Lake Merced, located on the outskirts of San Francisco near Ocean Beach and Daly City, is a major fresh 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. It is surrounded by two public golf courses - the nine-hole Fleming course and TPC Harding Park, host of the 2009 President's Cup and 2020 PGA Championship. More than half of the park is managed by the Recreation and Parks Department’s Natural Areas Program, which works to restore and protect habitat for birds and other wildlife, as well as to maintain and improve trails.
To learn more about recreation opportunities at Lake Merced, visit the SF Recreation and Parks website.
Learn more about Lake Merced's Human and Natural History here.
Lake Merced Water Quality
Based on results of the most recent monitoring (December 2022), there is currently a Tier 2 Warning Designation for North, East and South Lake Merced.
Stabilizing Water Levels in Lake Merced
The San Francisco Public Utilities Commission (SFPUC) manages Lake Merced, a beautiful, coastal freshwater lake in the Southwest corner of San Francisco that is an important recreational and environmental asset and resource for the City and the entire Bay Area. The natural areas that surround the lake are home to many plants and animals, including many species of birds and waterfowl. Lake Merced is a destination for all kinds of recreational activities; from boaters, to hikers, bird watchers, bicyclists, picnickers, golfers and people who enjoy a peaceful day of fishing. Lake Merced is also a terminal lake. There are no other significant sources of water into the Lake other than direct rainfall. Declining water levels are a cause for concern regarding the long-term health of Lake Merced for recreational, ecological, and emergency water supply uses.
Stabilizing Lake Merced Levels
Working with our stakeholders and partners, we have implemented a multifaceted approach to address and manage decades of decreasing lake levels.
Daly City Coordination
These efforts include development of recycled water to replace groundwater pumping for irrigation around the lake and advanced planning in coordination with the City of Daly City to implement the Vista Grande Project to divert treated and untreated stormwater to the lake during rain events. Learn more.
Westside Enhanced Recycled Water
We are currently evaluating the potential to further increase and stabilize lake levels by utilizing available/excess supply from the soon to be completed Westside Enhanced Water Recycling Plant located at the Oceanside Wastewater Treatment Plant. The enhanced treatment process will produce water to safely irrigate Golden Gate Park, the San Francisco Zoo, the Lincoln Park Golf Course and other parks and open space areas of the City. This would potentially provide a year-round source of highly treated water for the lake not dependent on rainfall and allow us flexibility to maintain higher lake levels that support recreational uses and the habitat of this amazing watershed. Learn more.
Water Levels and Quality Monitoring
Lake Merced is considered a shallow eutrophic lake; meaning that it is rich in minerals and organic nutrients that promote proliferation of plant life including algae, which can lead to depressed dissolved oxygen levels. The lake is on the California 303 (d) list for pH and dissolved oxygen.
The SFPUC has conducted quarterly water sampling at Lake Merced since 1997 to monitor the condition of the lake. Starting in 2020 SFPUC also includes monitoring for harmful algal blooms as well.
View the sampling results and analysis here:
Lake Merced Levels
As part of the Watershed Management activities the SFPUC measures and records surface water levels at Lake Merced using an automated pressure transducer. Lake Merced water levels are recorded at least daily and are presented below.
See the lake levels Hydrograph. The gap in data was the result of construction activities during the Seismic Upgrades and Retrofit of the Lake Merced Pump Station.
About Harmful Algal Blooms and Lake Merced
What is a Harmful Algal Bloom?
Algae are organisms that live in various water bodies. Under certain conditions algae and blue green algae (cyanobacteria) can grow very quickly in a short period of time and can cause harm to people, animals, or the local ecology. Harmful Algal Blooms (HAB’s) have become an increasing issue in urban lakes and reservoirs across California including Lake Merced.
What does it look like?
Harmful algal blooms can look like foam, scum, algal mats, paint on the surface of water, or water that is green and has very low transparency. The harmful algae are generally concentrated at the surface but can exist at all depths of the water body. These blooms can produce toxins which at certain concentrations can be harmful to humans and animals, as well as produce unpleasant odors, caught fish not suitable for human consumption, and contribute to poor water quality.
What is the SFPUC doing?
The SFPUC is coordinating with San Francisco Recreation and Park Department as well as the local Regional Water Quality Control Board (RWQCB), to keep the public notified of conditions in Lake Merced. The SFPUC monitors general water quality in the lake quarterly and monitors levels of cyanobacteria and potentially toxic algal by-products monthly. Results are reported to the RWQCB quarterly. San Francisco Recreation and Parks Department posts signage visible to the public in strategic locations around the lake to inform people of the potential threat level of water contact based on these monitoring results.
Additional information can be found at: https://mywaterquality.ca.gov/habs/
Past and Future of 520 John Muir Drive (Former Pacific Rod and Gun Club Site)
The property at 520 John Muir Drive adjacent to Lake Merced is owned by the San Francisco Public Utilities Commission and following redevelopment will be operated by the San Francisco Recreation and Parks Department.
The property had been operated as skeet and trap shooting facility by the Pacific Rod and Gun Club from 1934 to 2015. These activities resulted in lead shotgun pellets and other debris falling onto the site and into the lake. The Pacific Rod and Gun Club vacated the site in 2015.
The SFPUC removed the contaminants from the site and restored the soil in order to protect both the health of the public and the Lake environment under the oversight of the San Francisco Bay Regional Water Quality Control Board. The site clean up was completed in 2016. The property is currently closed to the public.
What is next for 520 John Muir Drive - Lake Merced West Redevelopment
The San Francisco Recreation and Parks Department proposes the future uses for the property as part of the Lake Merced West Redevelopment Project. The proposed project consists of the construction and operation of the Lake Merced West recreation facility. The recreation facility would offer an array of active and passive activities open to the public, such as trail use, picnicking, paddle boarding, kayaking, fishing, fitness activities, a ropes course, bird watching, space for outdoor exercise, skateboarding, multi-use courts for basketball and other activities, restaurant dining, and indoor space for gatherings such as community meetings and birthday parties. The facility would include areas that could be used flexibly for a wide variety of uses such as picnics, larger gatherings, or pop-up markets; as well as areas designated for programmed activities. The SFPUC’s new Arborist Facility would be located in the southeastern portion of the site.
The project is currently under environmental review by the San Francisco Planning Department as the lead agency. The draft Environmental Impact Report (EIR) will be published on February 23, 2022. The public review period will extend to April 11, 2022, with final EIR certification anticipated in early 2023.
The Draft EIR and ways to comment will be located at the SF Planning’s website here: https://sfplanning.org/sfceqadocs and search for Lake Merced West.