Aquifer recharge possible, but costly

Lake Pend Oreille water can be diverted, study shows

Water from Lake Pend Oreille could be used to recharge the region’s drinking water supply, but it’s a costly option, a new study concludes.

The study looked at capturing spring flows from Lake Pend Oreille by drilling wells at the lake’s southern tip. The water would be pumped back into ground at other locations to recharge the Spokane Valley/Rathdrum Prairie Aquifer, which is the sole source of drinking water for nearly 600,000 of the region’s residents.

Recharging the aquifer would also bolster flows in the Spokane River, which reaches critically low levels by late summer. With as little as 100 cubic feet of water per second trickling over the rocks, some parts of the river are reduced to warm, stagnant pools.

But creating a system to capture lake water and inject it into the aquifer would cost about $90 million, the study said. Operating the system would cost another $12 million to $14 million annually.

The Washington Department of Ecology commissioned the $250,000 study, which was done by Washington State University researchers.

John Covert, a senior hydrologist for the Ecology Department, described the recharge study as a starting point for regional discussions about future water supplies.

“Knowing that it could be done doesn’t mean that it should or will be done,” he said.

But if future water conservation efforts fall short of meeting new demand, the study indicates that recharge is a technically feasible option for Idaho and Washington to consider, Ecology officials said.

Both population growth and climate change are expected to increase demands on the aquifer, which is connected to the Spokane River. Heavy pumping from the aquifer during the summer is already reducing the volume of water in the river, reducing flows for fish and recreation.

Lake Pend Oreille is Idaho’s largest lake, with an average of 18 million acre feet of water flowing through the system each year. The study looked at capturing a relatively small part of that – 50,000 acre feet over four months – for recharge, said Jani Gilbert, an Ecology spokeswoman.

A recharge effort wouldn’t affect lake levels during the summer, she said.

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