Implications Dire for Summer Water Users
WESTERN COLORADO – Knee deep. Ankle deep. Hip deep.
Skiers, and ski areas, talk about snow in terms of inches on the ground, storm totals, base depths.
Water managers care only about the snow-water equivalent – what snow hydrologist Mark Rikkers calls the “snow bank.” How much water is up in the high country that can be counted on to flow into rivers, irrigate crops, fill reservoirs and recharge watersheds?
They measure the water stored in snow by river basin: the Upper Colorado River Basin, the Gunnison, the Dolores/San Miguel, the Yampa/White. And so far this water season the numbers aren’t looking great. “Pray for a good monsoon,” said Tri-County Water Conservancy District General Manager Mike Berry recently. “If we don’t have a wet spring, and rain in July and August, we’re going to be in trouble.”
Tri-County manages nearly all the water in the Ridgway Reservoir.
Right now, according to Phyllis Ann Philipps, the Colorado State Conservationist with the Natural Resources Conservation Service, the state has only received 73 percent of average snowfall (averaged for the last 30 years). And that number is just 83 percent of last year’s snowpack, as of March 1.
Reservoir storage statewide is at 71 percent of average, and 67 percent of the levels recorded last year. Reservoir levels were higher last spring after a snowy 2011, but many had to be drawn down significantly during the dry spring and summer of 2012. Berry estimated it would take springtime snow and rain (from now until the beginning of irrigation season) on the order of 130-140 percent of average in order to “bring us up to 100 percent.”
The southwest region is actually doing better than some other parts of the state. The combined San Miguel, Dolores, Animas and San Juan basins, as of March 1, have 83 percent of their normal snowpack. The big Eastern Slope basins, the Arkansas, South Platte and North Platte, are averaging 70 percent of normal between them. And normal, according to Rikkers (and corroborated by Berry) is changing. Every year, the 30-year average drops the oldest-year data and moves ahead one year. And as the climate is warming and drying, the average is warming and drying too. So, our 83 percent is relative to the average since 1983. Old timers will remember decades when “average” was considerably wetter.
According to the Colorado Basin River Forecast Center, which forecasts streamflows into the coming summer, the San Miguel River, at Placerville, is expected to have 66 percent of its normal streamflow for the period April 1-July 31. The Uncompahgre River, at the Ridgway Reservoir, has the same forecast, 66 percent. Forecasters are predicting the Gunnison River at Blue Mesa will only see 53 percent of average flow. And the Colorado River at Glenwood Springs may only have 60 percent of its average flow. (The Colorado at Glen Canyon Dam is forecast to be just 47 percent of average.)
Streamflow affects irrigation, or course. It also affects recreation, boating and fishing.
Currently, the Ridgway Reservoir is holding at 79 percent of normal storage, 66 percent of where it was at this time last year. Still, this is better than some surrounding water storage numbers: Blue Mesa at 68 percent of average (40 percent of capacity), Paonia at 30 percent of average (8 percent of capacity), McPhee Reservoir at 69 percent of average (50 percent of capacity). Way downstream, Lake Powell is holding less than half its capacity.
“If senior water rights holders put a call on the river right at the beginning of irrigation season,” Berry said, “the [Ridgway] reservoir will never fill.”
How does he know?
Eighteen snowpack telemetry sites, known as Snotel sites, dot the Dolores, San Miguel, Uncompahgre, Animas and San Juan river basins, including at Red Mountain Pass, Idarado, Lizard Head and Lone Cone. They are there to measure snow depth (with sonic sensors) and more importantly, snow-water equivalent (SWE).
There are 750 Snotel sites around the west operated by the NRCS. According to longtime snowviewer Jerry Roberts, they are “big waterbeds filled with antifreeze and a pressure gauge to measure the percent of H2O in the snow. They bounce the data off the meteorite belt that circles the earth to Portland, Oregon, then [it] magically shows up on the internet and your confuser.” (Google Snotel for the daily numbers.)
You can find the SWE yourself with the right tools, measuring the weight of a column of snow. Twelve inches of light powder might yield one inch of water. A denser foot of snow might contain three times as much water.
Using Snotel and other sites, Berry and his water superintendent calculate that the Uncompahgre River Basin contains about 67,000 acre feet of water as of March 1. Average is somewhere around 100,000 acre-feet. “It’s difficult to project that number exactly, but that’s our best guess,” he said. “Typically, about 20,000 acre-feet ‘disappear’ through evaporation, absorption by dry soils, wind, and upstream users.
“The reservoir holds 84,400 acre-feet. At 66 percent full, we have 58,000 acre-feet of water, including the dead pool [water in the deepest part of the lake, below the outflow] and the inactive pool [water that must be saved for river health and recreation]. That subtracts 25,000 acre-feet. So, we have about 33,000 acre-feet left we can use.”
Berry declined to say if that will be enough for all of the users, upstream and down.
Last year was tough on everybody, as senior water users downstream put calls on the water, drying ditches upstream, as well causing consternation, if not outright water shortages, in the municipalities of Ridgway and Ouray.
Meanwhile the drought continues. “We’re going on the 10, 11, 12-year range,” Berry said. “Our last wet period was in the late 1990s.
“It’s going to be years ’til we come out of this. Pray for rain.”