Hydrogeology research at IGS is focused on evaluating groundwater conditions in shallow and deep aquifers across Iowa and bridging the intersection of groundwater quantity and quality with societal needs. We work closely with the Iowa Department of Natural Resources (IDNR) and water suppliers across the state to assess groundwater aquifers, develop local and regional scale models and define critical source areas for groundwater protection.
Capture Zone Studies: For example, many public wells in Iowa are threatened by nitrate concentrations approaching the maximum contaminant level of 10 mg/l. IGS hydrogeologists conduct research to better define priority acres for best management and conservation practices to reduce nitrate levels in public wells. One important part of this work involves the collection of hydrogeologic data used to develop and calibrate groundwater flow models to more accurately define wellfield capture zones. Using field methods including well installations, geophysics and modeling, IGS hydrogeologists evaluate the vertical and lateral extent of an aquifer, permeability and storage within an aquifer, groundwater flow direction and gradient, and sources of nitrate impacting a public water supply. Based on this type of work, the extent of groundwater capture zones has been better defined, some areas have been reduced by as much as 90 percent. Improving capture zones allow future best management practices to be installed in targeted acres for improved long-term water quality. For example, an accurate capture zone developed by IGS hydrogeologists at Plainfield, Iowa was used to convince 100 percent of the landowners within the capture zone to participate in best management practices. Implementing IGS research at public water supplies provides an enormous opportunity to significantly reduce the nitrate concentrations in public drinking water supplies in a relatively short period of time.
Groundwater Travel Times and Age Dating: The age of groundwater within an aquifer and the time it takes for groundwater to move in aquifers and confining beds are critical research questions for Iowans. IGS researchers are evaluating groundwater conditions in a variety of geologic settings to unravel the mysteries of groundwater ages and travel times. For example, IGS researchers used isotopic age dating to provide an indication of the groundwater age in two deep aquifer systems in Iowa: the Cambrian-Ordovician aquifer and the Manson Impact Structure. In both studies, groundwater was found to be exceptionally old, on the order of several tens to more than one hundred thousand years
Groundwater modeling and isotopic age dating indicated that the groundwater age in the Cambrian-Ordovician aquifer was more than 10,000 years old. Study results were published in:
Schilling, K.E., P.J. Jacobson, R.D. Libra, J.M. Gannon, R. Langel and D. Peate. 2017. Groundwater age in the Cambrian-Ordovician aquifer in Iowa. Environmental Earth Science, 76:2 DOI 10.1007/s12665-016-6321.
Groundwater Travel Times in Agricultural Watersheds: An area of hydrogeology research interest at IGS is developing a better understanding of the time it takes for groundwater to move in agricultural watersheds and the lag time needed for groundwater to respond to land use change. IGS researchers worked closely with IDNR GIS specialists to develop a groundwater travel time model to evaluate groundwater travel times in a southern Iowa watershed and in a tile-drained basin in central Iowa. At the Walnut Creek watershed in Jasper County, IGS hydrogeologists estimated the groundwater travel time in the basin to be approximately 10 years and found general agreement among different methods.
In another IGS-led study, researchers have quantified how groundwater travel times are changed through tile drainage.
The time it takes for groundwater to respond to land use change has been investigated at the Neal Smith National Wildlife Refuge in Jasper County, Iowa. At the refuge, row crop lands are being replaced with native prairie and IGS researchers are monitoring conditions during the restoration process. Results are showing that land use change from crop to grass reduced groundwater nitrate concentrations by approximately 0.5 to 1 mg/l per year following restoration.
Overall, hydrogeological research conducted at IGS is critical for Iowans to better understand groundwater conditions in shallow and deep aquifers across Iowa. IGS staff welcomes research ideas and collaboration on these topics and other hydrogeological questions and issues that impact Iowans.