before merging with a larger regional system.
Defining the Headwaters
The precise origin of the Merced River is found deep within the High Sierra, in the southeastern corner of Yosemite National Park. The river’s main stem begins near the Clark Range at the confluence of the Merced Peak Fork and the Triple Peak Fork. This alpine environment is situated at an elevation of approximately 8,017 feet above sea level. The initial flow is fed primarily by snowmelt and small alpine lakes draining from the high country. This high-altitude source defines the river’s character as pristine, cold, and fast-moving.
The Passage Through Yosemite and the Foothills
From its headwaters, the river flows north and west, quickly descending through steep, glaciated canyons. It accumulates water from tributaries like Illilouette Creek and the South Fork Merced River. Entering Little Yosemite Valley, the river plunges over the Giant Staircase, which includes the iconic Nevada Falls and Vernal Falls.
Upon reaching the Yosemite Valley floor, the river’s gradient lessens, allowing it to meander through the broad meadow habitat. The river then narrows, entering the steep Merced River Canyon west of the valley near El Portal. This gorge maintains its “Wild and Scenic” designation as the river continues its fast descent.
The river’s character changes substantially as it exits the granite canyon and enters the lower foothills, transitioning to a managed water resource. The flow is impounded by the New Exchequer Dam to form Lake McClure, which regulates water for power generation and irrigation. Below this main dam, the river passes through additional control structures, including the McSwain and Crocker-Huffman Dams, before emerging onto the flat terrain of the Central Valley.
The Confluence in the Central Valley
After traversing the foothills, the Merced River enters the expansive agricultural region known as the San Joaquin Valley. Here, the river becomes a slow-moving, meandering stream, characterized by a low elevation and a heavily utilized water supply. The river completes its journey by joining a much larger river system.
The Merced River ultimately terminates by merging with the San Joaquin River. This confluence point is located at Hills Ferry, situated a few miles south of the city of Turlock, in Stanislaus County. At this terminal point, the river’s elevation is a mere 56 feet above sea level.
The river’s flow in this final stretch is often significantly diminished due to extensive water diversion for agricultural irrigation across Merced County. This reliance on the river has necessitated the establishment of facilities like the Merced River Hatchery to support the local fall-run Chinook salmon population. The Merced River’s contribution is a significant point for the San Joaquin River, which is often dry upstream of this major tributary.