Water Authority Studies Options for Colorado River Water Deliveries


The Water Authority’s Board of Directors is faced with a major decision by the end of 2017 about the future of a long-term deal for water from the Colorado River. The central question is whether to maintain a 45-year Water Transfer Agreement with the Imperial Irrigation District that is scheduled to provide river water for San Diego County through 2047, or to end it 10 years earlier.

Many factors are at play – the cost of transporting San Diego’s water using the Colorado River Aqueduct operated by the Metropolitan Water District of Southern California, the ever-increasing cost of buying other water supplies from MWD, and the future of a strategy that has successfully increased local water supply reliability and reduced regional dependence on MWD by more than half since 1991. 

The Water Authority's independent Colorado River water supplies are delivered through the Colorado River Aqueduct. The Water Authority is assessing potential pipeline and tunnel alignments that could move these supplies from Imperial Dam to San Vicente Reservoir.

Early termination of the Transfer Agreement with IID would result in the loss of 2 million acre-feet of water over the decade dropped from the term. That would require the Water Authority to secure other water sources to maintain its diversified portfolio. 

Other elements are less certain, requiring the Water Authority to analyze numerous variables and forecast a range of potential conditions over several decades to assist the Board’s decision-making process. For instance, the agency is identifying key risk factors affecting water prices, along with environmental and hydrological issues. 

In addition, the Water Authority is assessing potential future water conveyance options that don’t depend on MWD – specifically, the cost and feasibility of building its own aqueduct from the Imperial Valley. That concept has been studied for decades. While a new conveyance facility would be a significant investment, it could deliver significant benefits, such as transporting conserved water from IID through 2077 if the Transfer Agreement is extended for a second term. 

Click here to read a September 2017 Board memo about conveyance options.

A Historic Conservation Agreement

The upcoming decision by the Water Authority Board has its roots in the historic 2003 Colorado River Quantification Settlement Agreement, which helped reduce California’s use of the river to its basic annual apportionment of 4.4 million acre-feet largely through water conservation-and-transfer agreements. 

Since then, increasing volumes of water conserved in the Imperial Valley have been delivered each year to San Diego County under a Transfer Agreement between the Water Authority and the IID. The Water Authority has funded water conservation measures in the Imperial Valley and paid for transporting conserved supplies to San Diego County.  


The Transfer Agreement will provide 100,000 acre-feet of water to San Diego County in 2017, enough to serve 200,000 typical homes. By 2021, the transfer will ramp up to 200,000 acre-feet of water annually – approximately 30 percent of the Water Authority’s annual supplies – and remain at that level for the remainder of the agreement. 

The initial term of the Transfer Agreement is 45 years (2003-2047), with an option for a 30-year extension if both IID and the Water Authority agree to it. The Water Authority also has the unilateral option to end the transfer 10 years early in 2037. That option expires at the end of 2017.

MWD owns the only facility that can deliver the Water Authority’s independent supply of Colorado River water to San Diego County – the 242-mile-long Colorado River Aqueduct. An Exchange Agreement between MWD and the Water Authority governs the deliveries. 

While the initial term of the Transfer Agreement with IID is 45 years, the Exchange Agreement has an initial term of 35 years (2003-2037). The Water Authority has the unilateral option to extend the Exchange Agreement by 10 years so that it aligns with the Transfer Agreement. That option also expires at the end of 2017.