Seventy-five percent of all Iowans rely on groundwater as their drinking water source. Groundwater is one of the better understood water resources in Iowa, yet much remains unknown. The objective of the groundwater monitoring network is to describe and measure groundwater quality throughout Iowa, characterize aquifers in different hydro-geological environments, and measure water quality changes and identify trends in Iowa's aquifers. The information gathered through this program can be used to assess the groundwater resource, project future conditions of supply, address contamination concerns, and provide the information necessary to effectively manage the resource.
Information about Iowa's groundwater is being gathered through a groundwater level network, a ground water quality network, development of a monitoring well network, and private well-water monitoring.
Groundwater Level Network
Since 1982, the Iowa Department of Natural Resources and the U.S. Geological Survey have cooperatively conducted the Iowa Groundwater Level Network. The objectives of the groundwater level network are: to collect data documenting any change in groundwater storage over time in the principal aquifers; to provide both long-term and short-term data necessary to assess and predict the response of hydrologic systems to natural climatic variations and human-induced stresses; to quantify the hydrologic characteristics of aquifers including transmissivity, hydraulic conductivity, and specific capacity; and to provide historical baseline data for studies of Iowa's aquifers.
The current groundwater level network in Iowa consists of 175 wells completed in the principal bedrock and surficial aquifers that supply groundwater to numerous users throughout the state. The advantage of the groundwater level network is that static water levels for principal aquifers can be monitored through time, generally under non-pumping conditions. Water levels are measured on a quarterly to monthly basis and entered into the USGS Groundwater Site Inventory database. The majority of wells are monitoring wells, while some are municipal wells. Each year, a selected aquifer and its respective wells are reevaluated to determine which wells to continue to monitor and whether additional wells in that aquifer should be included in the groundwater level network. The aquifers monitored are Alluvium, Pleistocene, Cretaceous, Mississippian/Pennsylvanian, Silurian/Devonian, and Cambrian/Ordovician.
Network data collected from all aquifers are compiled and published in the annual U.S. Geological Survey Water-Resources Data, Iowa report. The U.S. Geological Survey Open-File Report 92-27 titled "The Ground-Water-Level Monitoring Network in Iowa" was published in 1992 and describes in detail the groundwater level network in Iowa. To request a copy of the publication, contact the U.S. Geological Survey at (319)337-4191.
Groundwater Quality Network
The Iowa Department of Natural Resources, U.S. Geological Survey, and University of Iowa Hygienic Laboratory have conducted the Iowa groundwater quality monitoring program since 1982. The purpose of the program is to provide consistent and representative data describing the chemical water quality of the principal aquifers in Iowa and to determine possible spatial or temporal trends in water quality.
The groundwater monitoring program was initiated to continue a program begun in 1950 by the State Health Department that consisted of periodic, nonspecific sampling of untreated water from municipal water supply wells. Currently, a core of 90 municipal wells are sampled each year. An 60 additional municipal wells from particular aquifers are sampled each year on a rotating basis. The rotating wells will allow an in-depth investigation into the water quality of each primary aquifer in the state.
Ambient (Dedicated) Groundwater Monitoring Network
The Water Monitoring Section of the Iowa Department of Natural Resources started the Dedicated Groundwater Monitoring Network to improve their ability to monitor frequently used aquifers across the state. These wells are solely dedicated to monitoring groundwater quality in aquifers used by citizens and municipalities. The first well nest of 3 wells was drilled in May 2001 into the Mississippian Aquifer at Briggs Woods Park in Hamilton County. In January 2002, a second well nest of 5 wells was completed in the Mississippian Aquifer at Rutland Marsh in Humboldt County. Another well nest of 3 wells was completed in February 2003 in the Silurian Aquifer at Westfield Elementary School near the city of Robins in Linn County.
These "well-nests"- two or more wells located in close proximity to each other where each well is completed to a different depth, are monitored to evaluate the ambient quality of aquifers in Iowa.
Development of monitoring wells will provide important information for the overall management of groundwater in Iowa. Pump tests and geophysical tests will assess aquifer characteristics. A continuous rock core will be obtained from each site as part of a lithologic and stratigraphic reference collection. This information will enhance our understanding about the distribution and variability of rock units throughout the state, and their potential as future or expanded sources of groundwater for Iowans.
The advantage of a monitoring well network is that the well construction is well known, the rock core provides detailed information about the sequence of bedrock in the subsurface, allows determination of aquifer properties and water quality from a specific aquifer under non-pumping conditions.
Other Groundwater Monitoring Programs
- Rural Well Water Survey
The State-Wide Rural Well-Water Survey (SWRL) was a one-time, statistically based sampling of 686 private wells across Iowa to evaluate the quality of private drinking-water supplies used by rural Iowans. The survey, completed in 1988 and 1989, addressed two questions: (1) What proportion of private wells in rural Iowa are affected by various environmental contaminants? (2) What proportion of rural Iowa residents are utilizing well water containing these environmental contaminants? The survey was conducted as part of the implementation of the Iowa Groundwater Protection Act of 1987. Water sampling was conducted by the Iowa Department of Natural Resources and the University of Iowa Center for Health Effects of Environmental Contamination. Results provide a 'snapshot' of the condition of the private well-water supplies in Iowa and some insight into the condition of Iowa's groundwater resource. It also serves as a baseline for measuring future trends and changes in groundwater and rural private drinking-water quality. The well-water was analyzed for an extensive list of parameters, including pesticides, bacteria, inorganic chemicals, and radionuclides. An inventory questionnaire was completed for each household and a health assessment questionnaire was completed for each individual in the household.
- Private Wells