South Dakota environmental regulators are accepting public comments on a new set of draft pollution reduction targets for a 10-mile segment of the Big Sioux River in Brookings County.

The document from the Department of Agriculture and Natural Resources proposes “total maximum daily loads,” which are the levels of pollution a waterbody can suffer and still meet water quality standards. About 450 square miles of land form the watershed for the river segment from Volga to south of Brookings.

The river segment is too polluted to support some kinds of warmwater fish, according to the department. The problem is “total suspended solids,” including soil that washes into the river. Roughly 73% of that soil comes from farms. 

“The watershed is used extensively for agriculture, which comprised 88% of the land area in 2017,” the department’s report says. 

The report also notes that wetlands, forests and native grasslands have declined in the watershed.

Fish affected

Travis Entenman is the managing director of Friends of the Big Sioux River. He said suspended solids affect plant and fish life.

“Excessive sedimentation reduces oxygen levels and blocks sunlight that our underwater plants need,” he said. “If we had clearer water, more fish — outside of carp — would be able to thrive.”

University of South Dakota Sustainability and Environment Professor Mark Sweeney said research shows suspended solids in the Big Sioux have increased in the 2000s compared to the 1970s and ’80s. He said the problem is especially bad for filter-feeding fish.

“They basically choke on the sediment,” Sweeney said.

He added that other fish dependent on good visibility are also affected. 

The segment of the Big Sioux is one of many polluted waterways in South Dakota. A recent report showed about 80% of the rivers, streams and lakes tested in South Dakota are too polluted for at least one of their intended uses.

A goal, not a mandate

The department’s recommendations for the 10-mile Big Sioux segment say no water sample should have more than 158 milligrams of suspended particles per liter, and the average should stay below 90 milligrams over any 30 days.

The plan also includes recommendations: relocating livestock away from streams, protecting grasses along streams, conserving wetlands and sloughs, and promoting soil health practices that reduce sediment runoff. It also advises continued funding and marketing of existing financial incentives for those practices.

Existing incentives include a $3 million state program paying landowners to grow and maintain grass strips along the river and its tributaries. The state pays up to $575 per acre for cropland and up to $157 per acre for pastureland enrolled.

Incentives are the primary way the state attempts to achieve cleaner waterways. Jay Gilbertson, manager of the East Dakota Water Development District, based in Brookings, said the state does not mandate action by individual polluters.

“The department says, ‘We don’t want to make people do anything,’” he said. “Well, that’s the problem then.”

Entenman agreed, saying he welcomes the development of the total maximum daily loads and the report about where the pollution originates. But, he added, “We need to make sure there is follow-through and these issues are being remedied.”

Marisa Lubeck, a spokesperson with the U.S. Environmental Protection Agency’s Region 8 Office (which includes South Dakota), sent a statement explaining states and local governments are responsible for ensuring plans are followed. 

“The plan provides a foundation to support future implementation, which is led by state and local organizations rather than the federal government,” she said.  

Public comments on the draft document must be submitted by Sept. 28 and may be emailed to DANRmail@state.sd.us.