Putting Water Year 2023 in Context: Caution, Conservation Still Best for the West

September marked the end of Water Year 2023, and it was certainly one for the books. Snowpack, runoff and increases in reservoir storage all were all unusually large. Current estimates for the year’s total runoff in the Colorado River Basin and increases in reservoir storage were the second largest recorded for the 21st century.

Managers, irrigators and community leaders responsible for water supply in our arid region are likely breathing a sigh of relief for the welcome pause to the ongoing drought that Western states have endured since the beginning of the 21st century.

But historical data shows that we aren’t out of the woods yet, according to a new commentary written by Jack Schmidt, director of the Center for Colorado River Studies and emeritus professor from the Quinney College of Natural Resources.

In order to refill reservoirs to 1999 levels (the last time the reservoirs were completely full), the region would need an additional three to six years of unusually high precipitation, based on historical data. Such a string of exceptionally wet years hasn’t happened since the mid-1980s, the data shows, and likely won’t occur anytime soon.

A Water Year is the 12-month period used by hydrologists and water managers to measure annual precipitation. It extends from Oct. 1 to Sept. 30 of the following calendar year, spanning the entirety of winter and spring runoff.

There have been notably wet years in our recent past; 2011, 2017 and 2019 each provided surplus runoff water that buoyed levels in the main reservoirs of the Colorado River Basin (Mead and Powell). But that extra storage never lasted long — the excess was consumed within two years, on average, despite a number of administrative agreements with the goal of decreasing water consumption, Schmidt said.

We are on a similar track this year, despite the record water year.

Water storage is measured in millions of acre feet (maf). Since mid-July when the snowmelt season ended, reservoir storage has again started to decline. The Colorado River basin’s reservoirs lost 1.3 maf of water storage between mid-July and the end of September, of which 0.3 maf was lost from Lake Mead and Lake Powell and 0.9 maf from the reservoirs upstream from Powell. The total consumption for these two and a half months was 16 percent of the “benefit” of Water Year 2023.

Today, the contents of Lake Mead and Lake Powell are about the same as what they were in mid-June 2021.

“As great as this year was for precipitation, we’ve got to keep the big picture in context,” Schmidt said. “Increases in reservoir storage are small in comparison to the total loss in storage since summer 1999. We still have a lot of ground to make up.”

The best strategy for achieving a sustainable water supply for the 40 million people who rely on the Colorado River is for state and federal governments to reach new agreements to greatly reduce water use basin-wide so that any modest recovery in reservoir storage might be preserved, he said. Otherwise, gains from even record-breaking years will quickly disappear down the metaphorical drain.

“Our best hope for a secure and sustainable water supply will rely on nimble and adaptable strategies to reduce water consumption and save the gains of each wet year,” Schmidt said. “Our focus should not only be on consuming only as much water as Mother Nature provides, but also to recover some of the storage that has been lost during the last two and a half decades.”

The Center for Colorado River Studies does research to inform the management of the Colorado River and other major rivers of the American Southwest. The Future of the Colorado River Project evaluates a range of water-supply management approaches that meet water-supply security and reliability needs of the Colorado River.