Mounting evidence suggests that traditional stormwater mitigation and treatment approaches targeting only pollutant loading and flow moderation are not sufficient to achieve overall desired water quality benefits in urbanized, coldwater habitats. Temperature, as one of the key environmental variables controlling aquatic biota, must also be considered in stormwater management planning where urban runoff is introduced into aquatic systems. As runoff passes over dark-colored, impervious surfaces, its temperature increases. The resultant thermal warming in receiving streams by heated stormwater in summer months is often overlooked and even exacerbated by traditional methods of stormwater collection.
Kieser & Associates is leading a five-year thermal enrichment study, supported in-part by the Water Environment Research Foundation (WERF) and the Kalamazoo Foundation Environment Now Fund, at the Consolidated Drain site in Portage, Michigan. The Consolidated Drain is the single largest stormwater discharge to Portage Creek. Portage Creek, a tributary to the Kalamazoo River, is a designated coldwater trout stream. The hypothesis of this project is that stormwater systems can be designed to eliminate major alterations to the stream ecology due to thermal enrichment through enhancement or substitution of traditional design and Best Management Practices (BMPs). This hypothesis is being tested through monitoring and evaluation of the hydrologic and thermal regime of the Consolidated Drain system and the receiving stream, Portage Creek, both before and after the installation of this system known as the Regional Stormwater Treatment and Trailways Facility.

Continuous monitoring of the hydrologic and thermal conditions of the drain has taken place since spring of 1999. Water temperature, rainfall, stream flow, air temperature, relative humidity, and incoming solar radiation have all been measured at various locations throughout the study area using sensitive recording devices. These data will provide valuable insight into how the alterations to the drain will affect the temperature of the water reaching Portage Creek.

The three objectives of this research include:

  • Confirming the relationships between disrupted heat budgets found in urban areas and local hydrology;
  • Quantifying the impacts of thermally enriched stormwater discharges on coldwater temperature regimes as related to their influence on aquatic life and habitat; and
  • Determining design criteria for stormwater BMPs and controls necessary to mitigate problems associated with stormwater thermal enrichment.

One of the most important features of this project will be the development of transferrable assessment tools, evaluation protocols and stormwater Best Management Practices (BMPs) for other locations where urbanization continues to encroach upon and impair aquatic habitats.