Excerpt
In 2001, among the rolling green hills of south-central Wisconsin, Dane County passed an Erosion Control and Stormwater Management Ordinance. It requires temperature reduction practices for most development projects that drain to a cold-water stream.
The purpose of the ordinance stems from the fact that the thermal impact of urbanization can be detrimental to aquatic life in cold-water streams. Streams in urbanized watersheds generally tend to show increased diurnal and seasonal stream temperature fluctuations compared to streams in less developed areas (Pluhowski, 1970; Klein, 1979). Heated runoff from impervious surfaces has some responsibility for this effect. Other factors associated with urbanization that contribute to increased stream temperature fluctuations include the removal of riparian vegetation, the widening of stream channels, and the reduction in groundwater inflow to streams.
Impervious surfaces, such as concrete, typically absorb and store solar radiation better than natural surfaces, so they usually are warmer, especially during the summer months. Summer afternoon thunderstorms can cause a direct thermal loading on urban streams because the impervious surfaces transfer some of their heat to precipitation. This heated water then moves quickly over the impervious surfaces and through drainageways to nearby streams, giving it little chance to cool …
Footnotes
Kathleen E. Arrington is senior research technologist in the Department of Crop and Soil Sciences at the Pennsylvania State University, in State College, Pennsylvania. Stephen J. Ventura is a professor of Soil Science and Environmental Studies and John M. Norman is professor of soil science with the Department of Soil Science at the University of Wisconsin-Madison, in Madison, Wisconsin. Aicardo Roa-Espinosa is an urban conservationist with the Dane County Land Conservation Department in Madison, Wisconsin.
- Copyright 2003 by the Soil and Water Conservation Society
This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.