Lake Merced is located in the southwest corner of San Francisco near Skyline and Lake Merced Boulevards.  It consists of four inter-connected freshwater lakes North Lake, South Lake, East Lake and Impound Lake that are fed by rain water and seepage from historic springs and creeks.  The Lake is a major natural habitat for many species of birds and waterfowl and a regional recreational venue offering fishing, boating, bicycling and wildlife viewing.

Recreation
Lake Merced offers a variety of recreational opportunities to visitors: 

• Trails for walking, jogging, dog-walking, biking and bird watching
• Fishing pier and boat launch
• Harding Park /Jack Fleming Municipal Golf Course, a world-class 18 hole and executive 9 hole golf course  

Water Use & Management
Lake Merced is an emergency source of water for the City of San Francisco to be used for fire fighting or sanitation purposes if no other sources of water are available.  The San Francisco Recreation and Park Department manages the recreational areas of the Lake under a 1950 agreement with the San Francisco Public Utilities Commission. The SFPUC manages the water aspects of the Lake.

The Westside Basin
Rock, sand, gravel, or soil that can hold and yield usable amounts of groundwater is called an aquifer.  The Westside Basin is a productive aquifer that underlies the land just north of Golden Gate Park to the San Francisco International Airport at its southern boundary.  Groundwater in the basin is replenished primarily by rainfall and irrigation. 

Lake Water Levels
Historically Lake Merced has been replenished by storm water runoff from the surrounding watershed. As the areas surrounding the lake became developed, less rainfall was reaching the Lake and recharging the underlying aquifer.  The Cities of Daly City, San Francisco and San Bruno, as well as several golf courses, cemeteries, and some private users, rely on groundwater extracted from the Westside Basin for drinking water and irrigation.  As more groundwater is pumped from deeper aquifers to meet growing water needs and increasing urbanization, water in the shallow aquifer that is a part of Lake Merced now flows slowly towards pumping depressions in Northern San Mateo County.  The problem is exacerbated by reduction of stormwater flows to the shallow aquifer, which are now for the most part routed to the Ocean or to San Francisco's Oceanside Wastewater Treatment Plant.

Landmark Agreement
The City of Daly City’s Northern San Mateo County Sanitation District, San Francisco Public Utilities Commission and three private golf courses (Olympic Club, Lake Merced Golf Club and San Francisco Golf Club) have reached a landmark 50-year agreement to replenish groundwater in the Westside Basin by providing alternative water supplies for drinking and irrigation.  The agreement will address long-standing problems that have depleted Westside Basin groundwater levels, including Lake Merced, and diminished its water quality over time.

This multi-faceted program will work to raise Westside Basin groundwater levels.  The City of Daly City plans to build a new $7 million tertiary recycled water treatment plant at Lake Merced and John Daly Boulevards.  Three area golf courses -- Olympic Club, Lake Merced Golf Club, and the San Francisco Golf Club -- have agreed to use the recycled water from the facility for irrigation instead of pumping groundwater.   The groundwater saved will help restore declining water levels at Lake Merced and preserve water supplies in the underlying aquifer. 

In a pilot conjunctive use program, the City of Daly City agreed to limit its groundwater pumping (a major source of Daly City’s water) in exchange for available surplus SFPUC drinking water supplies in wet years, to replenish aquifer water levels.   
 

VISTA GRANDE
The Vista Grande Watershed includes approximately 2.5 square miles in Daly City and San Mateo County and the Vista Grande Canal and tunnel in San Francisco.  The northern border of the watershed is in San Francisco, adjacent to Lake Merced and includes the Vista Grande Canal and Tunnel near John Muir Drive.  The Western border of the watershed is the Pacific Ocean.  A large drainage area that includes much of Daly City and a portion of unincorporated San Mateo County characterizes the watershed. Storm flows from Daly City drain into the Vista Grande Watershed, entering the Vista Grande Canal and Tunnel before being discharged through an outfall on Ocean Beach near Fort Funston.