Iowa Groundwater-Quality Monitoring Program
NEED FOR STUDY:
Groundwater quality is one of the most critical resource concerns in the State of Iowa. A groundwater-quality monitoring program is needed to provide data to aid State and local management and protection agencies to effectively evaluate the groundwater resources of the State.
The primary purpose of the groundwater-quality monitoring program is to provide consistent and representative groundwater-quality data that describe the chemical quality of groundwater resources in the State. Initially, the primary objective was to specifically describe the baseline groundwater-quality of the major aquifers in the State that are stressed by intensive use, contamination, or deteriorating quality. Since water year 1992, greater emphasis has been placed on determining trends in groundwater quality and correlating water quality with possible contributing factors such as location, land use, aquifer, aquifer depth, and precipitation.
As of 1992, ninety wells completed in the principal aquifers of the State have been selected for sampling to determine possible trends in groundwater quality. Wells completed in surficial and vulnerable bedrock aquifers were sampled on one- or two-year rotational schedule, respectively. Bedrock wells not vulnerable to contamination were sampled every four years. All wells were sampled for major ions, nutrients, and common herbicides. Additionally, shallow wells (less than 300 feet deep) were sampled for selected priority pollutants, and deep wells (more than 300 feet) were sampled for radionuclides. In 2001, the sampling rotation was suspended in favor of sampling all 90 wells on an annual basis. In 2002, an additional 60 wells were included in the overall sampling strategy in an effort to better define trends in the chemical quality of water by aquifer. Beginning with the Mississippian-Cretaceous aquifers in 2002, a different set of aquifers will be targeted for additional random sampling each year on a rotating basis. Network data are typically compiled and published in the annual U.S. Geological Survey Water Resources Data, Iowa report. In addition, Open-File-Report (OFR) 98-3 "Quality of groundwater used in selected municipal water supplies in Iowa, 1982-1996" by Bryan D. Schaap and S. Mike Linhart was published in 1998. Copies are available for distribution. The report reviews the water-quality data since the program's inception in 1982 and provides basic statistics by county, aquifer, and well depth. A CD-ROM of the entire data set accompanies the report. Sampling results for 1997-2002 water years are published in the USGS Iowa District Annual Report Series.