ASSESSMENT OF LONG-TERM GROUNDWATER LEVEL RECORDS IN WISCONSIN FROM 1937-2017

This study examines long-term groundwater level records in Wisconsin, and investigates potential relationships between regional groundwater trends and climate variability. Monthly groundwater level data from the U.S. Geological Survey (USGS) were gathered for wells varying in aquifer type across the state of Wisconsin. Monthly outputs of Wisconsin state and division climate data were obtained from the Midwestern Regional Climate Center (MRCC). To be considered for analysis, well records were required to span at least ten years and contain fewer than 15% omissions. Well sites were then grouped by aquifer type and climate zone (consistent with MRCC) for analysis. Out of 20 total wells, 11 are in sand and gravel, six are in the Cambrian-Ordovician aquifer (sandstone), and three are in the Silurian-Devonian aquifer (carbonates). Well sites are distributed amongst climate divisions, with two well sites in zone 1 (NW), two in zone 2 (N. Central), two in zone 3 (NE), two in zone 5 (Central WI), one in zone 6 (E. Central), three in zone 7 (SW), four in zone 8 (S. Central), and four in zone 9 (SE). Well records in southwest and south-central Wisconsin (climate zones 7 and 8) are predominantly from the Cambrian-Ordovician aquifer and show increasing groundwater level trends from 1960-2017, with gradients ranging from 0.04 to 0.22 ft/yr. Conversely, southeast Wisconsin (climate zone 9) shows declining long-term groundwater levels from 1947-2017, with gradients ranging from 0.004 to 0.06 ft/yr.