Rob Roy reservoir reaches peak

The Rob Roy Reservoir about six miles southwest of Centennial in Medicine Bow National Forest can hold 11 billion gallons of water. With higher than usual snowpack melting however, a press release from the Cheyenne Board of Public Utilities (CBPU) says even that capacity will not be enough this year.

A Natural Resource Conservation Survey report on snow water equivalent (SWE) in the Lower North Platte River basin listed the amount of precipitate in the mountains at 153 percent of baseline levels May 31. On June 1, 2015, SWE levels were at 198 percent of baseline in that area, according to the report.

According to CBPU public relations specialist Dena Egenhoff, the reservoir reached full capacity in the late afternoon of May 25. Under normal circumstances, Egenhoff said that Rob Roy is fed by incoming water from Douglas Creek. With the reservoir brimming over though, the CBPU press release said that a spillway will reroute incoming water from Douglas Creek back into the creek. As of May 31, Egenhoff said that water levels in the reservoir were .60 feet above maximum.

Douglas Creek is an offshoot of the North Platte River, and with the Rob Roy Reservoir cut off as an outlet for the creek, much of that water will be backed up and flow back into the Platte. With the reservoir essentially posting a “no vacancy” sign, there is one less place for the swollen North Platte River to dump excess water load during the spring runoff.

Egenhoff stressed that much of what happens from here on is up to mother nature. “If we had a rain or snow event, we could expect to see an uptick (in water levels),” she said.

Though Egenhoff declined to estimate how long the reservoir would be at capacity, the press release from CBPU said that “flows from Douglas Creek and surrounding areas could be high for several weeks.” The press release also warned local residents and visitors that changing weather conditions could make for rapid fluctuations in water levels in the affected area. Egenhoff advised outdoor recreationists in the area to “as always, be cautious near swift or fast-moving water.”

Egenhoff said that Rob Roy also reached capacity last year, and that the reservoir had done so in every year since 2010, except for 2013.

Rob Roy is the largest of six reservoirs servicing the city of Cheyenne, and it holds 35,640 acre-feet of water when full, according to a City of Cheyenne website. Figures from that website indicate that five of the six reservoirs supplying the city were at or above capacity as of May 22. It also says that Rob Roy was already over capacity by May 22 in 2015.

The reservoir celebrates its fifty year anniversary this year.