POST FALLS — As boat traffic increases on the Spokane River, officials are beginning to study its impact.

Craig Cooper of the Idaho Department of Environmental Quality said they've seen a large increase in boat traffic and are receiving complaints about wake and surf boats affecting property and public safety.

"Given this growth and the historic impacts of metals on Lake Coeur d'Alene, we're concerned that we may be approaching levels that could be environmentally and ecologically damaging," Cooper said.

Frank Wilhelm, a University of Idaho professor who studies inland waters and ecological systems, has begun research to differentiate between natural and human-caused impacts.

"We've distinguished between waves caused by wind and waves caused by humans," Wilhelm said.

In 2023, his team started tracking how different types of boats affect the river environment. 

"The whole reason I got into this was that we had no numbers," Wilhelm said, emphasizing that comprehensive data will help inform better decisions.

Wilhelm is collaborating with Cooper and DEQ surface water manager Robert Steed to test metal toxicity and determine exposure risks as increased boat traffic resuspends metals in the water. His primary concerns include high levels of lead, cadmium, and arsenic.

During data collection on a busy day in 2024, Wilhelm's team counted 900 boats over 12 hours on the Spokane River. While more data is needed, preliminary results suggest water quality is generally better before a boat passes than afterward, regardless of wake type.

Wilhelm said that the river's confined space creates "a kind of bathtub effect" where secondary and reflective waves from opposite shores compound water quality impacts.

His research focuses on phosphorus, which nourishes aquatic life but can become harmful when excessive. A University of Idaho study is measuring water quality at various distances before and after different boat types pass through. This research will continue through summer 2025.

Wilhelm acknowledged the challenge of finding middle ground that preserves water quality while allowing recreational enjoyment.

"We have a great resource here, but if the resource goes away, everything it's connected to goes away as well," Wilhelm said.

He hopes the collected data will help stakeholders work together toward balanced solutions.

 "We're loving our lakes to death," Wilhelm said. "As humans, we do some crazy things and then we wonder why we have a problem."

    Spokane River Secchi data for summer 2024. The readings were taken at the west end of Greensferry Bay.