The May 1 #Colorado Water Supply Outlook Report is hot off the presses from the NRCS

watersupplyoutlookreport05012016cover

Click here to read the report. Here’s an excerpt:

Snowpack

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Cooler mountain temperatures and increases in precipitation during April helped improve mountain snowpack throughout Colorado. Many SNOTEL sites in the South Platte, Arkansas, and combined Yampa, White, and North Platte River basins continued to accumulate snow and had yet to reach peak snowpack for the year on May 1st. Additionally, many locations in the Gunnison, Upper Rio Grande, and combined San Miguel, Dolores, Animas, and San Juan River basins, as well as low-elevation sites in the other river basins, saw delays in melt and a brief increase in snowpack amounts. Almost all of state’s river basins experienced increases in percent of normal snowpack compared to last month. The Arkansas had the greatest improvement in snowpack with respect to normal, shifting from 92 percent on April 1st to 110 percent of median on May 1st. The Gunnison River basin also saw a substantial improvement upward to normal conditions and is now at 100 percent of the median. The South Platte, combined Yampa-White-North Platte, and Upper Colorado River basins have the healthiest snowpack with respect to normal at 114, 113, and 112 percent respectively. The Upper Rio Grande was the only major River basin that did not experience an improvement in snowpack percent of normal since last month. Additionally, despite the snowpack additions at many SNOTEL sites, the Upper Rio Grande and the combined southern river basins remain the only basins that have a below normal snowpack and are at only 77 percent and 85 percent of median snowpack respectively. These basins did not reach typical peak snowpack accumulations, so less than normal snowpack will be available to contribute to runoff this spring and summer…

Precipitation

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An active weather pattern delivered abundant precipitation across Colorado during the latter half of April. Unlike many of the previous storms that favored the northern portion of the state this winter, the precipitation events during April were beneficial for all of the major river basins. Most basins accumulated precipitation that was well above normal for the month and statewide April precipitation was 110 percent of average. The Arkansas River basin experienced the greatest precipitation amounts with respect to normal at 142 percent of average. The Upper Rio Grande also had a good April and accumulated 122 percent of normal precipitation for the month. This comes as a welcome change as both of these basins have had precipitation much below normal since December. The combined San Miguel, Dolores, Animas, and San Juan was the only major river basin that did not receive above normal precipitation during April, yet still received 91 percent of average precipitation for the month. Moisture received during April helped all the major basins maintain near to above normal water year-to-date precipitation. Statewide, accumulated precipitation for the water year continues to track with normal conditions and is currently at 100 percent of average…

Reservoir Storage

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End of April storage for the majority of Colorado’s reservoirs is near or above normal, which has provided another boost in percent of normal for the state, increasing statewide storage to 112 percent of average. The percent of average storage has been climbing steadily during the 2016 water year for reservoirs in the Gunnison, Upper Colorado, and combined San Miguel, Dolores, Animas, and San Juan River basins and this trend continued during April with these basins rounding out the month at 117, 115, and 106 percent of average respectively. Collective reservoir storage in the South Platte River basin also increased slightly from 107 to 108 percent of average. The Arkansas River basin held steady at 120 percent of average storage and now has the highest percent of average out of the major river basins. The Upper Rio Grande basin experienced its first drop in percent of normal this water year from 94 to 91 percent of average, but is still substantially better than last year when it was 76 percent of average at this time. The combined Yampa, White, North Platte River basin also experienced a drop in percent of normal from last month, down from 120 to 115 percent of average. This drop in reservoir storage likely reflects the abundant snowpack in this basin, as reservoir operators adjust reservoir levels in anticipation of an above normal runoff season…

Streamflow

streamflow05012016

The water budget of Colorado, as well as that of the downstream states, depends heavily on April mountain precipitation. This year April produced near normal precipitation across much of the state, but last year was a different story as was stated in the May 1, 2015 Colorado Water Supply Outlook Report, “The majority of Colorado‘s streams are expected to produce roughly 50 to 70 percent of average streamflow volumes”. This year’s forecasted streamflows are predicted to surpass last year’s forecasts in most locations by a large margin. The majority of this year’s streamflows across Colorado are projected to be between 70 and 112 percent of normal. The lower forecasted volumes in the state are mainly in the San Juan, northwestern and southern Rio Grande, and parts of the Gunnison River basins. Generally these forecasts range from 70 to 85 percent of normal, yet are far better than this time last year. Farther north and east in Colorado, projections range from 85 to 112 percent of normal, in some cases above 112 percent of normal where considerable precipitation fell over the last few weeks in areas such as Bear Creek near Evergreen, Willow Creek Reservoir Inflow, and Boulder Creek near Orodell. Although most forecast values are often consistent with others in the greater watershed, forecasts can vary more than would be expected. Therefore, be sure to reference specific forecast points of interest for the most accurate projections. Also note that confidence in a given forecast, or forecast skill, can often be indicated by the spread of the exceedance forecasts. A large range between the 90 and 10 percent forecasts can indicate lower skill than a smaller range between these forecasts. A large factor that plays into this forecast skill is future precipitation, which can be highly variable this time of year…

From The Denver Post (Jason Blevins):

The latest report from the Natural Resources Conservation Service’s Colorado Snow Survey shows April snowstorms bolstered the state’s snowpack by 7 percent, pushing the snowpack statewide to 104 percent of normal and marking the first month-over-month improvement in 2016…

All seven of Colorado’s major river basins harvested 90 percent of normal April precipitation or better last month. Conditions were worse heading into April, but the heavy moisture that fell in the latter half of the month reversed what was looking to be a lean spring melt.

Measurements from the state’s mountain top stations show that the North Platte and South Platte river basins have the deepest snowpack in the state, at 114 percent of normal. The Arkansas River basin logged the most improvement in April, while the less robust southern basins of the San Miguel, Dolores, Animas and San Juan saw little change.

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