The Bureau of Reclamation and the Idaho Department of Water Resources are working on a project that will add more storage to the Boise River Basin by adding 29,000 acre feet of water to Anderson Ranch Reservoir, a seven percent increase.
"An acre foot of water would cover one football field about a foot deep, so picture 29,000 football fields that are one foot deep," said Chris Keith, the project manager with the Bureau of Reclamation. "If you can imagine one football field with all of that water, it would be four miles deep."
WATCH|Check out the video to see more of the dam and the reservoir as it's 88 percent full
We have done several stories on the Governor declaring a drought and concerns for farmers and irrigators this water season after a low snowpack winter. This project would save more water during the high snowpack years to help during the dryer years.
"There is a lot of interest in developing storage because of its ability to improve flexibility and improved reliability of water supplies," said Cynthia Bridge Clark with the Idaho Department of Water Resources. "It’s difficult to find new storage sites these days.”
This project started back in 2016 when the board of IDWR commissioned a study for long-term water needs due to the growth of the Treasure Valley. Water from Anderson Ranch flows down the South Fork of the Boise River to Arrowrock Reservoir, which dumps into Lucky Peak Reservoir and into the Boise River that runs through town.
The study found that with expected growth, by 2065 the Treasure Valley would need an additional 158,000 acre-feet of water to meet the demand for domestic, commercial, municipal, and industrial water.
In the last decade, we have seen significant growth in the Treasure Valley, not only with an increase in people, but also with large industries like Micron's expansion and new data centers that need water.
"We are seeing that growth play out and a project like this that will provide an additional 29,000 acre feet," said Bridge Clark. "It is just a part of the puzzle that will be a part of bridging that gap because it provides water supply that can be delivered where you need it and when you need it."
In 2018, Congress funded the Boise River Feasibility Study to find out if this project was possible. The Bureau of Reclamation just wrapped up the design phase after four years. A record of decision on the final environmental impact statement is expected by the end of the year and the next step is contracting the construction work in 2027.
The work includes replacing the spillway, performing crest modifications and addressing 18 different sites along the reservoir that will be effected from the water rising six feet. Some of those include recreation sites, roads, bridges, an airstrip and a fish ladder.
"Our total project cost is estimated right now at $149 million to get all that work done," said Keith. "That is from when we started looking at design and looking forward to what we project will be the year end of construction."
The state of Idaho will cover 88 percent of the cost using funds from general appropriations and from some of the American Rescue Plan Act COVID relief fund from President Biden. However, the state also gets 90 percent of the water while the Bureau of Reclamation will claim ten percent for federal benefits including fish, wildlife and environmental uses.
The Idaho Department of Water Resources is currently working on allocating the water rights, and they should have until 2032 to do so, as that is when a tentative date has been set for the project to be finished.
"There’s more interest than 29,000 acre feet, so the water board is working closely with the public to get a better sense of the level of interest and how to anticipate what those future needs are," said Bridge Clark.
