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Big ambitions to put water back underground

Tom Banse/Earthfix

Across the inland West, groundwater reserves are being depleted. Nature can’t replenish the aquifers as quickly as they’re being drawn down for irrigation, industry and drinking water.

But what if, through human ingenuity, we could put large volumes of water back underground at relatively low cost? Irrigators and the state of Idaho are making the most ambitious effort yet to do so in the Northwest.

Irrigation season has not yet arrived. The potato, sugar beet and barley fields of southern Idaho haven’t sprouted. Yet the Milner-Gooding irrigation canal was brimming with water on a recent visit to the site. It was nearly all spilling out of a gate and flume into a low spot in the desert north of Eden, Idaho.

The water had been traveling from the Snake River for about a day or slightly longer, said Brian Olmstead, who manages the Twin Falls Canal Company, an irrigation water provider in the area.

“It goes out into this recharge lake and then filters down through the lava rock, which is just what nature would do,” Olmstead said. “When this area is covered with snow and it all melts, it all goes down into the aquifer.”

The object is to stabilize the water supply under Idaho’s most productive farming region. The aquifer stretches thousands of square miles from the Teton foothills past Idaho Falls, Pocatello and Twin Falls to about Glenns Ferry.

“The Eastern Snake Plain Aquifer is also the sole source drinking water aquifer for at least a couple hundred thousand people, maybe more than that,” Olmstead said. “So having that aquifer going down was bad for everybody — everybody in the state, really.”

This infiltration basin is the biggest aquifer replenishment project among many planned in southern Idaho. The state also is paying irrigation companies to run water down unlined canals and ditches that would normally be dry during farming’s offseason. That’s another low-tech, fairly cheap way to let the water just seep and infiltrate down.

The state of Idaho and private partners have set a goal to triple the current amount of artificial groundwater recharge. The plan also would curtail water use by some farmers to take pressure off the aquifer.

One of the challenges of putting water back underground is preventing the introduction of impurities, Olmstead said. “Lava rock is a real good filter. There are least three monitoring wells around this site that monitor the groundwater to make sure there is no contamination.”

Idaho’s governor and legislature have committed $16 million for new infrastructure and planning for water sustainability statewide, much of which will flow to the Eastern Snake Plain Aquifer.

Northwest states have some advantages over other places coping with dwindling groundwater, said Scott Bedke, speaker of the Idaho House.

“We’re not like some of these other states, including California, Nebraska and Kansas, because we have ample water that, on average, leaves the state each and every year.”

Specifically, surplus river water in late fall, winter and spring that flows into Washington.

“If that were put into the aquifer and not allowed to leave the state, we could fix this problem,” Bedke said. “And that’s our intention.”

In southern and eastern Idaho, about 20 projects are in design, construction or under evaluation to replenish the subterranean aquifer.

Water basin efforts span multiple states

Other basins around the Northwest are ramping up too, for example, in the Walla Walla River valley on both sides of the Oregon-Washington border.

Steven Patten, who leads the aquifer recharge program at the Walla Walla Basin Watershed Council in Milton-Freewater, Oregon, said the goal in his area is to revive springs and improve stream flows for endangered fish.

“It’s different than a lot of aquifer recharge programs in that we’re putting (the water) into the system for the regional benefit, for environmental flows and for ecological improvement,” Patten said.

The techniques involved include diverting high flows in winter and spring from the Walla Walla River into manmade ponds where the water can soak into the ground. The project also has buried a series of perforated pipes five or six feet underground to create what it calls “infiltration galleries.”

Patten said the Walla Walla Basin Watershed Council is currently operating five infiltration sites on the Oregon side of the state line and four on the Washington side that together recharge about 7,500 acre-feet of water per year.

“We’re hoping to almost double that to about 14,000 acre-feet per year,” by opening more sites over the next two years, Patten said. “Our long-term goal is to eventually get to about 25,000 acre-feet per year.”

He said the long-term number would stabilize the entire Walla Walla aquifer, and then allow it to begin to recover.

For comparison, the Idaho Water Resource Board expects to recharge about 70,000 to 80,000 acre-feet in the Eastern Snake Plain Aquifer this winter and spring. The Water Board and state legislature have set an ultimate goal to return 250,000 acre-feet underground each year, which should ultimately stabilize the big southern Idaho aquifer.

One acre-foot is enough water to cover a football field one foot deep.

Imagine flooding the home fields of the Oregon Ducks, Washington Huskies and Boise State Broncos up to the press box level, essentially to the top of the stands. You would have to flood all three stadiums more than 550 times to equal the amount of water Idaho wants to put back into the Eastern Snake Plain Aquifer each year.

The assistant director of the Idaho Department of Water Resources told lawmakers this winter that his agency expects to replicate what it learns in southern Idaho to rebuild other declining aquifers such as the groundwater used in the Mountain Home, the Treasure Valley and Palouse areas.

In the Walla Walla basin, a wide range of funders are supporting aquifer recharge, including the Oregon Watershed Enhancement Board, Bonneville Power Administration, Washington Department of Ecology and local irrigation districts.

Aquifer recharge is not in itself new. What is new are the ambitions to greatly scale up the volumes of water involved in selected Northwest basins. The Walla Walla aquifer recharge program started in 2004 with one infiltration basin.

Near Hermiston, Oregon, the County Line Water Improvement District has used seasonal high flows from the Umatilla River for groundwater recharge since the 1970s. It diverts river water into an unlined canal, which allows the water to seep into a shallow aquifer from which it can later be pumped for irrigation.

According to the Oregon Water Resources Department, the County Line district recharges an average of 6,000 to 7,000 acre-feet per year.

Another technique to replenish groundwater that has found less favor in the Northwest is to use injection wells. This costs more per unit of water pushed underground and often requires the water to be treated to drinking water standard before it is directly injected into the aquifer.

EarthFix is a public media partnership of Oregon Public Broadcasting, Idaho Public Television, KCTS9 Seattle, KUOW Puget Sound Public Radio, Northwest Public Radio and Television, Jefferson Public Radio, KLCC and the Corporation for Public Broadcasting. EarthFix also is an Innovation Trail partner.