Swan River eyed for water storage
SUMMIT COUNTY – Water planners are giving new attention to a dust-covered plan to build a reservoir in the Swan River drainage north of Breckenridge.Renewed interest in the small reservoir comes as drought and growth are putting a focus on increasing water supplies across the state.”It’s got a lot of appeal to put real water, wet water in the upper end of the Blue and Snake rivers,” County Commissioner Tom Long said.”It might be a better deal than some of the other things we’ve been looking at,” he said, explaining that stored water in the Swan drainage could help ensure actual “flow water” is available for the many water right-holders.While all eyes lately have been on Wolcott as the site for a major new Western Slope reservoir, another group of water players is taking another look at the Swan River.For now, a group of stakeholders from both sides of the Continental Divide, including Summit County and the Colorado River District and Denver Water, are trying to forge an intergovernmental agreement that would set the groundwork for detailed studies of the site, said Eric Kuhn, executive director of the River District.Kuhn said the Swan River talks are at a very preliminary stage.
Depending on configuration, the potential is to store as much as 10,000 to 30,000 acre-feet of water in the Swan River drainage, Kuhn said. An acre-foot of water supplies the average household for a year.Another local water expert, Taylor Hawes of the Summit Water Quality and Quantity group, recently told Dillon Town Council members that discussions are focusing on a site near the confluence of the Swan’s North Fork, with a capacity between 9,100 and 11,000 acre-feet. The site was identified for potential storage as early as the 1970s in a study involving the Middle Park Water Conservancy District, Long said.Much more site-specific work, including seismic and drilling, needs to be done to determine if a reservoir could be built cost effectively, Kuhn said.For example, geologists must establish how deep the alluvial material is in the valley since the dam foundations must be anchored in solid rock. That’s one of the key factors to determining the cost of construction.One earlier study attached a $30 million price tag to such a project. Kuhn said one early goal is to update the research using today’s numbers.Summit County owns conditional water rights for the storage project, but Kuhn explained that, in general, those rights are junior to most rights in Dillon and Green Mountain reservoirs.
The Swan reservoir would be filled during peak spring runoff, capturing the conditionally owned water that for now runs down the Swan and Blue River, unused locally.The Blue River between the confluence of the Swan and Dillon Reservoir is a water “pinch point,” according to Kuhn, where competing water rights bump into each other.Upstream from the reservoir, the Blue provides important spawning habitat for brown trout, according to the Colorado Division of Wildlife. The reach is protected by a minimum instream flow held by the Colorado Water Conservation Board to protect the environment to a “reasonable” degree.In the drought summer of 2002, officials weren’t sure that flow could be maintained without cutting off other upstream users, including residents participating in a well-water augmentation plan. Winter snowmaking diversions and flows to and from the wastewater treatment plants in the area are also at issue in the complex picture.Proposed reservoirs farther downstream – Wolcott, for example – have the potential to result in greater Denver Water depletions to the Blue River and potential impacts to Dillon Reservoir levels. Any new water storage above Dillon Reservoir could be valuable.Kuhn said one of the biggest potential hurdles is the impact to a large wetlands complex associated with the North Fork of the Swan.
The larger looming question deals with the availability of water to fill the reservoir. In wet or normal years, based on historic patterns, it likely would fill. But if drier conditions prevail, even the peak runoff might not be adequate, Kuhn said.One of the intriguing aspects of the Swan reservoir site is the potential to move water into the Snake River drainage, via Soda Gulch, a drainage between Keystone and Summit Cove that Kuhn said is “overused.” Soda Gulch provides underground water for domestic use in Summit Cove and also helps supply a small reservoir at Keystone Ranch.”With the issue of metals in the Snake, it would be good if you could move water. You could improve habitat immensely,” Long said, explaining that the project could potentially boost Keystone’s snowmaking potential. A Swan River site could also help with snowmaking in Breckenridge, at least via exchange for upstream water, he added.Discussions on the Swan River site should be seen in the context of general, ongoing discussions of water supply here in the headwaters region of the Colorado River, Long said. Officials have also been talking about an enlargement of Old Dillon Reservoir, or even some way of tapping into Dillon Reservoir as a source for local use.
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