In 2009, California’s legislature passed the Water Conservation Act, which calls for a 20 percent reduction in water use in the state by 2020. But some cities are aiming much higher. Three years ago, the city of Santa Monica, Calif., reported that it imported 84 percent of its water. By 2020, however, the city will eliminate its reliance on imported water under normal conditions from the Sacramento-San Joaquin River Delta and the Colorado River by 2020. Will other cities follow its lead?

A number of California municipalities already are. On a larger scale, Santa Monica’s ambitious plans combined with efforts and targets from four other Southern California water agencies, should shrink the area’s use of imported water by 40 billion gallons annually by 2035, according to a recent analysis by the Natural Resources Defense Council (NRDC). This is more than the total annual water use for the city of Sacramento.

The report, “Tackling Water Scarcity: Five Southern California Water Agencies Lead the Way to a More Sustainable Tomorrow,” examined the 2010 water management plans from more than 350 water agencies in California. Under the state’s Urban Water Management Planning Act, urban water suppliers that provide over 3,000 acre-feet of water annually or serve more than 3,000 connections are required to formally evaluate their water sources over a 20-year planning period considering normal, dry, and multiple dry years. The resulting Urban Water Management Plans are submitted to the state’s Department of Water Resources and must be updated every five years. The 2010 plans, the most recent completed, were the first to reflect the 20 percent by 2020 reduction goal (dubbed by former Governor Arnold Schwarzenegger as the 20×2020 Plan).

The city of Santa Monica, the city of Camarillo, Ventura County Water District No. 1, the Long Beach Water Department, and the Los Angeles Department of Water and Power were identified as the top five agencies in terms of targeted reductions. Together, their plans should reduce their reliance on imported Bay Delta or Colorado River water by a minimum of 35 percent (and up to Santa Monica’s goal of 100 percent) by 2035, through techniques such as stormwater harvesting; better groundwater management; and water conservation, recycling, and efficiency efforts.

Improving local water sources has been a key focus for the five agencies. In 2011, Santa Monica completed a groundwater remediation effort that opened five local wells that should increase the amount of locally produced water to 70 percent. Camarillo, meanwhile, is constructing a regional groundwater desalter that should increase local groundwater allocation by 5,000 acre-feet per year when it is completed in 2016 or 2017, and Ventura County is also building a new desalter that will use reverse-osmosis treatment technology to produce potable-quality water from groundwater. The Ventura Country plant also will produce recycled water and plans are in place to double its treatment capacity and expand its distribution system to serve more customers. Focusing on efficiency, the Long Beach Water Department is implementing a landscape conversion program offering the highest landscape conversion incentive in the state–$3 per square foot—for landowners to replace grass lawns with more water-efficient options. The department is also planning to increase the distribution of recycled water produced at the Long Beach Water Reclamation Plant, which turns wastewater into recycled water that is suitable for irrigation uses.

These locally focused techniques create what NRDC calls the “virtual river,” says Kate Poole, co-author of the analysis and senior attorney and head of NRDC’s water and wildlife project, and “are the wave of the future in terms of how we are going to stabilize and expand our water supply.” Recognizing that water scarcity is now an issue in California, Poole hopes that the case studies in the report can serve as inspiration for other geographic regions and utilities. “[Water scarcity] is a reality out here in California already, but I think it is becoming more of a reality across the United States as climate change really starts affecting hydrology. Other states are starting to grapple with these issues as well. What we tried to do here is highlight some of what we think are innovative water agencies because they’re showing you how it can be done. Here are some good plans on how to take advantage of the local attributes you have available and expand your water supply while reducing your dependence on uncertain sources. Certainly the Colorado River and the California Bay Delta are increasingly uncertain sources for water supply in California.”

Part of Santa Monica’s large imported water reduction is due to a groundwater remediation effort that opened five wells that helped reduce imported water use from 84 percent down to 30 percent of the city’s total water supply. The effort also saved the city significant money, dropped the cost per acre-foot from $794 for the purchase of treated imported water to $330 for local production. The city’s goal is to have 72 percent of its water come from local groundwater by 2020, with the remaining 28 percent coming from graywater, rainwater, stormwater, and recycled water, according to the NRDC analysis. The city’s Office of Sustainability and the Environment reports that by 2011, Santa Monica’s use of local water rose to 51 percent of total water supply, marking progress toward the 2020 goal.

Click here to download the NRDC analysis brief and click here for the 2010 City of Santa Monica Urban Water Management Plan. As assessment of state water efficiency and conservation programs from the Alliance for Water Efficiency and the Environmental Law Institute can be accessed here.