The State of Wyoming and the Bureau of Reclamation Upper Snake Field Office are working together to maintain flow releases from Jackson Lake Dam, to deal with a reservoir system imbalance.
Low snowpack above Jackson Lake and high storage contents in the upper Snake River reservoir system have led to the imbalance, which creates the potential for storage loss to the upper Snake River system.
Wyoming, in collaboration with Reclamation, has decided to make available its 2023 storage water to support releases from Jackson Lake Dam consistent with the Guidelines for Decision-Making in Operations of Wyoming’s Contracted Space in Palisades Reservoir, developed by Reclamation and Wyoming in 1996. Using the Operational Guidelines this year will satisfy Wyoming’s need to maintain 280 cfs releases from Jackson Lake Dam during this winter and spring and protect the 4.5-mile-long stretch of river below the dam, while also allowing Reclamation to maintain its legal and contractual commitments to Idaho irrigators.
The stretch of river below the dam, home to the world-famous Oxbow Bend, is critical habitat for Snake River cutthroat trout, shore birds, wildlife and the bluehead sucker — a species of greatest conservation need. Any reduction of water flow below 280 cfs in this area can harm the ecosystem and negatively affect outdoor recreation, tourism and angler opportunities.
According to current forecasts, there is a high likelihood of a spill past Milner Dam in southern Idaho occurring this season before Jackson Lake fills. To support the fishery below Jackson Lake Dam, Wyoming has decided to exercise its water right and will call for 230 cfs of the 280 cfs Jackson outflow to be released from Wyoming’s 2023 allocation. If conditions improve in the coming weeks, however, a cease water order from Wyoming would be submitted.
The original Jackson Lake Dam, completed in 1907, was a temporary rockfilled crib dam to store 200,000 acre-feet for the 28.5 MW Minidoka Project until the storage requirements could be determined. A concrete gravity structure with earth embankment wings was built at the site in 1911, increasing storage capacity to 380,000 acre-feet. In 1916, further construction raised the dam 17 feet to a structural height of 65.5 feet, with a total storage capacity of 847,000 acre-feet.
