Drought causing more minerals to enter Sioux Falls drinking water source

A state water quality report says the part of the Big Sioux River that Sioux Falls uses for drinking water contains dissolved solids beyond the standards set by the Environmental Protection Agency. A city water official says the drought is causing the uptick in minerals, like salt.

The state Department of Agriculture and Natural Resources said in a statement that the minerals impact taste, color and odor, but don’t present a human health risk. The department is required to issue a water quality report every two years under the federal Clean Water Act. 

Ted Lewis, environmental engineer with the Sioux Falls Water Division, said the city is managing the problem with water treatment. 

“It’s not something that we’re overly concerned with,” Lewis said. “It’s just one of those parameters that we look at and we make sure we’re on top of it.

The point on the river where Sioux Falls gets some of its drinking water is just north of the airport. The public doesn’t drink that water directly — the water is treated first.

According to Lewis, the EPA advises water systems to keep dissolved solids between 300 and 500 milligrams per liter, and the water source in Sioux Falls has been reporting over 500 milligrams.

Lewis said the uptick in dissolved solids has to do with the drought.

“It’s just less water and sort of a concentrated amount of minerals in the water,” Lewis said. “And so that concentration just kind of creeps up a little bit when there isn’t that added rainfall to fill up the river and dilute things out.”

Lewis said the best way to mitigate the problem is by preventing soils from running off cropland and into rivers and streams. Planting grassy buffer strips along the river banks can help.

“The more grasslands that have buffer zones, the more plant life that can kind of take up those minerals, that’ll help slow the erosion or the seepage of the minerals into the water and at least keep it from getting exacerbated,” Lewis said.

And that is something the state is doing. The Department of Game, Fish & Parks is expanding a conservation program into the Big Sioux Watershed.

The department wants to enroll about 25,000 acres, starting in November. And about 5,000 of those 25,000 acres will target land along the Big Sioux riverbank.

The City of Sioux Falls was recognized by the state with a Secretary’s Award for Drinking Water Excellence this year for meeting all monitoring and reporting requirements, drinking water standards, and certification requirements for 10 or more consecutive years.

Other sources of drinking water in the report not meeting the EPA standards include a segment of the James River used by Huron, and portions of the Maple River and Elm River used by Aberdeen.

Firesteel Creek and Lake Mitchell are also listed, but they’re used only as emergency backups for the City of Mitchell. And Lake Waggoner and Durkee Lake, two more waterbodies listed in the report, are no longer being used as drinking water sources.