Lake Powell runoff to hit record low, putting Arizona's water supplies at risk

The past winter brought record-low snowpack in the mountains of Colorado, Utah and Wyoming that feed the Colorado. March brought record heat that caused the snows that had fallen to melt prematurely. 

The result is that runoff from the melting snow into the river will bring April through July flows into Powell to only 13% of average, says the federal Colorado Basin River Forecast Center, a division of the National Oceanic and Atmospheric Administration.

That would make the spring-summer runoff into Powell the lowest of its kind since Lake Powell was created in 1963 by the construction of Glen Canyon Dam.

The total amount of water expected to reach Powell is 800,000 acre-feet from April through July.

That's the equivalent of enough water to serve all Tucson Water customers for eight years. But it's a far cry from what Arizona, California and Nevada have come to expect from Lake Powell during these crucial months. Powell stores water for future shipment to Lake Mead, which delivers the water to those three states and Mexico.

This year's expected total runoff is also 42% lower than the forecast for April-July flows into Powell that the agency issued only a month ago. It's 17% less than the previous low-flow record for spring-summer flows, set in 2002.

"No one should be surprised with this forecast. The only question is whether it will be the driest or second driest on record. We won’t know for sure until July, but right now it looks like it will be the driest runoff" on record, said Eric Kuhn, a longtime water researcher and author based in Glenwood Springs, Colorado, who closely tracks river flows.

The effect of the expected low flow into the river on water users in the seven Colorado River Basin states is unknown now.

That's because there is a crosscurrent right now of pending proposals and a federal action that could significantly alter how much river water is actually available this year to the cities and farms that use it, including Tucson and Phoenix.

But in general, "it’s going to be awful for the water users in the basin," Kuhn said.

For one, the U.S. Bureau of Reclamation will soon start significantly cutting its annual river water release from Lake Powell at the Arizona-Utah boundary to Lake Mead at the Arizona-Nevada boundary to keep Powell from falling too low.

Second, the states of Arizona, California and Nevada have just this past week proposed to the feds to cut their own uses of the river water by 700,000 to 1 million acre-feet through 2028.

Third, the bureau this summer is also expected to decide on a long-term plan for reducing overall river water use, again to protect Powell and other reservoirs from falling too low.

But if the weather doesn't improve in the coming year, Kuhn and many other water experts have said that next year, a true water crisis could develop in the basin in which water agencies may have trouble obtaining river water to meet their customers' demands.

An expected, a record-setting El Niño season this coming fall and winter could improve the basin's water outlook with heavy storms, but there's no certainty that will happen, many forecasters have said. The El Niño weather phenomenon, featuring abnormally warm Pacific waters, usually results in wetter winters in the southern U.S. 

In recounting the warm, dry winter that triggered the expected record low river flows, the river forecast center cited an early April federal snow survey for Utah that said, “At no time since systematic snowpack measurements began around 1930 has April 1 snowpack been this low in the state of Utah."

A similar analysis performed in early April by the Colorado Climate Center concluded that “this has been the worst year for Colorado snowpack in recorded history, and most locations have less than half of the previous record low."

In April, the region got more precipitation that led to modest snow accumulation and reduced snowmelt rates due to cooler and cloudier weather, the forecast center said.

But as of May 1, the amount of water in existing snowpack — a key indicator of what's available for river runoff — remained at historic lows. The amount of water in snow remains at 30% of normal levels in Utah, Wyoming and Colorado, the forecast center said.

Looking ahead, forecasters expect warm, dry weather through next Wednesday, followed by an 8-14 day period of warmer-than-normal temperatures but precipitation levels at or above normal across the Southwest and most of the Rockies.