Evaluating effectiveness of flocculation and wave-reduction barriers for restoration of a turbid, terminal lake

Wetlands Ecology and Management
By:  and 

Links

Abstract

Malheur Lake is a freshwater, shallow lake that provides key habitat for birds along the Pacific Flyway in North America. The lake shifted to a turbid state in the 1990s with suspended-sediment concentrations sometimes exceeding 1000 mg/L and minimal light available in the water column for submerged aquatic vegetation. Resource managers intend to enhance bird habitat quality by restoring the lake to a clear, vegetated state. Ten mesocosms were installed to experimentally test the effects of wave-reduction barriers and flocculation (aluminum sulfate followed by lanthanum-modified bentonite clay) on dependent variables including turbidity, suspended-sediment concentrations, nutrient concentrations, and photosynthetically active radiation. Flocculation additions temporarily decreased turbidity by ≥ 90% and significantly increased photosynthetically active radiation by > 400% through the water column. Orthophosphate concentrations significantly decreased following the first flocculation addition. The clay did not cap the flocculated material, and turbidity increased within a few days from wind-wave action. Wind directions in the middle of the lake were variable, minimizing the effect of wave-reduction barriers on dependent variables. This study showed that the light required for submerged aquatic vegetation can be temporarily attained at the lakebed using flocculation. Future experiments could attempt to prolong the duration of low turbidity by effectively capping the flocculated material. The findings demonstrate the complexity of disrupting shallow lake feedback loops and offer insights for turbid-state lake restoration.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Evaluating effectiveness of flocculation and wave-reduction barriers for restoration of a turbid, terminal lake
Series title Wetlands Ecology and Management
DOI 10.1007/s11273-025-10094-9
Volume 33
Publication Date October 14, 2025
Year Published 2025
Language English
Publisher Springer Nature
Contributing office(s) Oregon Water Science Center
Description 82, 16 p.
Country United States
State Oregon
Other Geospatial Malheur Lake
Additional publication details