Metropolitan Water District ‘Water Supplies Report’ found inadequate

May 22, 2003

The San Diego County Water Authority board of directors, responding to a presentation on the Metropolitan Water District of Southern…

The San Diego County Water Authority board of directors, responding to a presentation on the Metropolitan Water District of Southern California’s “Report on Metropolitan’s Water Supplies,” voiced concerns over the report’s accuracy and the validity of its projected supplies. MWD’s report provides information regarding its projected water demands and the supplies that are available to meet those demands in the future.

MWD lost more than half its Colorado River Aqueduct supply this year, due to the failure to execute the Quantification Settlement Agreement. Consequently, a great deal of attention is being paid to MWD’s water supply reliability. The 670,000 acre-feet of Colorado River water that MWD lost is equal to about 30 percent of its current demand of 2.4 million-acre-feet. To make up for the lost supplies, MWD plans an unprecedented, one-year draw down of its water storage and dry-year option supplies.

“The Water Authority’s analysis of MWD’s water supply report reveals that its near- and long-term supply reliability has been severely compromised by the large loss of core supply resulting from the failure to so-far complete the Quantification Settlement Agreement,” said Bernie Rhinerson, chairman of the Water Authority’s board of directors.

Several conclusions were drawn from the Water Authority’s analysis of the MWD report. The overriding consideration for MWD water supply reliability is how MWD will deal with the loss of the 670,000 acre-feet of core Colorado River supply and the loss of long-term water supply programs that make up the Quantification Settlement Agreement. This is especially important over the next 10 to 15 years because additional local supplies take time to develop and alternative imported supplies (transfers from Northern California) are expensive and difficult to transport.

In general terms, MWD’s report states the agency can withstand the loss of Colorado River supply and meet all member agency demands over the next 15 to 20 years. MWD attributes this ability to its investments in surface storage, groundwater and conjunctive use. According to the report, MWD will manage the loss of Colorado River supplies by using storage, “enhanced” conservation, and additional local supply development. However, the Water Authority’s analysis faults the MWD report for assuming the QSA supplies will be available in both “Current Supplies” and “Supplies Under Development,” and then stating that the lack of the QSA does not pose an imminent threat to MWD reliability. The report does not clearly state that the QSA must be executed for the QSA supplies to become available.

“Metropolitan’s report hides both the benefits of the QSA and the consequences of not executing the QSA,” Rhinerson said.

MWD has large volumes of water stored in its surface reservoirs and groundwater basins, but this storage is at risk of being halved by a single dry year. The report indicates that MWD will need to withdraw about half of its surface storage, predominantly from Diamond Valley Lake reservoir, if a single dry year occurs. If this happens, it will not be possible for MWD to refill the Diamond Valley Lake reservoir without a series of wet years on the State Water Project in Northern California, the Water Authority’s analysis concluded.

Consecutive dry years could have the same devastating water shortage effects as occurred during 1987-92, a period of six consecutive years that were either dry or critically dry on the State Water Project. Unless the QSA is executed, MWD cannot hope to have a full Colorado River Aqueduct to rely upon, as it did in the 1987-92 drought.

The Authority’s review of MWD’s 2003 report produced the following conclusions:

  1. The report overstates current supplies by including projects that have not been implemented, are not complete, or require execution of the QSA to be implemented. Some projects, such as Semitropic, Arvin Edison, and North Las Posas, show supply yields above current capacity and significantly higher than MWD has reported in numerous other reports.


  2. The report assumes execution of the QSA by including QSA supplies in both current and future supplies while concluding that reduced Colorado River supplies will be managed through use of storage, “enhanced” conservation, and additional local supplies (groundwater, recycling, seawater desalination).


  3. The report is silent on MWD’s water supply risks if the QSA is not executed.The report assumes that MWD will obtain an average of about 75 percent of its SWP entitlement in future years, based upon DWR studies. However, from 1992-2001 the SWP was only able to deliver an average of 54 percent of contractor entitlement with large swings in supply availability from year to year. Over the entire history of the State Water Project, it has averaged only 63 percent of full deliveries annually.


  4. If the QSA is not executed and consecutive dry years occur on the State Water Project, MWD’s plan for withdrawing Diamond Valley Lake storage during dry years seriously increases risks of water shortages. The report revises prudent withdrawal rates of 150,000 acre-feet-per-year to allow more than 400,000 acre-feet to be withdrawn in a single year. MWD no longer has a full Colorado River Aqueduct as a backstop to replenish such withdrawals, as it did in the 1987-92 drought.


  5. MWD’s report includes a “Disclosure Statement” that raises serious questions about the report’s utility for member agency compliance with SB 221 (Kuehl) and SB 610 (Costa). The statement notes that MWD and other wholesalers “do not have verification responsibilities” under the legislation, and asserts “Although all information in this report is believed to be accurate as of the time of issuance, Metropolitan does not warrant as to the reliability of information contained in this report supplied by third parties. Readers should make their own judgments to the extent on which they rely on the information in this report.”

“MWD’s board will be requested to approve the QSA later this year,” Rhinerson said. “The Water Authority is concerned that the water supply and economic risks of failing to execute the QSA need to be well understood. These risks are not restricted to Southern California, but extend throughout the state because of the impact that reduced Colorado River supplies has on the SWP and other northern California supply options.”

The San Diego County Water Authority is a public agency serving the San Diego region as a wholesale supplier of water from the Colorado River and Northern California. The Water Authority works through its 23 member agencies to provide a safe, reliable water supply to support our region’s $126 billion economy and the quality of life of nearly 3 million residents.

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  • 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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