Lobos Creek is a stream in the Presidio of San Francisco, draining urban runoff and underground springs and flowing intermittently west for 1 mile (1.6 km) from near Mountain Lake to the Pacific Ocean between Baker Beach and China Beach, about 5 miles (8 km) west of downtown San Francisco and at Sea Cliff, California. Groundwater aquifers beneath Mountain Lake feed the creek. Its name derives from the Spanish ‘lobo marino‘ (sea wolf), a reference to the sea lion. It is the city’s only remaining above‐ground stream. The San Francisco Peninsula once boasted numerous creeks with diverse riparian habitats. Creeks such as Hayes, Yosemite, Mission, Dolores, Eire, Precica, and Trocadero have since been filled in, paved over, or diverted into storm drains. Only a portion of Islais Creek remains, while most of Lobos Creek survives—albeit extensively modified. In 1776, Spanish explorer Juan Bautista de Anza ended his second northward expedition at Mountain Lake, camping for two days and selecting a site for a presidio. The Presidio of San Francisco—originally El Presidio Real de San Francisco—is a former US Army fort at the northern tip of the San Francisco Peninsula in the Golden Gate National Recreation Area. Fortified on September 17, 1776, by New Spain to secure a foothold in Alta California and San Francisco Bay, it passed to Mexico in 1810 after the Mexican War of Independence and to the United States after the Mexican-American War in 1848. Following California’s statehood in 1850, American settlers established ranches, farms, and dairies near freshwater sources. In the early 1850s, John H. Baker owned extensive land near Lobos Creek and set up a dairy, Golden Gate Ranch (or Baker’s Ranch), at present-day Baker Beach. On his death in 1863, his widow, Maria Baker, secured title and later mortgaged the land to John Brickell. When Baker foreclosed on the loan, Brickell secured possession of the land; however, since it was unclear where the exact property lines of Baker’s Ranch were located, a court case ruled that the federal government owned the north bank of the creek and half ownership of the water rights.

In 1857, San Francisco needed a more dependable freshwater supply. Franchised by the San Francisco City Water Works, the Bensley Company purchased part of the Lobos Creek Ranch, including half the water rights to Lobos Creek. The parties agreed to construct a series of flumes, tunnels, and pipes across US Army lands in exchange for fresh water for the Presidio and Fort Point. Transporting water from the creek to the city posed an engineering challenge, as it lay nearly 5 miles (8 km) away. Rebranded as Spring Valley Water Works, the company dammed the mouth of Lobos Creek and built a wooden flume across the dunes at Baker Beach and along the bluffs. Two windmills pumped water from the flume to a storage reservoir that supplied Fort Point’s garrison and the San Francisco National Cemetery. For many years, Lobos Creek was the sole public water source for San Francisco and the Presidio. In 1862, the Spring Valley Company received a permit from the US Army to use Mountain Lake as an additional water source. By 1877, it supplied 2 million gallons (9,092,180 l) per day via a wood and masonry flume 23,500 feet (7,162 m) long. When the windmills failed, mule-drawn wagons hauled water to Fort Point. In 1893, slides along the ocean bluff forced Spring Valley to abandon its flume. The US Army maintained its own flume until 1894, when it built an almost entirely new system of wells at Mountain Lake.

Mountain Lake is located in a 14-acre park designed by William H. Hall around 1875—Hall also designed Golden Gate Park. It is one of the last natural lakes in San Francisco and the only one in the Golden Gate National Recreation Area. Landscape photographer Ansel Adams, who grew up along Lobos Creek, described the riparian habitat: “At times, it was covered with watercress and teeming with minnows, tadpoles, and various larvae. Water bugs skimmed the open surfaces and dragonflies darted above the streambed. In spring, flowers were rampant and fragrant. In heavy fog the creek was eerie, rippling out of nowhere and vanishing into nothingness.” During construction of the Golden Gate Bridge, excess fill compacted the marshlands around the lake, greatly reducing its size. In 1901 the city condemned Lobos Creek’s untreated water as unfit for drinking; however, the U.S. Army maintained that—with a flow of 2 million gallons (9,092,180 l) per day—it was the best available source. Between 1910 and 1912, the federal government built a new pumping plant and water treatment facility at the creek’s mouth. As of 1992, Lobos Creek supplied 60% of the Presidio’s annual water requirements, while two wells at Mountain Lake provided an additional 30%. The US Army imposed conditions on Presidio construction permits, requiring runoff drainage to be directed into Mountain Lake rather than onto Presidio lands. Since then, golf course pesticides and lead emissions from cars burning leaded gasoline have entered the lake. It also became a dumping ground for unwanted pets—crawdads, largemouth bass, goldfish, carp, bullfrogs, turtles and even an alligator, which was discovered and removed in 1996. Read more here and here. Explore more of Lobos Creek and Baker Beach here: