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Spatio-temporal Relationship between Groundwater Recharge and Urbanization:
Waukesha County, Wisconsin
Ulrike Galasinski, University of Wisconsin – Milwaukee, Milwaukee, WI, ug@uwm.edu
Woonsup Choi, University of Wisconsin – Milwaukee, Milwaukee, WI, choiw@uwm.edu
Chulsue Hwang, Kyung Hee University, Seoul, Korea, hcs@khu.ac.kr
The decline in groundwater level within Waukesha County, located in southeastern
Wisconsin, was analyzed in regards to the degree of urbanization in the county. Utilizing a
geographic information system, US Geological Survey’s potentiometric surface level data
were compared to the permeability of the subsurface ranging from low to high in Waukesha
County and detailed land use data through multiple overlay operations. The produced maps
indicate that low potentiometric surface levels usually intercept with either areas of low
permeability or areas of increasing urbanization. A statistical analysis confirmed that the
degree of urbanization which corresponds to the extent of impervious urban surfaces is
significant in explaining the decline of potentiometric surface in Waukesha County between
1900 and 2000. A trend analysis of total annual precipitation data from two weather stations in
Waukesha County confirmed that an increase in precipitation during the last several decades
did not outweigh the groundwater decline due to human activity in the high permeability zone.
Additionally, USGS data regarding groundwater withdrawal showed that groundwater
extraction was high in areas where natural recharge is diminished through low subsurface
permeability. A correlation analysis showed that in areas of low subsurface permeability
potentiometric surface level and total groundwater withdrawals have a strong significant
correlation while in areas of high subsurface permeability potentiometric surface and the
degree of urbanization show a strong significant correlation.
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