Water Supply Scarcity in Southern California: Assessing Water District Level Strategies
Urban water scarcity is an ongoing reality in California, especially, in Southern
California with its arid climate and cyclical droughts. Southern California relies on upstate water
imports provided by the Metropolitan Water District of Southern California (MWD) for a
significant portion of its water supply. MWD also imports water from the Colorado River,
conveyed through the Colorado River Aqueduct. Key to the transportation of water from the
mountains in Northern California to the south is the Sacramento-San Joaquin River Delta,
vulnerable to aging levees, subsidence and saltwater intrusion. In addition, the environmental
deterioration of the Sacramento-San Joaquin River Delta, habitat to several endangered species,
has led to ongoing restrictions on MWD water deliveries to Southern California water agencies.
This has renewed efforts to both provide for the environmental improvement of the Delta
ecosystem, as well as to find a solution for water conveyance, either through a canal, or more
recently, through twin tunnels. In addition, the susceptibility of the Sacramento-San Joaquin
River Delta to a major Bay Area earthquake increases the threat of disruption of water imports
for Southern California.
Climate Change Amplifies Reliability Challenges. The reliability of water supply for Southern
California is thus already precarious. Climate change impacts will further aggravate water
scarcity throughout the State. According to the State’s Climate Adaptation Strategy (2009),
snowpack in the Sierra Nevada mountains, a major state source of water storage, is already
decreasing and climate change models indicate that precipitation in the mountains will be
increasingly in the form of rain, not snow. The State relies on the runoff from the snowpack in
the Sierra Nevada to provide water during the warmer months from late spring to early autumn,
especially for the southern part of the State. The Climate Adaptation Strategy estimates that the
snowpack may be reduced from its mid-20th century average by 25-40% by 2050. Climate
change impacts for the State also include a 12-35 % overall decrease in precipitation by midcentury.
California’s Water Conservation Efforts. To deal with water scarcity, the State initiated in the
early 1990s a voluntary urban water conservation program managed by the California Urban
Water Conservation Council (CUWCC), which promoted the implementation of Best
Management Practices (BMPs) to achieve more efficient water use. In response to the
Governor’s call for an aggressive urban water conservation plan, in 2009 state agencies with water policy responsibility developed a plan with a target of reducing urban water use through
conservation measures by 20% by 2020. This target was incorporated into the 2009
Comprehensive Water Package that was passed by the California legislature in November of
2009. The Water Package (CA Dept. of Water Resources 2009a) included an $11B bond issue
that was to be voted upon in the November 2010 ballot, allocating several billion to fix the Delta,
and funding for conservation and other water initiatives, including the development of Integrated
Water Management Plans. As part of the 2009 state legislation, regional and local water districts
were required and provided incentives to enact conservation and other measures to develop
“diverse regional water supply portfolios that will increase water supply reliability and reduce
dependence on the Delta” (S.B. X7-7, Sect. 1, Part 2.55, Chapt. 10608 (c)). Urban water
agencies are required to report their baselines and targets to meet 20 x 2020 goals in their Urban
Water Management Plans (UWMPs), which are updated every five years.
Assessing the Effectiveness of Conservation Strategies.
Analyzing the Cost-Effectiveness of Strategies.
Identifying Robust Strategies for the Future.