‘Every El Niño is different’
March snowfall across the Colorado mountains helped maintain the statewide snowpack near average for the water year to-date, but the strong El Niño hasn’t played out as expected.
Instead of boosting moisture in the southwestern corner of Colorado, this year’s edition of the Pacific Ocean warm-water cycle sent the storm track surging into the Pacific Northwest and then down across Colorado’s northern mountains. Northeastern Colorado has been the wettest of all, with a wide section of the plains seeing up to double the average annual rainfall so far.
That’s bad news for the Southwest, where moisture has been sparse for the past several years. Western New Mexico, most of Arizona and the southern California deserts and coast have been especially dry since the start of the rainy season. Regionally, snowpack in the Colorado River Basin above Lake Powell was 94 percent of average as of March 17, and the Federal Bureau of Reclamation is projecting that the inflow to Lake Powell will be just 80 percent of average for the April to July period.
In Colorado, the statewide snowpack was at 98 percent of average as of April 1, according to the latest report from the USDA Natural Resources Conservation Service. The Gunnison, Arkansas, Rio Grande and San Miguel, Dolores, Animas and San Juan basins snowpack didn’t get much new snow during the month and warm temperatures even spurred early snowmelt across lower elevations, where the snowpack dwindled to below normal, according to the NRCS.
In the Colorado, Yampa, White, North and South Platte River basins, the snowpack as of April 1 was average to slightly above average.
“Snowpack improved markedly in the North Platte, Colorado River and Cache La Poudre River basins with increases of 17 percent or more in these watersheds,” said Brian Domonkos, Colorado snow survey supervisor for the NRCS.
“Unfortunately, some southern watersheds saw proportionate decreases in snowpack levels – the greater Arkansas, Rio Grande, San Miguel, Dolores, Animas and San Juan basins averaged nearly a 17 percent decrease in percent of median snowpack,” Domonkos said.
Cumulative reservoir storage for Colorado has increased only minimally since last month and decreased as much as 4 percent in the Arkansas River watershed.
According to Domonkos, Colorado’s snowpack generally peaks around April 1, though the past few years have seen significant exceptions to that rule, with late season storms adding moisture.
Streamflow predictions are varied throughout the state. In general, water users and planners in southern basins should start to expect 60 to 90 percent of normal runoff, while those in northern basins should expect 85 to 105 percent of normal runoff.