Urban water scarcity is an ongoing reality in arid Southern California, and the region remains dependent on imported water, according to a new two-year analysis of water conservation management in Southern California.

Led by researchers at USC, the report, “Water Supply Scarcity in Southern California,” examined water management strategies that were implemented in 2009 as part of legislation to encourage conservation and reduce dependence on single sources of water.

The report provided a critical assessment of continued water supply vulnerabilities and examined whether the region is on track to meet conservation goals, as well as the most cost-efficient strategies for water conservation in the future.

“We still have significant challenges to overcome in water management with political fragmentation and skepticism,” said Hilda Blanco, lead investigator on the report and research professor at the USC Price School of Public Policy. “By midcentury, high-warming estimates could lead to chaos for local water providers and even under average warming scenarios [may lead to] water agencies [having] to make deep adjustments in their plans or face less water for everyone.”

Published by the USC Center for Sustainable Cities, the report showed that Southern California needs imported water to quench its thirst.

The water districts analyzed in the report — the Los Angeles Department of Water and Power (LADWP), the Cucamonga Valley Water District and the Huntington Beach Utilities Department — all still lean on imported water from the Sacramento-San Joaquin River Delta and the Colorado River as a main water source.

For the LADWP, 52 percent of water is imported, 36 percent comes from the Los Angeles Aqueduct, 11 percent comes from groundwater and less than 1 percent is recycled, the report found. The largest available current source of groundwater for the LADWP is the San Fernando Basin, which is heavily polluted and a designated U.S. Environmental Protection Agency Superfund cleanup site.

In contrast, Huntington Beach, which used the least imported water of the Southern California regions studied, imports 32 percent of its water and gets 68 percent from local groundwater.

However, the researchers found that the LADWP has the most coherent plan in place to address water shortages in the future, including cleanup of the San Fernando Basin, tiered pricing for water use and municipal programs to encourage the adoption of water-saving appliances, such as rebates or mandates for new construction. The LADWP also plans to spend more then $500 million over the next decade to expand the infrastructure for recycled water and to decrease the proportion of imported water to 24 percent.

“By setting low targets, many agencies have ensured that they will have little trouble meeting water conservation goals,” said Blanco, who noted that Southern California agencies were allowed to set their own baselines for the state’s goal of 20 percent reduction in per capita water use by 2020. “The management of groundwater is so fragmented among multiple basins and water rights holders that the region lacks the ability to plan realistically for the future. The state needs a comprehensive strategy to manage this critical resource.”

Among the study’s other key findings:

For the LADWP, imported water is the most expensive water resource in terms of energy used and greenhouse gases emitted. Imported water from Northern California and elsewhere is 12 to 15 times more energy intensive than water from the LA Aqueduct (which is conveyed by gravity), and causes eight to 10 times the emission of greenhouse gases.

Seventy percent of the LADWP demand for water comes from residential customers: 38 percent from single-family homes and 32 percent from multifamily residences. Multifamily developments tend to use less water per capita than single-family homes.

In the Cucamonga Valley Water District, 22 percent of water demand is for landscaping. More than half of water demand (about 55 percent of total water usage) is for single-family homes.

In Huntington Beach, declining population has been mirrored by decline in water demand. Since 1999, per capita water use has constantly declined.

Water conservation strategies vary in cost-effectiveness, and what works in one district might be a wash in another. For example, the report showed the replacement of turf with synthetic turf is borderline cost-effective in the Cucamonga Valley Water District, with a benefit-cost ratio of 0.96. In contrast, outdoor weather-based irrigation controllers have a benefit-cost ratio of over 11, meaning the region gets back $11 in savings for every dollar spent.

The report made several recommendations, including investment in technological innovations for water irrigation, continuing research on climate change impacts on water resources and a statewide coordinated strategy for water management.

The Haynes Foundation funded the research. Lowell Stott of USC, Marina Alberti of the University of Washington and Joshua Newell of the University of Michigan contributed to the report.

More stories about: Research