The USGS National Water Quality Assessment (NAWQA) program conducts water-quality assessments in major river basins and aquifers across the country. Major river basins and aquifers are referred to as NAWQA “study units”. Assessments are done in cycles, where selected sets of study units are sampled intensively for three years followed successively by another 2 groups of study units. Once intensive sampling in all three groups of study units has been completed, a new cycle starts.

Intensive sampling for cycle I began in 1993, and the WMIC was among the first group of study units. Cycle II began its planning phase in 2001, and the WMIC study unit completed intensive sampling during 2002-2004. Low-level sampling is in progress at a limited number of sites in WMIC while our efforts are focused on data analysis and report writing.

CYCLE I

Cycle I of the NAWQA program (1992-2001) focused on status, or assessments of water-quality at 51 major river basins across the country. In the WMIC, water-quality assessments occurred at 11 fixed sites located throughout the study unit. These assessments characterize the ambient water resource for more than 60% of the Nation's drinking water and water for irrigation and industry. One goal of the NAWQA program is to develop a long-term consistent and comparable data set on streams and aquatic ecosystems to support sound management and policy decisions. To meet this goal, each NAWQA study adheres to a nationally consistent study design and methods of sampling and analysis. To learn more about the background of the NAWQA program, please visit the following website: http://water.usgs.gov/nawqa/xrel.pdf. For water-quality data, see our Data page.

CYCLE II

During Cycle II (2002-2012), NAWQA plans to reassess 42 of the original 51 study units. These assessments will fill critical data gaps in the characterization of water-quality conditions; determine trends on a regional level through the Major River Basin (MRB) approach; and build on earlier assessments that link water-quality conditions and trends to anthropogenic and non-anthropogenic factors. Surface water-quality assessment for the WMIC occurred at 4 sites from 2002 through 2004 and at one site (the Popple River) from 2005 through 2006. Beginning in 2007, the surface-water and ecological sampling design for the WMIC was again revised to incorporate intermittent and rotational data collection at 3 sites (Popple River, Duck Creek and Lincoln Creek). For water-quality data, see our Data page.