Forecasters predicting lower than average runoff | PostIndependent.com

Forecasters predicting lower than average runoff

Dan Ben-Horin
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Now that winter is mostly behind us, it’s time to look at our snowpack and make some estimates of what spring runoff may actually look like. The National Weather Service’s Climate Prediction Center (CPC) has forecasted an increased chance for above average precipitation for the entire Upper Colorado River Basin, which is expected given the existing El Niño conditions.

Last year, Miracle May gave our reservoirs a giant boost. Whether that will happen again is still difficult to determine. Recent rains have been a welcome occurrence for the drought-starved Southwestern U.S.: As of May 1, the Colorado snowpack was 111 percent of average. The CPC further reports no signs of any drought development over the next three months and has recommended the removal of the official drought status in the southeastern part of the state.

Over the next month and a half, the Colorado River Water Conservation District will be holding its annual State of the River meetings throughout the Upper Colorado River Basin. Meetings will be held here in Garfield County, as well as in Summit, Mesa, Grand, Eagle and Delta counties. These meetings provide an opportunity for water experts to sketch out how this winter’s snowpack will translate to spring runoff volume and reservoir levels both locally and downstream. With these meetings still a few weeks away, here are some predictions for the larger reservoirs in the Upper Colorado River Basin from the U.S. Bureau of Reclamation:

• Blue Mesa Reservoir: The March flow into Blue Mesa was at 177 percent of average, but forecast inflows over the next three months are all projected to be lower than average, with volumes of 71 percent, 73 percent and 82 percent of average for April, May and June, respectively.

• Flaming Gorge Reservoir: Flaming Gorge saw an inflow at 83 percent of average for the month of March, and inflows for the months of April, May and June are all forecast to be below average, with volumes projected to be 82 percent, 71 percent and 77 percent respectively.

• Navajo Reservoir: March inflow into Navajo was at 90 percent of average. Inflows for the next three months are projected to be below average, with April, May and June forecasted inflow volumes of 70 percent, 79 percent and 72 percent of average, respectively.

• Fontenelle Reservoir: March inflows at Fontenelle on the Green River in southwestern Wyoming totaled 50,000 acre-feet (AF), or 95 percent of the historic average. Daily inflow averages are on the rise with the beginning of spring runoff, with a seven-day average of 1,330 cubic feet per second as of April 14. The Colorado Basin River Forecast Center predicts spring inflows all to be below average. April, May and June forecasted inflow volumes are 82 percent, 67 percent and 84 percent of average respectively.

• Lake Powell: In March, the flow into Lake Powell totaled 553,000 acre-feet, or 83 percent of average. The reservoir elevation is close to the projected seasonal low, and will soon begin increasing as spring runoff enters the reservoir. The April to July 2016 water supply forecast for Lake Powell projects that the most probable inflow volume will be 5.3 million AF, or 74 percent of average. There is much variability in the forecast water supply for the season, with predictions ranging from 3.85 million AF (54 percent of average) to 7.65 million AF (107 percent of average).

While much of the forecasted inflows in the Upper Colorado River Basin are below average, there is still much uncertainty about what the next few months will actually produce. These data come from a report from the Bureau of Reclamation from mid-April, and we are now in a cycle of above normal precipitation. Let’s keep our fingers crossed that this cycle continues well into the spring, swelling our rivers with some much-needed relief for the Southwestern U.S., and putting our Gore-Tex jackets to good use.

Dan Ben-Horin is a watershed specialist with the Middle Colorado Watershed Council. His column, Your Watershed, appears on the second Sunday of each month. The council works to evaluate, protect and enhance the health of the Middle Colorado River Watershed through the cooperative effort of watershed stakeholders. To learn more, go to http://www.midcowatershed.org.


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