Large surface waves produced by powerboats are a mainstay for recreational watersports. A new study from the University of Minnesota shows that beneath the surface, factors such as propeller thrust and other types of waves can impact delicate lakebed ecosystems.
Researchers at the University's St. Anthony Falls Laboratory built on previous research to study the effects of powerboats on lake ecosystems over the 2022 and 2023 field seasons. The team placed acoustic-based sensors that measured pressure and velocities through the water column and at the lake bottom at two different locations and at two different depths. They also collected sediment samples and data on various water quality parameters.
The study was supported by a University crowdfunding campaign with over 200 donors. Additional funding was provided by the Environmental Natural Resources Trust Fund (ENRTF) as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).
The researchers tested seven recreational powerboats commonly used in Minnesota's lakes and rivers based on their two most-used settings. For non-wakeboats: displacement mode/leisure cruise and planing mode/cruising. For wakeboats: semi-displacement mode/surfing and cruising. The boats were driven directly over the measurement sensors five times for each operational condition.
Credit: St. Anthony Falls Laboratory, University of Minnesota.
The study, published in the University Digital Conservancy, found:
- All powerboats produce water currents and turbulence that can disturb the lakebed.
- More powerful turbulence from wakeboats can directly resuspend sediments in the water. This can indirectly lead to release of nutrients like phosphorus from sediment that can stimulate excessive algae growth, which adversely impacts lakes.
- All powerboats, when leisurely cruising or planing, should operate in 10 feet of water or greater to minimize impacts caused by motions generated by a boat's hull.
- During surfing, wakeboats should operate in depths of 20 feet or greater to minimize negative impacts on the lake environment.
"For all motorized boats, simply being careful about where you steer your boat and avoiding shallow spots can make a huge difference," said Jeff Marr, co-author on the study and associate director of engineering and facilities at the St. Anthony Falls Lab in the College of Science and Engineering. "Staying in deep water when you're out on the water - especially when wakeboarding or surfing - is an easy and effective way to enjoy and protect our waterways. Also, give space between your boat and other boaters and the shoreline."
Fieldwork for the final phase of the research will conclude in fall 2025. This project phase will examine how wind-driven waves differ from wake waves produced by recreational boats, including heir impacts on the lake environment.
Research partners from the St. Anthony Falls Lab include Andrew Riesgraf, William Herb, Matthew Lueker and Jessica Kozarek.
