#Snowpack #Runoff news: Water Supply Outlook for Colorado and Downstream States Improves — NRCS

Here’s the release from the Natural Resources Conservation Service (Brian Domonkos):

For the first time during 2016, statewide snowpack improved over the previous month as opposed to the declines that have occurred each month since January 1st. April weather conditions yielded a seven percent improvement in snowpack, which now stands at 104 percent of normal. Mountain precipitation across the state of Colorado during April was the best of the 2016 calendar year, at 110 percent of normal. Now water year-to-date precipitation is exactly at 100 percent of normal. Brian Domonkos, Colorado Snow Survey Supervisor, illustrates how fortunate the Colorado water situation is, “At this time last year the water supply outlook was grim at best. Colorado’s current snowpack and precipitation levels are right where we want to be this time of year. Elsewhere in the Western United States seasonal snowpack during 2016 succumbed to early spring warming and did not recover as Colorado did from recent storms.”

snowpacksummarymap05012016

The seven major mountain watersheds in Colorado all received 90 percent of normal April precipitation or better. Special mention is warranted in the Arkansas, Upper Rio Grande and combined Yampa, White and North Platte Basins, because these areas received 120 percent of normal or better precipitation. The seven major watersheds also have ninety percent of normal or better water year-to- date precipitation.

Snowpack metrics indicate that the North and South Platte River basins have the best snowpack in the state at 114 percent of normal. The Arkansas saw the greatest improvement in April, while the Upper Rio Grande and combined San Miguel, Dolores, Animas and San Juan Basins saw little change. It is fortunate those basins saw little change downward given that snowpack there is now 77 and 85 percent of normal respectively. Although not reflected in snowpack values, it is also fortunate that rain was abundant most particularly in the Upper Rio Grande, which added to the greater water budget.

Statewide reservoir totals increased one percent since April 1st ending the month at 112 percent of normal, with declines occurring in the Rio Grande, Arkansas and combined Yampa, White and North Platte watersheds.

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For more detailed information about individual Colorado watersheds or supporting water supply related information, have a look at the Colorado Water Supply Outlook Report or feel free to go to the Colorado Snow Survey website at:

http://www.nrcs.usda.gov/wps/portal/nrcs/main/co/snow/

Or contact Brian Domonkos, Colorado Snow Survey Supervisor at Brian.Domonkos@mt.usda.gov or 720-544-2852.

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

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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

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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.

#Snowpack #Runoff news: ~Average dust on snow season — 6 events

Click on a thumbnail graphic to view a gallery of snowpack data from the Natural Resources Conservation Service.

From The Denver Post (Jason Blevins):

The lack of dust — at least on Colorado’s central and northern mountains — removes one capricious ingredient from the always tricky formula of forecasting runoff.

“Many factors impact the timing and flow of spring runoff, including soil moisture, snowpack, weather, dust on snow and solar radiation. Given all the variables that play a role, we’d hesitate to say that the lack of dust makes it easier to predict runoff,” Denver Water spokeswoman Stacy Chesney said. “The lack of dust on snow benefits water managers because, all other variables held constant, it means a slower and more predictable melting of the snowpack.”

It takes careful coordination to fill all 19 of Denver Water’s reservoirs, a balancing act that weighs a range of inflows, water rights, customer demands and projects, all influenced by dust, weather, snowpack, soil moisture and sunshine. Sometimes, water managers release water to make room for a surge of snowmelt.

Strong snowpacks in the South Platte Basin in recent years, combined with increased conservation by Front Range users in 2014, meant Denver Water diverted the least amount of Western Slope water through the Roberts Tunnel beneath Dillon Reservoir since it opened in 1963. Last year, also one of very low dust, Denver Water diverted the second-least amount since the tunnel opened.

Snow researchers in southern Colorado for 13 years have studied the red dust swirled onto the snowpack from the Colorado Plateau.

The Colorado Dust on Snow Program was launched up Red Mountain Pass outside Silverton in 2003, where researchers with the Center for Snow and Avalanche Studies had started noting stronger dust storms laminating the San Juans in a pink patina of sun-sucking dust. When the spring sun began melting the snowpack, those dust layers would collapse on top of one another, creating a dark blanket that absorbed sunshine and hastened snowmelt from a slow trickle into a sudden surge.

By 2008, the dust-on-snow researchers were studying snowpacks atop a dozen Colorado mountain passes, compiling data that now are essential tools for water managers tasked with corralling as much of Colorado’s own water before it rushes downstream to other users.

They measured three dust storms the first year. There have been big years, with as many as 12 dust events: 2008-09 and 2011-12. And there were years with only three: 2003-04 and 2014-15.

This winter was about average, with six dust events and most of them relatively small. Most interesting this year was the lack of dust accumulation on Berthoud, Loveland and Rabbit Ears passes.