Over seventy-five percent of Iowans rely on groundwater as their primary source of drinking water. Assessments of Iowa’s groundwater quality and quantity are necessary to address public health concerns, help communities, industries, individuals, and ecosystems meet their water needs, and ensure the sustainability of this resource. Groundwater monitoring efforts have benefitted from collaboration between numerous groups, including the IDNR’s Water Monitoring Section, the Iowa Geological Survey (now a part of the University of Iowa’s Institute for Hydraulic Research), the US Geological Survey (USGS), the State Hygienic Laboratory (SHL), the Center for Health Effects of Environmental Contaminants (CHEEC), municipal water operators, state parks, county conservation boards, and well drillers.
Ambient Groundwater Quality Monitoring
Objectives of Iowa’s ambient groundwater quality monitoring program are as follows:
1) To characterize the quality of groundwater by aquifer and region.
2) To evaluate long-term trends in groundwater quality.
3) To assess new or emerging issues of groundwater quality concern.
Seven major aquifer groups provide water for Iowans: alluvial aquifers, sand & gravel aquifers, Cretaceous (Dakota) sandstone, Silurian-Devonian bedrock, Mississippian bedrock, Pennsylvanian bedrock, and Cambrian-Ordovician bedrock (the Jordan Aquifer). To achieve the objectives listed above, the “core 90,” a set of representative municipal wells, were regularly sampled from 1982-2006, then again in 2012. In late 2014/early 2015, samples were collected from a subset of these wells expected to to be vulnerable to surface contamination. Raw water samples have been analyzed for several groups of contaminants, including basic water quality parameters, nutrients, pesticides, dissolved metals, volatile organic compounds (VOC’s), radionuclides, atrazine and chloroacetanilide herbicides and their degradates, and pharmaceutical compounds. Groundwater data has previously been accessed using the IASTORET application, and efforts are currently underway to migrate data into an EQuiS database. These and other historical groundwater data have also been included in a geodatabase which is available on the NRGIS library (under state-wide data/hydrologic/ground waters), along with contoured water quality data layers for select bedrock aquifers.
IDNR has collaborated with academic institutions, federal and state agencies, and others to conduct the following groundwater quality studies:
- Iowa Groundwater Survey: 2013. This survey of 66 public water supply wells looked at a wide range of parameters, including viruses and pharmaceuticals. A plant virus (pepper mild mottle virus) that is considered a possible indicator of human or animal waste was detected at low concentrations in 17% of the wells studied, and caffeine was detected in 25% of the wells. Mixtures of up to 6 pesticides or pesticide degradate compounds were found in some wells. Well vulnerability defined by confining layer thickness was determined to be a good predictor of nitrate and pesticide contamination, but not viruses or pharmaceuticals. Full Report
- Statewide Rural Well Water Survey Phase 2 (SWRL2): 2006 – 2008. SWRL2 sampled 473 private wells in Iowa, located in 89 of the state’s 99 counties. The wells included 116 wells sampled in the original SWRL study, with the remainder being mainly wells drilled since SWRL. The contaminants analyzed for this study included nitrate, total coliform bacteria, arsenic, atrazine, and herbicides, including chloroacetanilide degradates.
- Statewide Rural Well Water Survey (SWRL): 1988 – 1989. SWRL was a statistically designed, population-based sampling of private wells in Iowa, designed to assess the exposure to nitrates, bacteria, and commonly-used herbicides. SWRL sampled 686 wells during 1988-89, in all counties of the state.
- Iowa Community Private Well Study: 2003. While SWRL focused on private wells in unincorporated areas, this 2002 study sampled private wells in communities without a public water supply. The study included a random sampling of wells and a component focused on communities with multiple potential contaminant sources. The results of the study indicated these private “in-town” wells exhibit generally similar levels of contamination as rural private wells. 2004 Factsheet
- Impacts of Earthen Manure Storage Structures: 1994 – 2006. 1998 Report
- Floyd-Mitchell Study on the Impacts of Agricultural Drainage Wells: 1984 – 2008. 2002 Report
- Big Spring Monitoring Study 2002 Retrospective
Links to recent studies will be posted when they are made available. Reports completed by the Iowa Geological Survey can be found at the IGS Publications website hosted by IIHR.
For more information, contact: Claire Hruby, Geologist ph: 515.725.8202 email: email@example.com