From The Mountain Mail (Brian McCabe):
After a dry October and early November, the 2020 water year has been mixed for Colorado.
As of Feb. 1, statewide snowpack was up, at 109 percent of median, while year-to-date precipitation is at 88 percent.
However, much of the state has been hit by several storms in the past few days, which have not yet been taken into account.
“After a particularly dry late summer and fall, December provided substantial snow accumulation in Colorado,” Karl Wetlaufer, Natural Resources Conservation Service hydrologist, said. “January then followed with mostly below average precipitation, with southern Colorado being the driest, an area that received the most accumulation in December.”
That means while snowpack is above normal across the state, the precipitation deficit has led to streamflow forecasts below average statewide.
Currently Colorado is at about two-thirds of its normal peak snowpack in mid-April.
Reservoir storage across the state has dropped throughout the water year on average, but not across the board, with some reservoirs up while others are down.
Statewide, reservoir storage is at 105 percent of average, with only the Arkansas and Rio Grande basins below 100 percent, at 96 and 85, respectively.
However, the state average is 83 percent compared to last year’s percentage of average reservoir storage, with South Platte and Yampa/White basins at 104 and 103 percent.
The combined San Miguel, Dolores, Animas and San Juan Basins are lowest at 57 percent.
The Arkansas Basin, South Platte River and combined Yampa and White river basins, where the average of forecast values is 96, 97 and 98 percent of normal, have the most plentiful water supply forecasts, with outlooks for spring and summer streamflows to be close to average.
Snowpack in the Arkansas Basin is above normal at 119 percent, tied with the South Platte Basin as highest in the state.
Precipitation for January, however, was 62 percent of average, bringing water year-to-date precipitation to 87 percent of average.
The Upper Arkansas Basin is currently at 130 percent of median and 123 percent of last year’s median. Last year saw a lot of precipitation in late winter and early spring months.
The Cucharas and Huerfano sub-basin is at 97 percent of median, the Apishapa sub-basin is at 89 percent, and the Purgatoire sub-basin is at 105 percent.
Reservoir storage at the end of December was 96 percent of average, compared to 89 percent last year for the Arkansas Basin.