Rising temps in Roaring Fork River cast shadow over fishery
July 18, 2013
GLENWOOD SPRINGS — Rising water temperatures in the lower Roaring Fork River is cause for concern for the health of the local fish population, but so far aren't to the trigger point for fishing closures, according to the state's lead aquatic biologist for the area.
Recent gauge readings on the Roaring Fork at Glenwood Springs have spiked as high as 71.5 degrees Fahrenheit during the heat of the day, said Sherman Hebein, senior aquatic biologist for the Colorado Division of Parks and Wildlife Northwest Region.
The CPW monitors stream temperatures at different points along the Roaring Fork and Colorado rivers, called thermographs, which record temperatures every 15 minutes.
Daytime temps on the Roaring Fork at Glenwood have consistently been around 70 degrees, Hebein said, with water temperatures dropping to 68 degrees at night. The Colorado River through Glenwood Springs has rarely dropped below 69.5 degrees of late, he said.
State wildlife officials have the authority to impose emergency fishing closures on stretches of river where the maximum water temperature exceeds 74 degrees at any time, or has an average daily reading of 72 degrees.
"Our concern is that, if water temperatures stay uniformly high, it stresses the fish and increases their metabolism, and causes them to not be able to settle down," Hebein said.
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Also of concern is the amount of oxygen in the water, which can be depleted by plant growth and algae brought on by the warmer water temperatures.
"We do have to be cautious if we want the fish to survive into the winter and be there again next year for fishing," Hebein said. "We also want to be sensitive to the impact fishing has on the local economy."
Typically, the CPW will first ask for voluntary restrictions, encouraging anglers to not fish along certain sections or to avoid fishing during the hottest part of the day in late afternoon and evening, he said.
"If the conditions are more serious, we will ask people to not fish at all, and in extreme cases we will do a closure," Hebein said.
The CPW asked for voluntary daytime fishing restrictions on local waterways last summer. The last full closure in the region was on the Yampa River in the extreme drought year of 2002, he said.
Recent afternoon and evening rains have helped to cool the rivers some, Hebein said.
"The monsoons are really saving us right now, both from wildfires and from high [water] temperatures," he said.
To help monitor water temperatures, the Roaring Fork Conservancy is also asking for anglers and citizen volunteers to help take water temperatures all up and down the waterway.
"The temperatures we are seeing now are not normal, even for this time of year, and are indicative of the drought we're experiencing," said Rick Lofaro, executive director for the Basalt-based river watchdog group.
"The reality is, even with the moisture we had in May, we were still only at 88 percent of total snowpack for the season," Lofaro said. "The runoff we did have disappeared quickly."
The combination of low streamflows, hot temperatures and a lack of rain in certain areas is exacerbating the problem, he said.
The Conservancy's "Hot Spots for Trout" program enlists volunteers to help record stream temperatures throughout the Roaring Fork watershed, including the Crystal River. Data can be uploaded to http://www.roaringfork.org/hotspotsfortrout.
Lofaro said the data will be shared with CPW officials and the White River National Forest to help the agencies gauge stream health.
"Our goal is to help everyone in the watershed to understand the issues around water temperatures and to modify their behavior," he said.
That includes not only anglers, but working with water users and irrigators that have ditch diversions on the Roaring Fork and Crystal rivers to limit water use, he said.