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The heat is on River’s up, snowpack’s down

Rafters and kayakers with an eye toward running Colorado rivers and creeks should exercise extreme caution right now, as many statewide waterways are running at or near unprecedented levels.

According to the United States Geological Survey, the San Juan River through Pagosa Springs peaked at more than 2,900 cubic feet per second (cfs) around midnight, May 30. Peak flows quickly fell to about 1,650 cfs by late last Thursday, but rose again with the onset of unseasonably warm weather over the past weekend. By late Sunday night, the river rose to more than 2,400 cfs.

Though San Juan flows are now dropping, the river’s volume is still well above the seasonal norm and boaters should be extra cautious while negotiating its various reaches.

Across the state, meanwhile, rivers like the Big Thompson, the Eagle and Gore Creek are overflowing their banks, while causing some flooding and significant property damage. Authorities in those areas have advised boaters to think twice before running rivers at all, until flows moderate somewhat.

The Natural Resources Conservation Service (NRCS) attributes the state’s sudden high water to rapid runoff brought on by warm, dry weather across Colorado. By June 1, in fact, the statewide snowpack had fallen to just 53 percent of average, after measuring 78 percent of average a month earlier. In the combined San Juan, Animas, Dolores basin, the June 1 snowpack measured just 19 percent of average — by far the lowest in the state.

According to NRCS State Conservationist Allen Green, southern Colorado experienced the greatest snowpack decline through May.

“A general lack of precipitation since early April has decreased the outlook for runoff in the southwestern corner of Colorado,” Green said in an NRCS monthly snowpack report. “What appeared to be an excellent runoff season back in mid-winter has deteriorated into a below average runoff season in the Animas, Dolores and San Miguel rivers.”

Late spring storms, meanwhile, improved conditions up north, where cooler, moist weather enhanced and maintained the late-season snowpack and greatly improved the summer water supply outlook.

“While runoff forecasts remain below average in these (the northern) basins,” Green added, “these increases have translated into an excellent recovery from the early winter conditions where runoff was expected to be well below average. With the majority of annual surface water supplies originating from the melting mountain snowpack, these trends are closely watched by water managers across the state.”

Even as regional snowpacks and relative runoff predictions are less than favorable, the state’s water storage appears in good shape. According to the NRCS monthly report, the season’s rapidly melting snowpack has resulted in above-average storage in most Colorado reservoirs.

Statewide, the June 1 reservoir storage was listed as 110 percent of average, with only the Rio Grande basin showing somewhat less than 100 percent of average storage. Thankfully, the combined San Juan, Animas, Dolores basin tops the list at 115 percent of average. The Gunnison, Colorado and Yampa basins were only slightly lower.

With adequate water storage in place, Colorado water users should fare well during this year’s growing season. And for now, rafters and kayakers are blessed with exhilarating flows, though their season might fall short as the remaining high-country snowpack disappears fast.

As for Colorado’s high-country stream fishing, only time will tell what conditions lie ahead. Currently, flows are too high and roiled to offer viable options, while summer’s seasonal low flows might well be too low to adequately safeguard healthy trout populations.

Perhaps, summer monsoon rains will afford real relief … as they often do.

chuck@pagosasun.com