Supply Diversification, Water Efficiency Critical to Region’s Future Water Reliability In Updated Long-Term Water Management Plan

June 23, 2011

The San Diego County Water Authority Board of Directors today adopted its 2010 Urban Water Management Plan (UWMP).  The plan,…

The San Diego County Water Authority Board of Directors today adopted its 2010 Urban Water Management Plan (UWMP).  The plan, a key forecast of regional water demands over the next 25 years and the supply resources needed to meet those demands, calls for the Water Authority and its 24 member agencies to continue to implement and pursue supply diversification projects in response to growing demand and new water supply uncertainties.

“The 2010 Urban Water Management Plan will be a very useful tool for helping us determine how to provide San Diego County with a safe and reliable water supply, and how we may need to adapt in response to supply challenges including regulatory restrictions on imported water deliveries, drought and potential impacts from climate change,” Water Authority Board Chair Michael T. Hogan said.  “What is abundantly clear from this plan is the importance of continuing to use water wisely and continuing to explore and make prudent, cost-effective investments in regional and local water supply projects.”   

The 2010 plan forecasts the region’s growing population will lead to about a 33 percent increase in total regional water demand over the next 20 years.  It estimates demand will rise from approximately 566,400 acre-feet in fiscal year 2010 to about 753,600 acre-feet in 2030 under “normal” supply conditions.  Under extremely dry conditions, regional demand that year may reach about 804,000 acre-feet.  (An acre-foot is about 326,000 gallons, enough to supply two average single-family households of four people for a year.)

While regional water demand is forecast to increase, the 2010 plan’s forecast in 2030 is about 9 percent lower than in the Water Authority’s 2005 UWMP.  The updated plan attributes the lower demand to reduced per capita water consumption in response to rising rates, retail agency compliance with a state mandate to reduce water consumption by 2020 and more focus on multi-family housing in future development, which typically uses less water per person than single-family housing.

To meet that demand, the 2010 plan forecasts implementation of a diverse resource mix that includes a more than 200 percent increase in local supply development, which will reduce the region’s demands for imported water purchases from the Metropolitan Water District of Southern California, the region’s largest imported water supplier.

To achieve this resource mix, the 2010 UWMP expects water deliveries from the Water Authority’s long-term Colorado River water conservation and transfer agreement with the Imperial Irrigation District and from water-conserving canal lining agreements to proceed as planned.  In local supply development, the plan expects the privately developed Carlsbad Seawater Desalination Project to provide 56,000 acre-feet of supply for distribution by the Water Authority to its member agencies by 2016.  The plan also anticipates local water agencies will develop additional local supply projects, such as recycling and brackish groundwater projects, as currently planned.  It also anticipates MWD will develop additional supplies as expected and will provide reliable deliveries from the Bay-Delta and Colorado River to the region.

In addition, the plan states the importance of maintaining water use efficiency to help ensure reliable water supplies for the region in the future.  The 2010 UWMP expects retail agency compliance with state-mandated demand reduction targets will result in approximately 97,000 acre-feet of savings in 2030.

The 2010 plan also recognizes forces beyond the Water Authority’s control – hydrologic drought, litigation, regulation, etc. – that may affect the future availability or desirability of one or more of these supplies.  To address these factors that may affect supply reliability, the 2010 plan includes a new section, Scenario Planning, that looks at the potential supply gaps or other risks if the region cannot implement its diversified set of supply sources as planned. 

The Scenario Planning section also identifies potential strategies that the Water Authority or its member agencies could implement to manage potential supply gaps.  Strategies the Water Authority could implement include potentially developing additional seawater desalination projects.  Such a project at Marine Corps Base Camp Pendleton is in the feasibility study phase.  Other strategies the Water Authority could pursue include executing short-term water transfers and extraordinary water conservation programs. 

Strategies member agencies could implement range from local seawater desalination projects, to expanding groundwater projects, to indirect potable reuse projects.  An indirect potable reuse project uses advanced treatment methods to purify wastewater, inserts that water into reservoirs or groundwater basins for a period of time, and then treats the water again prior to retail consumption.

“Many current factors that may affect future water supplies did not exist or were in the formative stages of being understood when we adopted our last urban water management plan five years ago,” Hogan said.  “Because of this, the 2010 plan explores a broader set of potential future supply scenarios, including imported supply cutbacks during multiple dry years and regulatory-induced shortages.  It also assesses their risks and identifies management strategies for minimizing supply uncertainties.”

The Water Authority coordinated with its member agencies to draft the 2010 UWMP and develop its regional demand forecasts.  The Water Authority also solicited public comment on the draft plan and incorporated public comments into the final plan where appropriate.

All California urban water suppliers are required to prepare an Urban Water Management Plan under the California Urban Water Management Planning Act and update it every five years.  The Water Authority will submit the updated UWMP to the California Department of Water Resources, which uses it to determine the Water Authority’s eligibility for grant funds available through programs administered by the agency.

The 2010 UWMP is available on the Water Authority’s website at

  • The San Diego County Water Authority sustains a $268 billion regional economy and the quality of life for 3.3 million residents through a multi-decade water supply diversification plan, major infrastructure investments and forward-thinking policies that promote fiscal and environmental responsibility. A public agency created in 1944, the Water Authority delivers wholesale water supplies to 23 retail water providers, including cities, special districts and a military base.

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