BREAKING ANCHOR (ICE)
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Pitkin County is part of a large coalition of local and statewide entities, working to reduce the formation of anchor ice on the lower Fryingpan River.
#BreakAnchorIce |
What is anchor ice?Anchor ice is submerged ice attached or anchored to the bottom of a stream or other body of water. It forms in a variety of ways. Locally, the common denominators are low stream flow and extremely low air temperatures. When air temps drop water temps to 31.3 degrees F, anchor ice begins to form on the rocks at the bottom. This occurs much more rapidly when streamflows are low, because there is less water, meaning it is easier for the air to cool the water. This is particularly true at riffles where the streambed is very close to the surface.
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Why is it a problem?Anchor ice damages, and reduces the availability of streambed habitat critical to the life cycle of macroinvertebrates. What is bad for macroinvertebrates is bad for fish, and so on down the food chain. In terms of ecological consequences, it can take years for the streambed to recover from major anchor ice events.
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What are we doing about it?
The flow of the lower Fryingpan, below Ruedi Dam, is historically managed in the neighborhood of 39 cfs during the coldest months of the year. At these flows, anchor ice formation is a common occurrence. A study conducted by the Roaring Fork Conservancy determined a flow of 70 cfs would create enough kinetic motion in the river and keep water temperatures high enough, to prevent the formation of anchor ice. As such, the anchor ice prevention program’s intention is to put more water down the Lower Fryingpan between December 16 and March 1st. Multiple local and statewide groups have teamed up to raise the funds needed to lease the water necessary to bridge the gap between the current minimum streamflow of ~39cfs, and the 70cfs target for river health.
The water is being leased from the Colorado River District who owns contract water in Ruedi Reservoir. The lease rate is $68.50 per acre foot. An estimated 3,500 acre feet of water per winter season will be necessary to optimize the flows.
Pitkin County, through the Healthy Rivers program, is a lead funder of the $280,000 program. Roughly half of that cost has been provided by the Colorado Water Conservation Board. Pitkin County Healthy Rivers is contributing $50,000, the Colorado Water Trust $30,000, and the Colorado River District (through their community funding partnership) $20,000. The Roaring Fork Conservancy, city of Aspen and, town of Basalt have each chipped in $10,000, with an additional $1,000 coming from the Roaring Fork Fishing Guide Alliance.
The Roaring Fork Conservancy is monitoring river flow levels, water temperature, air temperature, and anchor ice presence, from December through March. The data will be compared to previous years to both look for trends and build a long-term data set.
The water is being leased from the Colorado River District who owns contract water in Ruedi Reservoir. The lease rate is $68.50 per acre foot. An estimated 3,500 acre feet of water per winter season will be necessary to optimize the flows.
Pitkin County, through the Healthy Rivers program, is a lead funder of the $280,000 program. Roughly half of that cost has been provided by the Colorado Water Conservation Board. Pitkin County Healthy Rivers is contributing $50,000, the Colorado Water Trust $30,000, and the Colorado River District (through their community funding partnership) $20,000. The Roaring Fork Conservancy, city of Aspen and, town of Basalt have each chipped in $10,000, with an additional $1,000 coming from the Roaring Fork Fishing Guide Alliance.
The Roaring Fork Conservancy is monitoring river flow levels, water temperature, air temperature, and anchor ice presence, from December through March. The data will be compared to previous years to both look for trends and build a long-term data set.
