Willow Creek Watershed Stormwater Monitoring

Steve Schubert, Biological Programs Manager, conducted stormwater monitoring in the Willow Creek watershed in Sheboygan, Wisconsin from November 2025 to April 2026. The purpose of the sampling was to collect surface water data for chloride, specific conductance, and temperature at six sites within the Glacial Lakes Conservancy’s (GLC) Willow Creek Preserve. Two sites were on the mainstem, one site was on a first order tributary to Willow Creek, and the other three sites were at stormwater outfalls that received road and parking lot runoff. This watershed has a healthy riparian buffer, but stormwater inputs of deicing chemicals (e.g., road salt) during the winter can short-cut that buffer and result in unhealthy chloride levels that can adversely affect the aquatic benthic invertebrates in Willow Creek.

This study identified elevated chloride levels in Willow Creek that resulted from stormwater runoff, that at times, exceeded Wisconsin’s surface water quality standard for aquatic life protection. The maximum chloride concentration found at the stormwater outfalls was 2,060 mg/L. The maximum standard conductance value was 6,872 uS/cm. This study demonstrated that excess chloride in runoff may be problematic to the aquatic communities in the watershed. GLC is planning to install continuous sensors to better understand the fate and transport of chloride next winter. Outreach to educate local property owners on the best use of deicing chemicals is also occurring.

Example of a stormwater outfall in the Willow Creek watershed

Stormwater sampling using a multi-parameter field probe in a stormwater outfall