Analysis of Groundwater Level Changes, Surface Water Conditions, and Water Use in the Greater Barrington Region, 2014–2019

The Barrington area is dependent on shallow groundwater resources for water supply and is unusual in that much of the water demand required by its residents is met by private wells as opposed to centralized community water systems. The Barrington Area Council of Governments (BACOG) supports a groundwater and surface water monitoring program consisting of continuous and periodic water level measurements in local streams and in the shallow sand and gravel aquifer system (Henry Formation). BACOG also leads a yearly mass measurement of water levels at municipal wells within and surrounding the BACOG study area. We developed potentiometric surfaces (maps that represent aquifer water level elevations) for the sand and gravel aquifer system for the years 2014–2019 using geographic information system (GIS) interpolation tools, and from those developed potentiometric change maps. We also analyzed trends in baseflow conditions using United States Geological Survey (USGS) streamgage data and water use from the sand and gravel and shallow bedrock aquifers using Illinois Water Inventory Program (IWIP) data. The potentiometric surfaces show a consistent groundwater high in the western half of the BACOG study area due to the Henry Formation being at or near the land surface. Resultsfrom this study indicate that water levels in the sand and gravel aquifer within the BACOG study area have generally increased over the five-year study period. Water levels increased on average: 1) by around 5 feet at the continuously monitored USGS sites, 2) by 5.8 feet at the Illinois State Geological Survey monitoring wells, and 3) by over 5 feet at municipal wells. Baseflow alsotrended upward at the Fox River and Poplar Creek streamgaging sites. Regional municipal water use from the sand and gravel aquifer decreased from 16 million gallons per day in 2005 to around 13 million gallons per day in 2018. The increase in water levels may be due to a combination of less municipal water use, above average precipitation, and improved household water use efficiency. Because of the projected increases in precipitation intensity, flooding events, and climate variability, we recommend the continuation of BACOG’s groundwater monitoring program to understand long-term (decadal) trends in groundwater levels to support long-term regional planning of water supplies. Because of the predominance of private wells in the region and that a significant portion of the aquifer is susceptible to contamination, we also recommend that groundwater quality sampling be a focus of future BACOG studies.