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Colorado Water Supply Outlook Report March 1, 2014
For the majority of the state of Colorado the outlook for spring and summer water supplies is encouraging. The snowpack in the northern and central basins continues to track above normal, but the outlook for the southwest portion of the state is not as rosy. The snowpack’s in the Upper Rio Grande and the combined San Juan, Dolores, Animas, and San Miguel basins are tracking below normal as of March 1. Both major basins received beneficial moisture from snow storms in the region in early February, but conditions dried up during the latter part of the month. The March 1 streamflow forecasts follow the trends in snow accumulation across the state; above normal runoff throughout the northern and central basins, and below normal runoff forecast for the southwest portion of the state. Improvements in snowpack and streamflow forecasts are still possible for the drier regions with March typically being a big month for snow accumulation throughout the state.
Colorado has now experienced three consecutive months of above normal snowpack readings. Since January 1 the snowpack percentages have been steadily increasing each month. Reports from SNOTEL sites and manual snow courses across the state put the March 1 statewide snowpack at 116 percent of the median, up from 107 percent of median recorded on February 1. The only snowpack percentage in the state to decline this past month was in the Upper Rio Grande basin. This basin’s snowpack was just 79 percent of median as of March 1, a 5 percentage point decrease from last month’s report. All other basins saw increases in their snowpack percentages this month. The North Platte and South Platte basins had the greatest increases with gains of 18 and 25 percentage points respectively. The Gunnison basin jumped 10 percentage points to 114 percent of median and the Colorado basin gained 9 percentage points putting it at 130 percent of median. The Arkansas basin saw the smallest increase as a whole, up just 1 percentage to 109 percent of median, but the headwaters portion of the watershed gained 15 percentage points. Statewide snowpack totals are an impressive 161 percent of last year’s totals for this same date. With roughly twenty percent of the accumulation season remaining, there is still plenty of time for recovery in the southern basins if weather patterns shift favorably over the next few weeks.
February brought some impressive precipitation totals to Colorado’s high country. Statewide monthly precipitation for February was 133 percent of average. All the northern and central basins recorded well above average precipitation over the last month with totals ranging from 123 percent of average in the Gunnison basin to 209 percent of average in the South Platte basin. The Upper Rio Grande and combined San Miguel, Dolores, Animas and San Juan basins were the only basins to record below average precipitation during February. The precipitation totals for February in the San Miguel, Dolores, Animas and San Juan basins were 96 percent of average and the Upper Rio Grande basin was at just 67 percent of average which is the lowest percentage statewide. The bright side to this is that both basins recorded higher monthly percentages than they did last month. Total year-to-date precipitation for the state was up to 108 percent of average as of March 1 which is 149 percent of last year’s total precipitation at this same time.
Colorado’s reservoir storage remains just slightly below the long term average. As of the end of February reservoirs across the state were storing 90 percent of their average storage volumes. Across the major river basins, storage volumes range from 60 percent of average in the Arkansas basin to 112 percent of average in the South Platte basin. Storage across the state has increased slightly this past month. Currently the state’s reservoirs are storing 3,193,700 acre-feet of water, which is 52 percent of the capacity of the reservoirs. At this time last year Colorado’s reservoirs were at only 39 percent of capacity, storing 2,419,300 acre feet of water. While it is doubtful that all basins will be able to fill their reservoirs this season, the basins in the northern and central part of the state will have an opportunity to continue improving their storage totals with this spring and summers runoff.
Where snowpack totals are above normal, the outlook for summer water supplies are positive. The opposite is also true for areas with below normal snowpack’s. As of March 1, the highest streamflow forecasts with respect to average are for the headwaters of the Colorado River basin. All forecasts in this region are calling for well above normal April to July flows; the highest percentage is for the Inflow to Willow Creek Reservoir which predicts flows at 147 percent of average for that time period. Forecasts for the South Platte basin are also in good shape with the headwater streams predicted to flow at around 135 percent of average and the northern tributaries in the 120 percent of average range. The Upper Rio Grande and the San Juan and Animas basins currently have the lowest forecasts statewide. Streamflows in these regions are expected to be 70 to 80 percent of average for the spring and summer period. The lowest forecast percentage statewide is for Sangre de Cristo Creek in the San Luis Valley, at just 40 percent of average for the April to September period. We are still in the snow accumulation season, so expect changes to these forecasts if weather patterns change drastically over the next month.