Beginning in 1991, the NAWQA Cycle 1 study design for ground water focused on assessing the water-quality conditions of major aquifers in the United States with emphasis on the quality of recently recharged ground water associated with present and recent human activities. Following the NAWQA design, ground-water quality is assessed by three primary study components:
- Major Aquifer Studies (previously called “Study-Unit Surveys”): Designed to assess the water quality of the major aquifers of each Study Unit by sampling primarily existing wells. For a description of aquifers underlying the Western Lake Michigan Drainages, click here.
- Land-Use Studies: Designed to use observation wells and selected existing wells to assess the quality of recently recharged shallow ground water associated with regionally extensive combinations of land use and hydrogeologic conditions.
- Flowpath Studies: Designed to use transects and groups of clustered, multilevel observation wells to examine specific relations among land-use practices, ground-water flow, contaminant occurrence and transport, and surface- and ground-water interaction.
In the Western Lake Michigan Drainages, two major aquifer studies, two land-use studies, and two flowpath studies have been conducted since 1991. Major aquifer studies were conducted in the Cambrian-Ordovician and the Glacial Deposits aquifers. The two land-use studies focused on agriculture (corn/alfalfa rotation) in different hydrogeologic settings (sand and gravel versus till). The flowpath studies were nested within each of the land-use study areas.
Starting in 2001 with Cycle 2, NAWQA designated some of its ground-water networks to be used for long-term analysis of trends in water quality. In WMIC, the Cambrian-Ordovician major aquifer study and sand and gravel land-use study were chosen to be part of this trend network. On decadal intervals, the full network of wells (typically 30 wells) in both of these study areas is to be sampled. Additionally, a subset of wells from each network, chosen to represent the water-quality of the entire network, is to be sampled more frequently (biennially and quarterly). The decadal, biennial, and quarterly sampling strategy is designed to help understand the factors that affect long-term and short-term trends and seasonal variability in ground-water quality.
For full details of each ground-water study conducted in the Western Lake Michigan Drainages, please click on one of the study components above. Water-quality data for individual wells included in all of the WMIC ground-water studies is available online under Data.
For more information about ground water and aquifers, please visit: http://water.usgs.gov/ogw/