Five Years After Water Rights Agreement, Idaho’s Largest Aquifer Is Improving

By Rachel Cohen, Boise State Public Radio News

For decades, Idaho cities and farms have relied on the Eastern Snake Plain Aquifer. In the early 2000s, years of drought forced competing water users to come together. Five years into the compromise, officials say water levels are improving and that the system could provide some lessons for the West on managing declining aquifers.

Underneath southern Idaho, stretching into eastern Idaho, lies a body of water the size of Lake Erie. Brian Patton, the Executive Officer of the Idaho Water Resource Board, calls it a “world-class aquifer.” 

It supplies drinking water to about 300,000 people and irrigation water to more than 2 million agricultural acres, which, according to the water resource board, account for 20 to 30% of Idaho’s economic output.


For 50 years, water in the Eastern Snake Plain Aquifer declined, parallel to groundwater sources across the West, but before that, farmers were unknowingly filling the underground basin.

In the early 1900s, canal companies built the infrastructure that stretched the Snake River to dry desert land. 

“Moving water from the Snake River out across the Snake River plain, we, overtime, added a lot of water to storage in the aquifer,” Patton said. 

As farmers flooded fields to irrigate crops, some of it seeped through the basalt, filling the natural reservoir beneath the surface. Canals that snaked the valley leaked some water into the ground, too. By 1950, the aquifer had almost 20 times the amount of water as it did in 1912. But then things began to change.

“Roughly about that time is when we started seeing large scale groundwater development,” Patton said. 

Cities from Twin Falls to Rexburg grew substantially, and big industries like food processors set up shop. All of this required a lot of water. So people began pumping from the ground. At the same time, farmers switched from flooding fields to irrigate crops to more precise sprinkler methods, so there was less excess water seeping through the soil.

Water levels in the aquifer began falling as steadily as they’d been increasing for the first half of the 20th century. Then, after cycles of droughts in the 1970s and 1980s, came a few excessively dry years in the early 2000s, meaning not everyone could get the water they’d be allocated.


Under the rules of “prior appropriation,” water in Idaho — and the West — is allocated to the first person who uses it in a “beneficial” way. The policy is otherwise known as “first in time is first in right,” because the date of the water right determines who gets water when there’s not enough for everyone.

In Idaho, systems to bring people water from the Snake River or natural springs were established earlier than groundwater pumping began, so surface water users are senior to groundwater users, and thereby are entitled to get their full share first.

After 1950, when Eastern Snake Plain aquifer levels were declining, the state continued to dole out water rights. But, during extremely dry years, springs like American Falls and Thousand Springs ran low. 

“Businesses and industries and canals that relied on those spring flows, start getting significantly less water than they were used to,” Patton said. 

Companies, including Magic Valley canal operations and fish farms, started getting upset and filed water delivery calls against groundwater users with more junior water rights. 

“Basically what that says,” Patton said, “is ‘Hey, I’m not getting my full water supply. I think there are junior water right holders pumping that water out of the aquifer before it shows up in the spring that delivers water to me.’”

Water calls turned into lawsuits — a few went to Idaho’s supreme court — and groundwater users spent a lot of money trying to defend themselves and meet their legal obligations to the senior surface water users. All the while, the aquifer was going down.

“And in 2015, as the irrigation season approached, we’d had a really dry winter,” said T.J. Budge, an attorney at Racine Olsen Law Firm in Pocatello who has represented the Idaho Ground Water Association. 

“The amount of water that was projected to flow into the Snake River, from snowpack and reservoirs and from the aquifer, was expected to be down that year,” he said.

That meant there was a real possibility that water could be shut off for groundwater users for the first time.

It was a wake-up call that the state needed a long-term solution.

Standing beside the Milner-Gooding canal near Eden in March, Brian Olmstead watched water rushing from the irrigation channel to flood an adjacent field.

The canal that usually transports water to desert farmland in the summer, but in the offseason it’s used to direct surface water to the Eastern Snake Plain Aquifer.

“We’re trying to rebuild the aquifer after 60 years of taking more out than mother nature’s putting back in,” Olmstead, the manager of the Twin Falls Canal Company, said.

The surface water seeps through the cracks in the lava rocks until it hits the aquifer — probably 200 to 250 below, Olmstead said.

This contraption — labeled Mile Post 31 — is an artificial recharge site, where water is directed from the Snake River to the aquifer to help it refill after years of decline. 

“You’ve got two choices,” Olmstead said. “You either take out farmland, or you put more water back in the aquifer, so you can maintain the farmland.”

Drying up farmland seemed like a real possibility for groundwater users like Dean Stevenson as the 2015 growing season approached. He grows sugar beets and barley near Rupert and pumps water from wells on his property, and remembered getting a call five years ago from the Idaho Department of Water Resources.

“Hey, you’re gonna have a pretty big obligation this year and you may not be able to meet it,” he recalled they told him. 

Stevenson, who has some of the older water rights among groundwater users, remembers thinking he could not get all the water he needed to irrigate his crops, meaning farmers like him, producing some of Idaho’s most valuable agricultural goods, may have to dry up fields. 

“I mean you were living by the director’s next order, and you were living and dying by whether it rained or snowed and what the water supply was going to be,” Stevenson said.

In 2015, it was becoming clear that the tug of war over this resource wasn’t just going to end.

Speaker of the House Scott Bedke and Idaho State Senator Steve Bair stepped in to negotiate a settlement between the surface water and groundwater folks. In a firehouse in Paul, Idaho, they went back and forth — groundwater users on one side of the building, surface water users on the other, and Bedke and Bair in the middle. After months, the two sides came up with an agreement. 

To stabilize declining aquifer levels, groundwater irrigators agreed to reduce their pumping collectively by 240,000 acre feet a year. 

As a result, some groundwater users have had to adjust — plant different crops that require less water, get innovative with irrigation or even forgo planting on some fields. And while that costs them money, Stevenson said, to him, the compromise has given groundwater users more stability. 

Another important component of the plan to rebuild the aquifer was the state agreed to recharge an average of 250,000 acre feet a year into the aquifer — more in wet years and less in dry years — at sites like the one Olmstead visited in March.

Five seasons later, water levels in the Eastern Snake Plain Aquifer have started to come back up. Partly because they’ve been good precipitation years, Patton of the water resource board said, and partly because the state and other partners have rallied around aquifer recharge, bringing the money to the table to make it happen. 

“This is pretty unique and pretty historic and is really kind of at the forefront of integrated groundwater and surface water management movement in the West,” Patton said. 

It’s something other states could learn from, too, said Michael Kiparsky, who runs the Wheeler Water Institute at the Center for Law, Energy & the Environment at the UC Berkeley School of Law. Kiparsky is looking at the Eastern Snake Plain Aquifer as an example of how Western states can manage groundwater. 

“They have managed to reconcile an incentive for recharge at very large scale,” he said.

Part of what sets Idaho apart, Kiparsky said, is the state has recognized in law for more than 20 years the hydraulic connection between groundwater and surface water, or the Eastern Snake Plain Aquifer and the Snake River. 

“That is the lynchpin for why [the Eastern Snake Plain Aquifer] is an interesting case, and why it’s a more holistic water management solution than you see in other places in the West,” Kiparsky said.

Some other states, like California, that are desperately trying to figure out how to reverse aquifer depletion are behind. Until a 2014 bill, California operated as if they were two separate water sources — what Kiparsky calls a “legal fiction.” 

Managing surface and groundwater together means that surface water users can argue that groundwater users pumping too much water is causing their water shortages. But this system also means the two groups have to work together to manage the aquifer — because they’re both affected by its decline.

“I’m a surface water canal, but my water comes out of the ground — a lot of it in the American Falls area,” Olmstead said.

“It might be years later, but it all comes back to the Snake River. It doesn’t go to China, it doesn’t go to Missouri, it doesn’t go to California, it comes back to the Snake River,” he said.

This conjunctive management has water users on both sides thinking that this agreement is sustainable. Patton of the water resource board said it is, so long as recharge efforts keep up and the funding behind them stays in place. 

But he also knows the agreement hasn’t been tested by a multi-year drought, something that’ll likely be more common with climate change, forcing the state to continue to adjust its methods. 

Find reporter Rachel Cohen on Twitter @racheld_cohen 

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