Improvement of Wisconsin Groundwater Monitoring Network

Introduction: Reliable water-level measurements are essential for understanding groundwater flow systems and recharge/discharge processes and for managing Wisconsin groundwater resources. The water-supply and well-construction industries and agriculture all have need for these data. Information regarding groundwater movement derived from observed fluctuations of the water table also are useful in determining the fate of contaminants in groundwater-quality studies.

The Wisconsin Geological and Natural History Survey (WGNHS) and the U.S. Geological Survey (USGS) have maintained and operated a statewide groundwater observation-well network for collecting water-level measurements since 1946. The network design, objectives, and history are described in Wisconsin Groundwater Observation-Well Network, 1946-95 (Zaporozec, 1996). Water-level measurements and associated geologic and well construction data are stored in a computer data base, and are available to the public upon request.

Evaluation and use of the data from some older observation wells has been limited by a lack of basic well-construction information. Also, the amplitude of water-level fluctuations has declined in some of these older wells that are open to shallow sand-and-gravel deposits. This indicates that these wells may have gradually developed a poor hydraulic connection with the surrounding — aquifer material. Therefore, in January 1994 and in December 1996, the WGNHS, in cooperation with the USGS, proposed studies to run geophysical logs and conduct hydraulic tests on selected network wells that had little or no well-construction data or were suspected to be in poor hydraulic connection with the surrounding aquifer. The proposed studies were funded by the Wisconsin Department of Natural Resources (DNR) and through the State of Wisconsin joint solicitation for project proposals to conduct research and monitoring on groundwater (DNR project No. 118 and 135, respectively).