Drop 2 — End-of-The-Line Reservoir Salvages Colorado River Water

by Joe Gelt

The curiously named Drop 2 reservoir, the latest major Colorado River project to be built to secure a water supply, is to be constructed at the end of the river, one of the last downriver structures in a series of dams, reservoirs and canals that control and distribute Colorado River water.

Among other Colorado River projects Drop 2 stands out as a project of its time, different than other projects built during different periods of Colorado River development. Consider, for example, Hoover Dam, a monumental, multipurpose project built by the federal government in the 1930s. Its purpose was to harness the full flow of the river, considered at the time to be an abundant source of water, in order to control flooding and provide water to arid regions of California and Arizona and hydroelectric energy to millions in adjacent regions.

Over 70 years later, the purpose of Drop 2, which is to be built along the All-American Canal, is to salvage water from a now over allocated river, a project that will be bankrolled, not by the federal government, but by the states of Nevada, Arizona and California as a cooperative venture. The planning and development of the project reflect current political and hydrological realities far different than those that prevailed during previous eras along the river.

State water needs create opportunities

During these dry, drought-stricken times, the seven Colorado River States’ strategies are to protect their river interests and allocations, to be sure they get their share of river water. Arizona especially has reason to fret; in the event of shortages, the state will take the big hit, absorbing the greatest share of the shortages than other Colorado River states. This situation drives the state’s position when negotiating shortage sharing strategies with the other states.

Nevada is nagged by a different Colorado River problem. With a mere 300,000 acre-feet Colorado River allocation a year, compared to Arizona’s 2.8 million acre feet and California’s 4.4, Nevada is decidedly at a disadvantage. The state’s long-term planning goal is to temporarily increase its Colorado River share, its strategy necessarily relying less on a defensive posture than an assertive approach as the state seeks promising opportunities to increase its Colorado River supplies.

Drop 2 is one of those promising opportunities that Nevada vigorously pursued as serving its water interests. The project also serves as a case study of states working together to solve Colorado River issues.
The intent of the Drop 2 reservoir is to salvage Colorado River water supplies that hitherto had been lost.

As it now works, agricultural interests downriver from Lake Mead may request a water delivery. In response, water is released from Lake Mead to downriver farmers or irrigation districts. The released water, however, may take several days to reach its destination. Meanwhile changing conditions such as rain may result in customers cancelling their orders. Unclaimed by U.S. agricultural interests, the released water would then flow to Mexico; it is not counted against Mexico’s legal allocation of 1.5 million acre feet.

The 8,000 acre-foot reservoir, which would be located in California about 25 miles outside Yuma, along the All-American Canal, would provide temporary storage until the water is returned to the system for use. Initially the Southern Nevada Water Authority was to pay the full $172 million cost of the project and correspondingly receive more water. It later became a multistate venture when Nevada approached California and Arizona to share the costs of the project, with each state to contribute about $30 million. Both states agreed.

The reservoir will conserve water for Nevada’s use over the next two decades, with the state expecting to get 400,000 acre feet. Following that period, the additional water will benefit all water users in the lower basin states. The U.S. Bureau of Reclamation figures that operation of the reservoir will readily provide the 600,000 acre feet promised to the three lower basin states by 2036.

Arizona’s Drop 2 payoff

Arizona’s payoff for its investment is 100,000 acre feet of reservoir water, with the Central Arizona Project having access to the water for 20 years, between 2016 and 2036. This would be a propitious time for the state to receive an additional allocation since some projections indicate shortages may be occurring on the Colorado River at that time. If this should occur, Arizona will have additional Drop 2 Colorado River supplies to make up for allocations cut short due to a declared shortage.

Also to Arizona’s benefit is that operation of Drop 2 will slow water declines in Lake Mead. The water level in Lake Mead is the prime deciding factor determining when a Colorado River shortage is declared. If the water level in Lake Mead drops to a level between 1,075 feet to 1,050 feet above sea level, Arizona’s share of water would be reduced by about 320,000 acre-feet. If the level drops between 1,050 feet and 1,025 feet Arizona would lose approximately 400,000 acre-feet, with a more severe drop to 1,025 feet or lower, the state’s reduction is about 480,000 acre-feet.

Whatever maintains Lake Mead levels above the critical trigger points therefore serves Arizona’s water interest.

Nevada’s water needs drives projects

Drop 2 is part of Nevada’s strategy to take fuller advantage of Colorado River water. In a Dec. 20, 2006 ENS story reporting passage of legislation directing the U.S. Bureau of Reclamation to construct the Drop 2 reservoir, Pat Mulroy, general manager of the Southern Nevada Water Authority, is quoted as saying, “Like the Arizona and California water storage banks we have created, this new reservoir allows us to optimize our use of the Colorado River.”

Mulroy is referring to a water banking agreement worked out in 2001 in which the Arizona Water Banking Authority stores sufficient supplies of Colorado River water to enable Nevada to pay for and earn 1.25 million acre feet of long-term storage credits. Nevada could then recover those credits at a later date by paying full price to CAP for delivery, storage and recovery of the stored water that would then go to CAP customers.

This would entitle Nevada, by exchange, to an additional amount of water from Lake Mead. In effect, AWBA would be storing Arizona’s water in Arizona at Nevada’s expense. In turn, Nevada would earn the right to withdraw additional supplies from Lake Mead.

Mulroy said this water banking agreement broke down interstate barriers and promoted common solutions to water supply problems.

Drop 2 is unique

The Drop 2 project is a component within the Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead, an agreement worked out by the seven Colorado River basin states. The agreement in effect formalized a plan to follow if Colorado River supplies should be reduced due to drought.

The agreement and its Drop 2 Project attracted high praise during the December signing ceremony. Interior Secretary Dirk Kempthorne said, “This is the most important agreement among the seven basin states since the original 1922 compact.”

Kempthorne singled out Drop 2 for special notice. He said, “I am particularly impressed by the innovative approaches you have taken to conserve water, especially the construction project known as Drop 2. ... This is truly an innovative example of cooperation among states...that may help other states facing shortages meet their needs.”

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