Be prepared for some of the West’s biggest and most important rivers and streams to see record low flows this spring and summer.
That’s the message of the Colorado Basin River Forecast Center’s latest water supply forecast released Monday.
“Below average precipitation continued to be the norm and not the exception for the month of January,” the forecast report reads. “January marks the fourth consecutive month of the 2018 water year with widespread below average precipitation.”
The center’s forecasters are projecting the flows into Lake Powell — one of the largest human-made lakes in the country — to be 47 percent of average. The lake, on the Utah-Arizona border, is part of a reservoir system that supplies water to some 40 million people in the southwest. As of early February Lake Powell was at 56 percent of full capacity, while its sister reservoir, Lake Mead, was at 41 percent of full capacity.
The news is worse in the Colorado River’s lower basin, which includes Arizona, and portions of New Mexico and Nevada. In those states, spring runoff from February to May is projected to be be less than 30 percent of median.
The lowest water supply forecasts in the Upper Colorado River include the Dolores and San Juan Rivers in southwest Colorado, and across central and southern Utah including the Virgin, Sevier, and San Rafael River Basins.
Parts of the southern Rocky Mountains are currently experiencing the warmest and driest winter on record. Snowpack eventually turns into the region’s water supply, and without it, rivers and streams suffer. Snow measurement sites in southern Colorado, central Utah, and Arizona are reporting their lowest levels on record.
The Salt Lake City-based center is within the National Oceanic and Atmospheric Administration and releases monthly forecasts during the winter so water managers, farmers and recreationalists get a sense of how winter snowpack is shaping up, and what spring runoff could bring.
Last year’s above-average snowfall in the southern Rockies boosted reservoir levels throughout the region giving water managers some buffer to withstand a dry year, with both Arizona and New Mexico being the exception. Those two states are currently reporting below average reservoir storage.
This story is part of a project covering the Colorado River, produced by KUNC and supported through a Walton Family Foundation grant. KUNC is solely responsible for its editorial content.