National Water-Quality Assessment (NAWQA) Program
Groundwater-flow modeling and geochemistry are being used by NAWQA to quantify the factors leading to observed groundwater-quality trends, and to project future trends of groundwater quality on the basis of various contaminant-input scenarios. This is an important component of groundwater-quality investigations because it accounts for the complex interaction of geology, hydrology, and chemistry, and because it provides a scientifically-based way to extrapolate current understanding into the future.
For example, naturally occurring microbial processes (biotransformation) can transform trichloroethene over time in groundwater systems (Chapelle and others, 2012). The rates at which these processes occur will ultimately determine how long it will take for the contamination to naturally disperse in a fractured-rock aquifer.
A simulation and forecasting study was completed by Kauffman and others (2001) in a 400 square-mile study area near Glassboro, New Jersey. They used a three-dimensional steady-state groundwater-flow model in conjunction with particle tracking to examine the effects of land use and travel time on the distribution of nitrate in groundwater and surface water in southern New Jersey.