The Dominguez Channel Watershed covers approximately 70,000 acres and is located in the southern portion of the Los Angeles Basin. Approximately 43,400 acres of the watershed drains to the 15.7-mile-long Dominguez Channel which begins in Hawthorne and discharges into the Los Angeles Harbor in the east basin. The remaining approximately 26,600 acres, which includes Wilmington Drain and Machado Lake, drains directly to the Los Angeles Harbor independently of Dominguez Channel.
Parts of Los Angeles County and over 15 cities and other jurisdictions are located in the Dominguez Channel Watershed. The City of Los Angeles comprises 21% of the watershed’s area. It is bounded by Manchester Boulevard to the north and the Los Angeles and Long Beach Harbors to the south. The western areas include portions of El Segundo, Manhattan Beach, Redondo Beach, Torrance and the Palos Verdes Hills. Portions of Willowbrook, West Compton and Carson are located in the eastern portion of the watershed.
Over 90% percent of the land area is developed. Residential use covers about 41% and another 44% is industrial, commercial, and transportation related. Overall, the watershed is approximately 61% impervious. Constructed waterways are predominant, however some small, natural creeks are located in the hills of the Palos Verdes Peninsula.
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.The Dominguez Channel and other selected water bodies in its watershed, including the Los Angeles Harbor are impaired by pollutants (i.e., trash, metals, bacteria, nutrients) mainly because of the watershed’s large, dense population and the amount of impervious ground surface that prevents large quantities of runoff from infiltrating into the soils. Currently there are several TMDLs for waterbodies in the Watershed, including:
The City along with other agencies in the Dominguez Channel watershed is currently developing an Enhanced Watershed Management Program (EWMP). The EWMP will identify the measures for compliance with all Dominguez Channel 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.