The Santa Monica Bay Watershed, with its 55 miles of coastline and beaches, covers 385 square miles (182,000 acres). Its northern boundary extends along the crest of the Santa Monica Mountains from the Ventura-Los Angeles County line on the west to the Ballona Creek Watershed on the east. South of Ballona Creek the natural drainage area is a narrow strip that extends south from Ballona Creek to the tip of the Palos Verdes Peninsula, bordered by the Pacific Ocean to the west and the Dominguez Channel Watershed to the east. The entire watershed has approximately 200 separate storm drain outlets that convey over 30 billion gallons of runoff to the Bay each year.
The Santa Monica Bay Watershed contains 27 subwatersheds that are separated into seven jurisdictions. Much of the terrain in the watershed’s northern portion is rugged open space and contains many canyons that carry runoff directly to the Bay. Topanga and Malibu Creeks are the two largest watercourses in this area. The creeks are fed both by tributary creeks and by channelized storm drains in and near developed areas. Portions of Malibu, Agoura Hills, Westlake Village, and Los Angeles are located in this part of the Watershed. The mid- and southern portions of the Watershed are more urban and contain portions of Los Angeles, Santa Monica, El Segundo, Manhattan Beach, Redondo Beach, Palos Verdes Estates and Rancho Palos Verdes. This area is highly developed with a network of storm drains carrying flows to the Bay.
Overall, 27,500 acres of the Santa Monica Bay Watershed are within the City of Los Angeles. The City has land in Jurisdictions 1, 2, 3 and 7 but the primary portion is located in Jurisdictions 2 and 3. This summary will focus on the activities in these jurisdictions which are pimarily led by the cities of Los Angeles and Santa Monica. Jurisdictions 2 and 3 are highly urbanized and the land use within these jurisdictions (including the undeveloped canyons) is 32% residential, 48% open space/parks/canyons, and 20% commercial/industrial/transportation/educational.
As of March 2012, the US EPA has approved 22 TMDLs throughout the region that list the City of Los Angeles as a responsible jurisdiction. These include waterbodies within the Los Angeles River, Ballona Creek, Santa Monica Bay and Dominguez Channel Watersheds.Santa Monica Bay’s beaches and other waterbodies within the watershed are impaired by pollutants (i.e., debris, bacteria and toxics) mainly because portions of the watershed have large, dense populations and significant amounts of impervious ground surface that prevents large quantities of runoff from infiltrating into the soils. Currently there are several TMDLs for waterbodies in the City’s portion of the Watershed, including:
The City along with other agencies in the Santa Monica Bay watershed is currently developing an Enhanced Watershed Management Program (EWMP). The EWMP will identify the measures for compliance with all Santa Monica Bay TMDLs and other water quality mandates while maximizing potential benefits of stormwater for local water supply. The draft EWMP will be finalized by April 2016 after review by the Regional Water Quality Control Board.
A Total Maximum Daily Load (TMDL) is the maximum amount of a specific pollutant, such as trash, bacteria, or pesticides that could be discharged into a waterbody without causing it to become impaired. Development of TMDLs, which are driven by the Clean Water Act, are an important step in cleaning up our creeks, lakes, rivers, and beaches.