Scenic boat tours on Jackson Lake in Grand Teton National Park shut down about two months early this year because water levels are dropping faster than normal to meet the irrigation demands of farms along the Snake River in southern Idaho.
The lake’s irrigation reserve was 60% full Monday, compared to a normal level of 63% this time of year, Brian Stevens, water operations civil engineer with the Bureau of Reclamation, told Cowboy State Daily.
Water levels have dropped to the point where large tour boats aren’t able to get out of Colter Bay Marina and onto the main body of the lake, Grand Teton spokeswoman Emily Davis told Cowboy State Daily.
That happens every year, but it came unusually early this summer, said Sarah Howe, director of sales and marketing for Grand Teton Lodge Co., which runs the boat tours.
“At the Colter Bay Village Marina, we shut down our scenic and meal cruise boat operations during the week of July 12 due to lowering lake levels,” she stated in a text to Cowboy State Daily. “Typically, we shut down those operations sometime in early to mid-September.”
Hybrid Lake/Reservoir
As to whether Jackson Lake is a natural lake, or a reservoir, it’s actually both.
The natural lake, fed by the Snake River, was already one of the largest in the West when it was enlarged by a dam in 1911. That dam was enlarged in 1916 and rebuilt in 1989.
In its current state as a hybrid lake/reservoir, Jackson Lake is 438 feet deep at its deepest point.
The top 33 feet of the lake is spoken for as irrigation water for Idaho farmers, Stevens said.
From the Bureau of Reclamation’s standpoint, saying the lake is “63% full” means 63% of that top layer earmarked for irrigation, not 63% of the lake in total, he said.
“There’s still about a 2 million-acre-foot natural lake below” (the irrigation water) that remains untouchable, Stevens said.
Jackson Lake sits at the top of a massive irrigation system along the Snake River that includes Palisades Reservoir, American Falls Reservoir and Lake Walcott in Idaho.
That’s the main source of crop irrigation for potatoes, sugar beets and alfalfa.
And there has also been a growing demand for silage corn to feed cows on massive dairy farms in southern Idaho, Stevens said.
Jackson Lake’s water level is dropping unusually fast this year because in-flows were lower than normal in the wake of a dry winter, he said.
Meanwhile, downstream irrigation demands remain steady.
“Reservoir levels are low throughout the system,” Stevens said.
How Low Will It Go?
Drawdown on Jackson Lake usually goes until late August or mid-September, Stevens said.
It’s not clear how low the lake will get this year, he said.
The lowest the lake has been in recent memory was down to 25% of the irrigation reserves in 1988, he said. And on one occasion in the early 20th century, it dropped to 7%.
In addition to Colter Bay, boat ramps are at Signal Mountain Lodge and Leeks Marina. A “primitive” boat launch site is at Spalding Bay.
Leeks Marina usually retains enough water to launch motorized boats later than the other boat ramp locations, Stevens said.
People using canoes, kayaks and other small craft will “still have spots where they can get into the water” regardless of how far the lake drops, he said.
Davis agreed the outlook for smaller motorboats and human-powered watercraft is good for a while yet.
“Leeks Marina would probably be the last one to shut down,” she said.
She noted there have been other years when the lake was unusually low, most recently in 2021.
Lost Revenue
Grand Teton Lodge Co. will likely feel the early shutdown of boat tours, Howe said.
“While there is a loss of revenue from those specific operations (boat tours), we still provide a number of other services both at the marina and also on the Snake River, our corrals, and our scenic bus tours to provide alternative experiences to our day use and overnight guests,” she stated in an email.
Mark Heinz can be reached at mark@cowboystatedaily.com.
