Fryingpan study: Winter flows linked to bug numbers

A study under way for a local nonprofit group shows a somewhat subtle way that drought or increased diversions from the Fryingpan River drainage could harm the quality of trout fishing and, therefore, the economy of Basalt.Initial results of a study performed for the Roaring Fork Conservancy indicate that low water releases during the three coldest winter months has a detrimental effect on the fishery of the Fryingpan.Miller Ecological Consultants Inc. of Fort Collins has tracked water releases and water and air temperatures over the last few winters, as well as counted the number and size of insects and examined their habitat in the spring to gauge the condition of the fishery.When the flow in the Fryingpan River drops below 60 cubic feet per second during the months of December, January and February, it’s easier for anchor ice to build in the river, according to William Miller, the principal owner of the consulting company.Anchor ice builds up from the bed of the river on cold nights. It breaks free when daytime temperatures climb. That ice scours the riverbed and decimates some of the macroinvertabrates that are the primary food source for trout.The lowest flows ever recorded were during the winter of 2002-03 because the U.S. Bureau of Reclamation was forced to reduce water releases. The reservoir level was low due to the drought that summer. When it became obvious that the snowpack would be below average that winter, the bureau had to reduce releases to let the water level rise in the reservoir.The flow in the Fryingpan hovered around 40 cfs most of the winter.Miller said his firm saw a substantial buildup of anchor ice that winter. Dave Rees, an entomologist with Miller’s firm, said overall numbers of macroinvertabrates remained high that spring. However, the biomass or combined weight of those insects was down. He said large bugs, such as stoneflies, were wiped out by the anchor ice.Flows remained higher the following winter and both the numbers and biomass of macroinvertabrates were high, according to Rees.Overall, he said, the Fryingpan River shows a healthy bug population. “When you compare them to other streams they are good,” Rees said.But he noted there needs to be a healthy supply because of the high demand by such a healthy trout population.Miller Ecological Consultants concentrated its study below the dam and at the confluence of the river and Taylor Creek.Jeanne Beaudry, director of the Roaring Fork Conservancy, said the consultant’s study, which is ongoing, is important to establish how flows affect the environment and economy. She noted that the Bureau of Reclamation has a stated goal of keeping flows above 40 cfs during winters, but no legal requirement.An ongoing drought could force the bureau to drop water releases from Ruedi which produce flows on the Fryingpan below 60 cfs and theoretically even lower than 40 cfs.In addition, increased diversions of water by Front Range cities from the upper Fryingpan drainage could reduce flows on the lower river. More diversion would mean less water flowing into the reservoir and, thus, potentially lower releases.Miller’s study will continue for years to establish trends.Scott Condon’s e-mail address is scondon@aspentimes.com