With warmer temperatures arriving and becoming more consistent in coming weeks, state climatologists, water managers and irrigation district officials will be closely observing the beginning of snowmelt in the South Platte River Basin.
Simply put, a streak of unseasonably warm days could create flooding conditions along the drainage heavily damaged by September’s epic floods.
During the weekly climate webinar Tuesday hosted by the Colorado Climate Center, snowpack in the South Platte basin was reported at 138 percent of normal for this time of year.
What’s more, the South Platte’s tributary rivers – including the Big Thompson, the St. Vrain and the Cache la Poudre – have been reporting base flows of as much as 300 percent above normal. Base flows this time of year are measured before snowmelt. Those high flows are still attributable to the September floods.
“The groundwater contribution from the flooding is still working its way to the river,” assistant State Climatologist Wendy Ryan told I-News at Rocky Mountain PBS. “It’s a rule of thumb that there’s quite a lag time before all the water makes its way to the stream.”
Many irrigation districts along the South Platte sustained heavy damage in September to headgates and other infrastructure. In some places, the river changed course sufficiently for intake structures to be left high and dry.
“There are places where headgates were scoured away,” Ryan said. “Longmont is still trying to figure out what they need to do on the St. Vrain – leave it where it is or restore it to where it was.”
Many irrigation companies have made essential repairs with FEMA money and other resources, Ryan said, and they can play a valuable role in removing water from the river if flooding occurs. Some of the smaller ditch companies have not made repairs.
Meanwhile, she said, everyone is hoping that the spring warmup in the Rockies will be mellow enough to produce “a nice, well-behaved runoff.”
There are parts of the state, of course, that would like to have those kinds of worries. As of now, drought conditions are persisting into the fourth year in the southeast quadrant of the state, with the driest areas for March centered over the already drought devastated areas in Lincoln, Cheyenne and Kiowa counties, according to the climate center.
Las Animas and Baca counties are reporting less than 50 percent of average precipitation for the water year, which began last October.