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As an Excellent Winter Transitions to an Uncertain Spring, How Secure are Arizona’s Water Supplies?

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Arizona’s water supplies have been front page news for months.  Both local and national media have reported on increasingly serious shortages on the Colorado River and the inability of the states that rely on the River to reach consensus on how to share those shortages.  Other outlets have reported on issues relating to Arizona’s groundwater resources, including creation of a new irrigation non-expansion area (INA) in the Hualapai Groundwater Basin north of Kingman, and the first-ever voter-approved active management area (AMA) in the Douglas Groundwater Basin in southeastern Arizona.  The Hualapai INA and Douglas AMA are tangible indications of growing concerns about unregulated groundwater withdrawals in rural areas of Arizona.

While this widespread media coverage has painted a grim picture of Arizona’s current water situation, at the same time, the media have also widely reported on an extraordinarily wet and snowy winter in Arizona and throughout the southwestern United States.  Conditions in three watersheds that directly affect Arizona’s water supply – the Salt-Verde, Gila, and Colorado River watersheds – are excellent because numerous winter storms brought abundant snow to the high country and rain to lower elevations.  For example, snowpack in the Salt and Verde River watershed was so deep that by early March, the Salt River Project began controlled releases of water from its reservoir system to ensure there would be enough capacity to hold expected runoff as the snow melted.  Those releases have continued through late April, and the SRP reservoir system is currently 99% full, as compared to 71% at this time last year.

Conditions in the Colorado River watershed are not nearly so good, but higher elevations in the watershed have had a very good winter, with basin-wide snowpack exceeding 160% of the 30-year average in early April.  As a result, the United States Bureau of Reclamation last week predicted that the most probable inflow into Lake Powell from April through July this year will be 11.3 million acre-feet, 177% of the 30-year average.  While this is undeniably good news, the effects of more than 20 years of intense drought in the Colorado River watershed had so depleted Lake Powell and Lake Mead – the largest and most critical reservoirs in the watershed – that only modest improvements in the system are expected this year.  This reality prompted the Department of the Interior to issue earlier this month its draft Supplemental Environmental Impact Statement proposing major cuts in water deliveries to the lower Basin states of Arizona, California, and Nevada over the next three years (see Biden Administration Considers Interrupting the “Law of the River” Status Quo by Snell & Wilmer attorney Fred Breedlove).  So, what does this all mean for Arizona’s water supply?  The good news is that Arizona has a very diverse water portfolio to draw on, including Colorado River water, in-state surface water, groundwater, recycled water (treated wastewater effluent), and large quantities of water that have been stored in underground aquifers to be available when extended droughts cause shortages in Arizona’s other supplies.  Over the next several weeks, we will delve into the details of this portfolio to demonstrate Arizona’s robust ability to contend with current and future water challenges.