Applying Science to Locate Groundwater

Homeowners, well drillers, farmers, miners, corporations, developers, and municipalities around the state are some of those who contacted the ISGS with water concerns during the past year. Because water supplies in Illinois generally are adequate, people tend to take water availability for granted. Residential, industrial, or municipal projects can be well under way before people realize they don't have the water they need. Fortunately, others plan ahead, but they may seek ISGS assistance to determine the feasibility of their project based on water availability. Finding new groundwater supplies in the quantities necessary to meet the needs of Illinois' growing population is an ongoing challenge for the geologists in the Survey's Groundwater Geology Section.

Because ISGS geologists understand the origin of geologic materials and map their distribution, they often can help identify where groundwater is likely to be found. Aquifers, the sand and gravel deposits that supply water, are not always easy to find. Sometimes their location is masked by complex layers of glacial deposits, and, even when sand and gravel deposits are located, they don't always yield water.

Using information gleaned from the Survey's extensive reference materials, including well records, geologic maps, water-quality analyses, downhole geophysical logging records, surficial geophysical survey records, and core logs, ISGS geologists can provide information about the water availability in an area, its general location, and formation depth and trend. The geologists may also be able to give advice about whether a large- or small-diameter well is needed and what kind of screen or casing should be used.

The value of the Survey's collective scientific knowledge is emphasized when the cost of drilling is considered—it may cost a homeowner $7 a foot, or $1,176, to drill a 168-foot dry hole, an expense that may be avoided by consulting ISGS experts prior to drilling. Where geologic materials have great variability, making it more difficult to find groundwater, electrical earth resistivity surveys can help pinpoint where water exploration efforts should begin, reducing drilling costs.

Water location efforts are one example of how ISGS geologists apply scientific knowledge to solve real-world problems on a daily basis, responding to numerous groundwater information requests from individuals, government bodies, and businesses. Survey scientists also provide general information in the form of circulars, bulletins, and other written materials.