Snowpack means little at reservoir
Local water managers note South Platte Basin at 110% of average, still short of ‘peak median’
Recent snowstorms in the western two-thirds of Colorado will improve the state’s water situation, especially in the Colorado River Basin, but may not mean much to irrigators in the South Platte Valley.
According to a recent article in Fresh Water News, snowpack is above average at 109% of the historic norm. The article quotes Bruno Rodriguez, a meteorologist at the National Weather Service station in Boulder, saying that snowfall amounts have been quite healthy, especially east of the Continental Divide and into the I-25 corridor.
“East of the divide, it was … significantly more impactful and significantly more snowfall than any of the previous storms this season,” Rodriguez said.
The storms also covered the season’s dust-on-snow events, which can hasten snowmelt and leave water users and rivers in short supply in late summer.
While that’s good news, it won’t have much impact on the reservoirs in northeast Colorado. Jim Yahn, manager of North Sterling and Prewitt reservoirs, said those fill during the winter months, so spring runoff isn’t a big factor for them.
“Because they are off stream reservoirs with relatively small inlet ditches, (they) need to fill when water is available,” Yahn said. “We as reservoir managers can’t wait to see whether there is going to be enough snowpack so that we can fill later and leave room in the reservoir for that runoff. When there is water in the river we fill as soon as possible.”
Filling whenever possible ensures the reservoirs are as full as possible at the beginning of the irrigation season and allows irrigators with more junior recharge rights to store water underground, shoring up their well augmentation supplies.
Yahn said that the level of snowpack in the South Platte
Basin, while seemingly plentiful at 110 percent of median, is only 83 percent of peak median, or the average peak snowpack.
“We still need about three more inches of moisture in the form of snow to reach average peak,” he said.
How much good the snowpack does downriver also depends on weather conditions between now and midsummer. Yahn said he has seen years of above average snowpack resulting in very little runoff and years of low snowpack ending up with long, healthy runoff because of cool weather and late spring rains.