GEOGRAPHY
A spatial statistical correlation of drainage density and surface water quality degradation in
Kentucky. NICHOLAS R. LAWHON*, Hoffman Environmental Research Institute, Department
of Geography and Geology, Western Kentucky University, Bowling Green, KY, 42101.
rainage density is often overlooked as an influential factor on the water quality research of
surface streams. In order to ascertain what, if any, influence this factor exerts on surface water
quality degradation, Geographic Information Systems (GIS) analysis was used to perform spatial
interpolation and statistical analyses of the drainage density of streams in Kentucky. Kernel
Density Estimations were used to create raster datasets of three different stream flow line files:
the US Geological Survey National Hydrography Dataset (USGS NHD) data for overall drainage
density, a modified file from the NHD administered by the US Environmental Protection Agency
which shows only those streams that are listed as having water quality impairments with respect
to regulations set forth in section 301 of the Clean Water Act (streams in which one or more
regulated parameters violate regulatory standards) , and finally the Kentucky Division of Water’s
“exceptional use water bodies’ shapefile which shows only streams that not only meet but
handily exceed water quality standards. These raster datasets were in turn exposed to
multivariate statistics through the Raster Band collection tool to identify any statistically
significant relationships between the three layers. This process yielded a correlation coefficient
of 0.72022 between overall drainage density and that of streams of impaired water quality,
indicating that there is likely some significant correlation between drainage density and potential
for surface water quality degradation.