An Investigation of the Hydrogeological Conditions Responsible for Springs in a Glaciated Terrain

Introduction: Within Dane County, Wisconsin numerous springs exist in and around the Nine Springs watershed, the Token Creek watershed, Pheasant Branch Creek, the Sugar River watershed, and Garfoot Creek (WRM, 1996; WRM, 1997). The springs are poorly understood, but there is growing public interest in how the springs will be affected by urban development and increases in municipal pumping. Groundwater flow models are often useful in addressing questions pertaining to changes in the hydrologic budget of a system. The Dane County regional groundwater flow model (Krohelski et al., 2000) provides a valuable starting point from which to create watershed-scale models in the county, which would be better suited to addressing questions related to spring flow. However, until the geologic features and hydrogeologic system responsible for the springs are better understood, the springs cannot be accurately incorporated into watershed-scale models.

The research completed under Wisconsin Department of Natural Resources (WDNR) funding involved a combination of field and numerical modeling exercises intended to test several conceptual models of the geologic features and mechanisms controlling spring flow in the Nine Springs watershed (Figure 1) and similar glaciated terrains. Fieldwork included the installation of two deep groundwater monitoring wells and continued water quality monitoring of the established shallow groundwater monitoring network within the watershed (Bahr et al., 1999). The well installations provided the opportunity to characterize the bedrock units in the immediate vicinity of the springs through lithologic description, geophysical logging, and hydraulic testing using straddle packers.