WWRC 96-07
Determination of Nonpoint-Source Pollution Using GIS and Numerical Models
Abstract
A geographic information system (GIS) was utilized to apply a
modified DRASTIC method to the assessment of groundwater contamination
sensitivity in Goshen County, Wyoming. Several basic environmental
characteristics, identified as influencing contaminant transport
through the vadose zone to groundwater systems, were mapped, automated,
and analyzed. These characteristics include: depth to groundwater,
net recharge, hydrogeologic setting, vadose zone soil properties,
land surface slope, and saturated hydraulic conductivity. Sensitivity
ratings were developed for each parameter based on a combination
of mathematical functions and the inherent capacity of each characteristic
to influence transport of contaminants. A raster-based overlay
analysis was performed to derive a map that portrays cumulative
aquifer sensitivity ratings across the county, providing a relative indication
of groundwater vulnerability to contamination. A process-based
numerical model was used to simulate water flow and solute transport
in the vadose zone and groundwater systems. The model incorporated
soil and hydraulic properties produced with the GIS into the simulations.
Numerical simulations described the time and spatial distributions
of contaminants. Chemical mass stored in the soil and leaching
out from the vadose zone were computed to characterize groundwater
contamination. Groundwater sensitivity indexes, which were developed
based on the numerical modeling results, were compared with the
GIS sensitivity map and used to verify the reliability of the map.
Water Resources Publications List
Water Resources Data System Library |
Water Resources Data System Homepage
