Rebuilding the Teton Dam is back on the table.
The Henry's Fork Basin Study is moving forward with researching several water storage and other alternatives that could be used to address the water supply needs of eastern Idaho and the eastern Snake Plain.
Bob Schattin, activity manager for the Bureau of Reclamation, leading the study, told a standing-room-only crowd in Driggs April 20 that the idea of a new Teton Dam "came out very low in our ranking system. It's very unlikely."But "a rebuild of Teton Dam is currently checked as a carry-forward alternative," said Sarah Rupp, streamflow restoration director for Friends of the Teton River, with costs to be determined and brought up to date from a 1991 analysis of this site.
Although the concept will be carried forward, "basically the 1991 study went further than any of the anticipated reconnaissance alternatives, so we will restate the conclusions of the 1991 study and no further analysis will be done," Schattin said.
The BOR is working with the Idaho Department of Water Resources on the $800,000 study that is researching how to meet the water needs of the region for the next 40 years. The eastern Snake Plain aquifer is reported to be in a deficit of 600,000 acre-feet of water, Schattin said.
At the Driggs meeting on the study, the Teton Dam was considered "a non-starter due to economic reasons," said Rupp. But "it's an interesting proposal. It's still a commissioned dam site and it's the site with the largest storage capacity at 200,000 acre feet. It's the real game-changer for water delivery in the bunch."
Palisades Dam was the last local project of this type. A project of that size lends itself to holding up a lot of water that can be delivered at different times of the year, Rupp said.
Large storage facilities can really impact the timing, delivery and reliability that people can count on, said Rupp. Some of the smaller storage alternatives don't hold as much water up high and may not be as significant in reliability and deliverability of downstream water.
The reconnaissance stage of the study will further examine the most viable storage alternatives as defined by the study group. Besides the Teton, other options under consideration include construction of dams on the following tributaries:
Upper Badger Creek - 50,000 acre-foot storage facility
A dam here could adversely affect strong populations of Yellowstone cutthroat trout, Rupp said. The study suggests those effects could be mitigated by a man-powered fish segregator.
Spring Creek, a tributary to Canyon Creek - 30,000 acre foot storage facility
Spring Creek is a tributary of Canyon Creek, which flows into the Teton River. There's a strong population of Yellowstone cutthroat trout in Canyon Creek, and agencies are looking for work on that creek to preserve those populations, Rupp said.
Moose Creek, a tributary to the Henry's Fork River - 60,000 acre foot storage facility
This surface-water storage alternative is on Moose Creek north and east of Island Park Reservoir. That would be additional storage on the Henry's Fork rather than the Teton, said Rupp. The option could be combined with increasing capacity of the Cross Cut Canal to move more water from Island Park Reservoir to the Teton River.
The study group is also considering expansion of the Ashton Dam in combination with expanding the Cross Cut Canal.
An off-stream reservoir, dubbed Lane Lake, would be an off-site dam that could hold back about 70,000 acre feet of water filled primarily by Bitch Creek and Conant Creek water. The lake would sit northeast of the old Teton Dam site.
Being an off-stream site minimizes some environmental concerns, "but the largest concern is pulling water from Bitch Creek," she said.
"Our fisheries research indicates that really core, strong populations of Yellowstone cutthroat trout have been so productive in that area because the traditional hydrograph is largely intact."
Hydrographs show that the area has very high peaks of water during runoff, which is ideal for YCT production, said Rupp.
"Shaving off that real large peak opens the opportunity for non-native species such as rainbow trout to invade those streams," she said. That could dramatically impact YCT, she said.
"A lot of study is possible on Lane Lake including any possible configuration," said Schattin. "There are a number of potential sites, elevations, and configurations which could change the capacity a lot."
To contact Ken Levy email firstname.lastname@example.org.