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Irrigation utility could benefit lake water quality

Staff Writer | February 17, 2022 1:05 AM

MOSES LAKE — Using water from Moses Lake to irrigate parks, lawns and gardens across the city will likely benefit both the lake and underground water currently used for drinking, according to members of the Moses Lake Watershed Council.

Among those benefits, according to Grant County Conservation District Resource Conservationist Harold Crose, would be reducing the draw of water from aquifers underneath the city and reducing the amount of phosphorus in the lake.

“It appears to be a positive,” Crose said during an online meeting of the Moses Lake Watershed Council on Tuesday.

The council — which is comprised of representatives from the city of Moses Lake, the Grant County Conservation District, the Grant County Health District, the Moses Lake Irrigation and Rehabilitation District, the Washington State Department of Ecology, the U.S. Bureau of Reclamation and the Grant County Tourism Commission as well as several local citizens interested in improving the quality of the lake — was formed in 2018 in response to dangerous blooms of blue-green algae that prompted the health district to post warning signs telling people to avoid contact with lake water.

The city of Moses Lake and the MLIRD are currently considering an agreement to study the creation of an irrigation utility that could use up to 50,000 acre-feet per year of lake water that the MLIRD has rights to use.

Crose noted that there are a number of technical issues involved with the creation of such a utility, and it will be a long time before the city pumps any water out of the lake for lawns and gardens.

However, MLIRD board member Kaj Selmann said residents within the MLIRD already have a right to pump water out of the lake, and some are.

Selmann said irrigating lawns would take some of the excess phosphorus out of the lake and put it to use as a fertilizer, and that would be helpful in reducing the amount of the nutrient in the lake.

High phosphorus levels in both the lake water and the sediments at the bottom of the shallow lake are at least partly to blame for spurring the blooms of blue-green algae in hot summer weather. The algae itself is not dangerous, but when certain types of blue-green algae die, the individual cells can release toxins that are dangerous to fish, animals and people.

Crose said the Washington State Department of Ecology has set the maximum level for phosphorus in water at 30 parts per billion, though both Crose and Eugene Welch, an environmental engineer who has been studying Moses Lake for more than 50 years, said a level closer to 20 ppb is achievable.

According to a study published by Welch in April 2019 and available on the MLIRD website, phosphorus levels reached an average of around 37 ppb in the southern portion of Moses Lake in the summers of 2017 and 2018, while phosphorus in the northern part of the lake reached 63 ppb in 2017 and 91 in 2018.

Selmann said because there is no central metering system to measure how much lake water property owners in the MLIRD are drawing out, it’s impossible to know just how much of the 50,000 acre-feet the MLIRD has rights to are used. District residents who live near the lake and who pay the MLIRD assessment can draw water from the lake themselves.

“We have to do the work to get that answer,” Selmann said.

The Bureau of Reclamation uses Moses Lake to send Columbia River water to irrigators in the southern portion of the Columbia Basin Project.

Welch said that the roughly 200,000 acre-feet the Bureau of Reclamation has said it plans to run through Moses Lake this year should be enough to help keep the algae at bay.

“Over 200,000 acre-feet is the breakpoint for good water quality,” he said.

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