Natural Areas Locator

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San Francisco Recreatioin & Park's Description of Capital Plan Format Changes (PDF 84 KB)

Natural Areas

Lake Merced

Location: John Muir Drive, Skyline Boulevard, and Lake Merced Boulevard
Established: 1930
Size: Park: 614.0 acres (including water)/Natural Area: 395.0 acres
Park Type: Dunes/Wetland

Lake Merced, a freshwater lake in the southwest corner of San Francisco, is a major water, recreational, and natural resource for the City and County of San Francisco and the surrounding area. It is also an important stop for migratory birds on the Pacific Flyway. More than 250 species of birds can be seen throughout San Francisco during the year, most of which migrate from as far as South America to the Arctic and back. Many of these migrating birds stop only briefly at Lake Merced to feed and rest as they continue their journey to the north or south; others mate, build nests, and nurture a new generation of young birds in San Francisco before returning to their wintering grounds elsewhere.

The Water

At the end of the last ice age, beginning some 15,000 years ago, the ocean flooded into the mouth of the Merced Valley, creating an inlet. The sand-laden ocean current moved across the mouth of the flooded valley, depositing its load as a sand bar across the inlet and damming off Lake Merced. Inputs from freshwater springs and creeks made the lake's water less and less saline. On rare occasions such as an extreme high tide, heavy flooding or earthquakes, water from the north lake would move through a gap in the dunes and meet the Pacific Ocean only 50 yards away.

On November 22, 1852, a tremor shook the area, breaching the sand bar, and dropping the lake level by 30 feet. The inlet was dammed in the 1880s in order to expand Skyline Boulevard and the Great Highway. The lake was later divided into four distinct lakes: East Lake, North Lake, South Lake, and Impound Lake.

Beginning in the 1870s, the Spring Valley Water Company sold Lake Merced water to San Francisco residents. When the Hetch Hetchy water supply system was completed in 1934, use of the lake as a domestic water source was discontinued, although today it is considered an emergency water supply.

Bank Swallows

The Golden Gate Audubon Society has observed more than 50 species of birds breeding and nesting at Lake Merced. The bank swallow, a state-listed threatened species, arrives here every spring to nest in the vicinity. Bank swallows, which winter in South America and breed throughout North America, are small, brown-backed birds with an irregular fluttery flight pattern, a notched tail, and a distinctive dark breast band. Bank swallows build their nests in the banks and cliffs along the beach near Fort Funston, at the end of a three-foot-deep tunnel, to protect their young from the wind and rain.