RedN NAWQA
USGS IN YOUR STATE
USGS Water Science Centers are located in each state.
|
Red River of the North Basin
National Water-Quality Assessment Program
Stoner, J.D., Stark, J.R., and Hines, J.W., 1996, Technical considerations for
monitoring ground water to assess water- quality trends in Minnesota:
Minnesota Water `96 collection of conference abstracts, May 20-21, 1996,
Minneapolis, Minnesota, University of Minnesota Water Resources Research
Center, p. 36.
Abstract
The Interagency Ground Water Monitoring Coordination Group, comprised of
water-monitoring specialists from State and Federal agencies, recognized that
clearly defined and achievable objectives are essential before considering technical
factors in a Minnesota or regional ground-water monitoring program. For example,
the basic question, "Is the quality of ground water in an aquifer degrading over
time?" logically could raise new questions about hydrogeologic characteristics,
pollution source(s), water use, and historical water-quality data. Subsequently1,
answers to these questions are needed to establish components of monitoring design
and assessment, such as well-construction criteria, location, sampling protocols,
frequency and duration of sampling, constituents of importance, and methods of
data analysis.
Reviews of water-quality data have identified some of the pitfalls of extending data
interpretations to evaluate trends using data that were collected for other purposes.
For example, data reviews by the U.S. Geological Survey, Minnesota Pollution
Control Agency, and the Minnesota Department of Agriculture have shown apparent
increasing trends in nitrate concentrations over time in Minnesota ground water.
However, samples to date are not sufficient to quantify trends in space or time.
Surficial aquifers in Minnesota are among the most susceptible to contamination
from land-surface activities such as urbanization, agriculture, or accidental spills.
An early warning approach to ground-water monitoring may be desirable for these
surficial aquifers to identify causes of water-quality degradation and to effect
remediation before contamination spreads. Recent research tools, such as age dating
of ground water using chloroflourocarbons, have shown that ground-water residence
time can vary from a few years to decades within a vertical distance of 30 feet in
some surficial sand and gravel aquifers. Sampling of shallow wells, which are
completed near the water table of surficial aquifers, could be important as an early
warning method. Unfortunately, existing water wells rarely meet this criterion.
Ground-water monitoring can be costly, but technically valid implementation of
monitoring to achieve early warning objectives can promote wise water management
and reduce costs of remediation.
|
U.S. Department of the Interior |
U.S. Geological Survey