The U.S. Geological Survey, at the request of Congress, is assessing the availability and use of the Nation’s water resources to help characterize how much water is available now, how water availability is changing, and how much water can be expected to be available in the future. The Great Lakes Basin Pilot project of the U.S. Geological Survey national assessment of water availability and use focused on the Great Lakes Basin and included detailed studies of the processes governing water availability in the Great Lakes Basin. One of these studies included the development of a groundwater-flow model of the Lake Michigan Basin. This report describes the compilation and estimation of the groundwater withdrawals in those areas in Wisconsin, Michigan, Indiana, and Illinois that were needed for the Lake Michigan Basin study groundwater-flow model. These data were aggregated for 12 model time intervals spanning 1864 to 2005 and were summarized by model area, model subregion, category of water use, aquifer system, aquifer type, and hydrogeologic unit model layer.
The types and availability of information on groundwater withdrawals vary considerably among states because water-use programs often differ in the types of data collected and in the methods and frequency of data collection. As a consequence, the methods used to estimate and verify the data also vary. Additionally, because of the different sources of data and different terminologies applied for the purposes of this report, the water-use data published in this report may differ from water-use data presented in other reports. These data represent only a partial estimate of groundwater use in each state because estimates were compiled only for areas in Wisconsin, Michigan, Indiana, and Illinois within the Lake Michigan Basin model area. Groundwater-withdrawal data were compiled for both nearfield and farfield model areas in Wisconsin and Illinois, whereas these data were compiled primarily for the nearfield model area in Michigan and Indiana.
Overall water use for the selected areas in Wisconsin, Michigan, Indiana, and Illinois was less during early time intervals than during more recent intervals, with large increases beginning around the 1960s. Total estimated groundwater withdrawals for model input range from 18.01 million gallons per day (Mgal/d) for interval 1 (1864–1900) to 1,280.25 Mgal/d for interval 12 (2001–5). Withdrawals for the public-supply category make up the majority of the withdrawals in each of the four states. In Wisconsin and Michigan, the second largest withdrawals are for the irrigation category; in Indiana and Illinois, industrial withdrawals account for the second largest withdrawal amounts. The smallest withdrawals are for miscellaneous uses in Wisconsin and irrigation uses in Indiana and Illinois.
Estimated groundwater withdrawals in the Southern Lower Peninsula of Michigan, Northeastern Illinois, and the farfield model area are generally larger than in the other model subregions. Withdrawals in Michigan and Indiana are predominantly from the Quaternary aquifer system, whereas withdrawals in Illinois are predominantly from the Cambrian-Ordovician aquifer systems. Withdrawals in Wisconsin are about equal from the Quaternary and Cambrian-Ordovician aquifer systems. Estimated groundwater withdrawals in Michigan and Indiana are predominantly from the unconfined unconsolidated aquifer type. Withdrawals in Illinois are largely from the deep confined bedrock aquifer type, although they decreased considerably in more recent time intervals. Wisconsin withdrawals are about equal from unconfined unconsolidated and deep confined bedrock aquifer types.
Groundwater-withdrawal estimates in Wisconsin were compiled for the 47 easternmost counties within the boundary of the Lake Michigan Basin model, of which 32 counties, though not entirely contained, are at least partly within the Lake Michigan Basin. Overall, 6,457 withdrawal locations were estimated in the Wisconsin part of the Lake Michigan Basin model area, and 5,151 locations were active in the last time interval (2001–5) for a total groundwater withdrawal of 476.51 Mgal/d. Total withdrawals for the nearfield model area increased consistently from 1.84 Mgal/d in time interval 1 (1864–1900) to 192.88 Mgal/d in interval 12 (2001–5); farfield model area withdrawals increased from 1.35 Mgal/d in interval 1 to 283.63 Mgal/d in interval 12. Withdrawals by nearfield model subregions for interval 1 to interval 12 increased from 0.82 Mgal/d to 118.59 Mgal/d in Northeastern Wisconsin and from 1.02 Mgal/d to 76.57 Mgal/d in Southeastern Wisconsin, with the exception of interval 10 (1986–1990).Groundwater-withdrawal estimates in Michigan were determined for those counties in Michigan with at least some part within the boundaries of the basin, plus Monroe County. Overall, there were 2,046 withdrawal locations estimated for counties within the Lake Michigan Basin model area, and 1,860 locations were active in the last time interval (2001–5) for a total withdrawal of 397.72 Mgal/d. Estimated withdrawals for the nearfield model area range from 7.43 Mgal/d in time interval 1 (1864–1900) to 359.91 Mgal/d in interval 12 (2001–5); farfield model area withdrawals range from 0.63 Mgal/d in interval 1 to 37.81 Mgal/d in interval 12. Estimated withdrawals by nearfield model subregions for interval 1 to interval 12 range from 7.21 Mgal/d to 306.15 Mgal/d in the Southern Lower Peninsula, 0.22 Mgal/d to 44.83 Mgal/d in the Northern Lower Peninsula, and 0 to 8.94 Mgal/d in the Upper Peninsula.
Groundwater-withdrawal estimates in Indiana were determined for 11 counties in the Northern Indiana subregion, all of which have at least some part within the Lake Michigan Basin boundary. Overall, a total of 2,002 withdrawal locations were estimated for these counties, and 1,104 locations were active in the last model time interval (2001–5) for a total withdrawal of 128.3 Mgal/d. Total withdrawals in Indiana for the nearfield model area range from 0.21 Mgal/d in interval 3 (1921–40) to 117.42 Mgal/d in interval 12 (2001–5), and withdrawals from the farfield model area range from 0 Mgal/d in interval 3 to 10.88 Mgal/d for interval 12.
Groundwater-withdrawal estimates in Illinois were determined for three distinct blocks of time (1864–1964, 1964–1979, and 1979–2004) based on how the data were inventoried. The groundwater-withdrawal data from before 1964, corresponding to model time intervals 1 through 5 (1864–1960) and part of interval 6 (1961–1970), were summarized for seven major pumping centers in the nearfield model area (which is also the Northeastern Illinois subregion). Water-use estimates from 1964 to 2004 were assigned to intervals 6 through 12 (1961–2005) for the 40 counties in the Illinois Lake Michigan Basin model area. In the nearfield model area, withdrawals range from 6.76 Mgal/d in time interval 1 (1864–1900) to 301.71 Mgal/d in interval 8 (1976–80), then decrease to 166.93 Mgal/d in interval 12 (2001–5).