Watering Idaho: One Chart Explains The Last 100 Years Of The Eastern Snake Plain Aquifer

Sep 19, 2016

It’s no secret that Eastern Idaho has a water problem. There is too much demand and too little water in the Eastern Snake Plain Aquifer to go around. But how did we get to this point? That’s what this chart is all about.

About 100 years ago, there was roughly 4,000 cubic feet per second of water coming out of the aquifer at Thousand Springs. It’s important to note that’s not how much water was in the aquifer, just how much was flowing out.

Back then, the aquifer got a lot of its water naturally from rivers and tributaries. Then, farmers started cultivating fields on the Snake River Plain. Farmers watered those crops with flood irrigation. And as that water flooded into the fields and furrows, a lot of it sank into the ground, into the aquifer. Slowly, over 40 years, the aquifer took in more water. A lot more water.

From 1912 through 1952 the aquifer ballooned, adding 17,000,000 acre feet of water. That's the left side of the bar chart. More water in meant more water out and farms continued to grow. So did cities. Everybody needed more water and asked for more water rights. Idaho complied, granting those rights.

“We improved the storage for a period of about 40, 50 years and everyone got used to that,” says Sean Vincent, Hydrology Section Manager at the Idaho Department of Water Resources.

But after 1952, things began to change.

“Beginning in 1952, for a variety of reasons,” says Brian Patton, “the aquifer storage started going down.” Patton is the Bureau Chief at Idaho Department of Water Resources. That's the right side of the bar chart.

Water flows out of the Snake River Plain Aquifer into the Snake River. In the early 1950s, the amount of water coming out of the aquifer hit its peak.
Credit Samantha Wright / Boise State Public Radio

“Groundwater pumping going on at that time had an effect. Large scale groundwater pumping started in the late 1940s,” says Patton.

Then there was electricity and drilling, which allowed people to put in wells and irrigate fields that they couldn’t reach with surface water.

So there was more demand for the water. And there were more droughts, putting a strain on the system. But there was another problem.

“The surface water canals got more efficient at delivering their water,” says Patton. That’s the bigger issue in his mind.

On the chart you can see drought years and good water years over the last 60 years. But after every drought cycle, the good water years were just a little less good than the last time. That meant farmers had to adapt to get water to their fields. They got more and more efficient at delivering water each time.

“During those drought cycles, those efficiency improvements by the surface water canals by the irrigation districts … they accelerate those improvements,” says Patton.

Farmers lined the canals to keep water from seeping into the ground. They put in automation and regulating ponds. They went from flood and furrow irrigation to sprinklers and center pivots to maximize their water use.

“They do other things to optimize the efficiency of their delivery and lose less of it [the water],” says Patton.

“The people who were flood irrigating with surface water, put in sprinklers. They’re more efficient and you get less incidental recharge from a sprinkler system than you do from flood irrigation,” says Dr. Allan Wylie, Technical Hydrologist at IDWR.

As farmers got more efficient, the aquifer got less recharge. “Less water is getting back into the aquifer as a by-product of irrigation operations,” says Patton.

“It’s that increasing efficiency that is sort of irreversible. We never go back to less efficient irrigation practices,” says Vincent.

In effect, the farmers were irrigating smarter, as less water became available.

“Every time that they figure out ways to get the water that the crop needs, and minimize the waste. That’s their job, that’s not the wrong thing to do. But, it results in less water in the aquifer,” says Wylie.

Since 1952, the aquifer has been losing 215,000 acre feet of water each year. After 60 years of less water going into the aquifer, it has shrunk dramatically.

“Today, we’re back at about the same level of aquifer storage that we were about a hundred years ago,” says Patton.

So there has been a steady downward decline in the aquifer for the last 60 years.

“We jacked it up on steroids for a couple of decades. Now we’re paying for it,” says Wylie.

Less water is coming out of the aquifer at Thousand Springs now than in 1952. Some of that water is captured as it comes out by fish farms and power generators.
Credit Samantha Wright / Boise State Public Radio

Why do we care? Well, there’s less water to go around for farms pumping from the aquifer. And as aquifer storage drops, so does the amount of water coming out of Thousand Springs, where the aquifer dumps its water into the Snake River. That has a big impact on all the water users, especially fish farms and power generators using the water pouring out of Thousand Springs. And it has ramifications downstream on the Snake River.

As senior water rights holders saw their water flow decrease, they objected and made water “calls” to the Idaho Department of Water Resources. Now the holders of older water rights were in direct competition with those with younger rights. Too much demand, not enough water. Farmers and other users today have 13,000,000 acre feet less water at their fingertips than in 1952. Now entities like the IDWR, groundwater pumpers and other water users are working on finding a solution. But that won’t be easy.

“It’s a lot easier to turn around a bicycle than an aircraft carrier. And this is going to be more like turning around an aircraft carrier. It’s got a lot of momentum in the wrong direction that has to be overcome,” says Wylie.

There’s been a moratorium on the issuance of new water rights across the eastern Snake River Plain since 1992. But that’s not enough.

Over the last year some of the users started implementing a settlement agreement. The groundwater users on the Snake River Plain collectively agreed to reduce their groundwater use by 240,000 acre feet a year.  That will help stop the decline of the aquifer. The state is creating a recharge program to add 250,000 acre feet of water a year into the aquifer. That will help build the aquifer back up. But the agreement doesn’t cover everyone and it’s just the start of trying to meet all the demand that has grown on the Snake River Plain.

Will the aquifer ever swell back up to the size it was in 1952? Not likely, say the experts. The hope in the short term is to get enough water to those who have a water right and want to use it.

Find Samantha Wright on Twitter @samwrightradio

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