This is the time of year that the Natural Resources Conservation Service’s Basin Outlook Reports are the talk of the town. Here’s the link to the March 1, 2012 Colorado Basin Outlook Report. Click on the thumbnail graphic to the right for the streamflow forecast map from the report. Here’s the introduction to the report:
Summary
The month of February brought improvements to snowpack percentages in all major basins in Colorado. Unfortunately the snowy month was not enough to boost the snowpack to average conditions; as of March 1 the state snowpack was at just 81 percent of average. With only four to six weeks remaining in the typical accumulation season the odds of the snowpack obtaining average conditions are diminishing. Runoff forecasts remain below average across the state, with slight improvements over last month in the northern and southwest portions of the state. A majority of basins have considerably dry soils beneath the snowpack which can reduce surface water supply. Thanks in part to a good water supply year in 2011 reservoir storage volumes for the state are currently at 107 percent of average.
Snowpack
Despite above average snow accumulation during the month of February the statewide snowpack remains below average. The good news is that last month’s snowfall was very beneficial to the Yampa, White and North Platte basins. These basin’s snowpacks have been well below average for the entire season and previously reported just 65 percent of average conditions on February 1. As of March 1 the basins snowpack percentages had improved to 78 percent of average. The combined San Juan, Animas, Dolores, and San Miguel basins also benefited from above average snowfall in February. These basins saw a snowpack increase from 73 percent of average on February 1 to 86 percent of average measured on March 1. Across the rest of the state snowpack improvements were more nominal. The South Platte basins’ snowpack increased 8 percentage points over the last month from 81 percent on February 1 to 89 percent of average on March 1. In the Gunnison, Colorado, Arkansas and Upper Rio Grande basins only slight increases in snowpack percentages were measured compared to last month’s readings. For the state overall, the March 1 snowpack was reported at 81 percent of average, this is only 71 percent of last year’s readings at this same time. Comparisons to last year show indicate that the current snowpack is well below last year’s readings for all basins except for the Rio Grande and the combined basins in the southwest.
PrecipitationMountain precipitation measured at SNOTEL sites across Colorado during the month of February was near to well above average. Statewide monthly totals were at 111 percent of average, marking a welcome turn in conditions after three consecutive months with below average precipitation measured. The Arkansas and Colorado basins were the only basins in the state to post below average monthly precipitation totals; still each basin reported a respectable 92 percent of average for the month. While February brought above average precipitation, water year totals are still below average for most basins. Year to date precipitation totals now range from just 80 percent of average in the Colorado basin to 103 percent of average in the Upper Rio Grande basin. The Upper Rio Grande and the combined San Miguel, Dolores, Animas, and San Juan basins are the only basins in the state with above average water year precipitation totals. Statewide year to date precipitation was at 90 percent of average at the close of February. Without the wet month of October and the return to above average conditions this past month, water year totals would be quite dismal.
Reservoir Storage
End of February storage data from the state’s major reservoirs indicates that volumes increased slightly during the past month. Statewide, storage is at 107 percent of average and there are a total of 3,588,000 acre feet of water available in the state’s reservoirs. Only two basins, the Upper Rio Grande and the Arkansas have below average storage volumes as of March 1. The lowest percentage in the state, at 69 percent of average, was reported in the Upper Rio Grande, this basin has had well below average storage volumes since the beginning of the water year. The highest storage amounts, as a percent of average, were reported in the Yampa basin which was 124 percent of average on March 1. Strictly looking at total volumes, the Colorado basin is storing the largest volumes above the average for this time of year with 117,000 acre feet greater than average stored as of March 1. Statewide storage on March 1 was 102 percent of last year’s storage amounts on this same date. This equates to an additional 56,000 acre feet of water compared to last year’s levels. Once again, the good storage volumes across most of the state will most certainly aid those water users who face potential surface water shortages this summer.
Streamflow
Below average streamflow runoff is expected this spring and summer across the state of Colorado. Outlooks for the northwest and southwest portions of the state have improved in the past month thanks to above average snowfall. Elsewhere forecasts remained consistent with those issued on February 1. Currently, the lowest forecasts in the state occur in the headwater tributaries to the Gunnison and South Platte rivers. Most of these forecasts range from 60 to 75 percent of average. March 1 forecasts for most of the rest of the state generally range from 75 to 85 percent of average. Volumes in this range are expected to prevail throughout the Yampa, White, Colorado, and combined San Juan, Animas, Dolores and San Miguel basins. The lower portion of the South Platte and the northeastern portion of the Rio Grande are in slightly better shape with forecasts ranging from 80 to 95 percent of average at most locations.