Arizona Water Bank

The Water Authority approved an agreement in December 2004 with Arizona that allows Nevada to store water in Arizona's groundwater aquifer.

Under the agreement, Nevada will pay Arizona to store unused Colorado River water for future use.

An amendment to a 2001 groundwater banking agreement, this pact solidifies the quantity of water to be stored, guaranteeing Nevada access to the entire 1.25 million acre-feet (more than 400 billion gallons of water). Under the terms of the agreement, SNWA could begin withdrawing 20,000 acre-feet of credits per year in 2007, ramping up to as much as 40,000 acre-feet annually by 2011.

Because the withdrawals will be taken from Lake Mead, Nevada also will receive return-flow credits for the portion used indoors, further extending the value of this pact.

"This represents a landmark in cooperation between the states that rely upon the Colorado River," said SNWA General Manager Pat Mulroy. "For nearly a century, the basin states have focused primarily on protecting their share of the river. These kind of partnerships will allow the entire Colorado River basin to weather the drought."

Under the terms of the agreement, SNWA will pay Arizona $100 million in 2005, then make 10 annual installments of $23 million beginning in 2009.

"As we move forward with our long-term water planning, this agreement guarantees us an additional water supply potentially for the next five decades," Mulroy said. "It does not eliminate the need for us to continue our conservation efforts or develop water supplies that are independent of the Colorado River. However, this agreement does provide the bridge we need to help insulate the residents of Southern Nevada from ongoing drought."

Earlier this year, the SNWA announced plans to exercise its water rights along the Virgin and Muddy rivers and act upon groundwater applications it holds in basins within Clark, Lincoln and White Pine counties. Because these projects will require both extensive environmental analyses and significant construction, the majority of these in-state supplies will not be available to Southern Nevada for nearly another decade.

How the banking works
As part of the water banking agreement, Arizona stores available Colorado River water in an underground aquifer. Nevada receives "credits" for the water stored in this groundwater "bank."

When Nevada needs to recover some of this banked water, it uses its storage credits and withdraws a portion of Arizona's Colorado River water directly from Lake Mead. Arizona then withdraws the same amount of water from its groundwater aquifer.