Raster dataset showing the probability of detecting atrazine/desethyl-atrazine in ground water in Colorado, hydrogeomorphic regions included and atrazine use estimates not included.

This dataset is one of eight datasets produced by this study. Four of the 
datasets predict the probability of detecting atrazine and(or) desethyl-atrazine 
(a breakdown product of atrazine) in ground water in Colorado; the other four 
predict the probability of detecting elevated concentrations of nitrate in ground 
water in Colorado. The four datasets that predict the probability of atrazine 
and (or) desethyl-atrazine (atrazine/DEA) are differentiated by whether or not 
they incorporated atrazine use and whether or not they incorporated 
hydrogeomorphic regions. The four datasets that predict the probability of 
elevated concentrations of nitrate are differentiated by whether or not they 
incorporated fertilizer use and whether or not they incorporated hydrogeomorphic 
regions. Each of the eight datasets has its own unique strengths and weaknesses. 
The user is cautioned to read Rupert (2003, Probability of detecting 
atrazine/desethyl-atrazine and elevated concentrations of nitrate in ground 
water in Colorado: U.S. Geological Survey Water-Resources Investigations 
Report 02-4269, 35 p., http://water.usgs.gov/pubs/wri/wri02-4269/) to determine 
if he(she) is using the most appropriate dataset for his(her) particular needs. 
			
This dataset specifically predicts the probability of detecting atrazine/DEA in 
ground water in Colorado with hydrogeomorphic regions included and atrazine 
use estimates not included. 
			
The following text was extracted from Rupert (2003). 
			
Draft Federal regulations may require that each State develop a State Pesticide 
Management Plan for the herbicides atrazine, alachlor, metolachlor, and simazine. 
Maps were developed that the State of Colorado could use to predict the probability 
of detecting atrazine/DEA in ground water in Colorado. These maps can be incorporated 
into the State Pesticide Management Plan and can help provide a sound hydrogeologic 
basis for atrazine management in Colorado. Maps showing the probability of detecting 
elevated nitrite plus nitrate as nitrogen (nitrate) concentrations in ground water in Colorado 
also were developed because nitrate is a contaminant of concern in many areas of Colorado.
			
Maps showing the probability of detecting atrazine/DEA at or greater than concentrations 
of 0.1 microgram per liter and nitrate concentrations in ground water greater than 5 milligrams 
per liter were developed as follows: 
			
(1) Ground-water quality data were overlaid with anthropogenic and hydrogeologic data by 
using a geographic information system (GIS) to produce a dataset in which each well had 
corresponding data on atrazine use, fertilizer use, geology, hydrogeomorphic regions, 
land cover, precipitation, soils, and well construction. These data then were downloaded 
to a statistical software package for analysis by logistic regression. 
			
(2) Relations were observed between ground-water quality and the percentage of land-cover 
categories within circular regions (buffers) around wells. Several buffer sizes were evaluated; 
the buffer size that provided the strongest relation was selected for use in the logistic 
regression models. 
			
(3) Relations between concentrations of atrazine/DEA and nitrate in ground water and 
atrazine use, fertilizer use, geology, hydrogeomorphic regions, land cover, precipitation, 
soils, and well-construction data were evaluated, and several preliminary multivariate 
models with various combinations of independent variables were constructed. 
			
(4) The multivariate models that best predicted the presence of atrazine/DEA and 
elevated concentrations of nitrate in ground water were selected. 
			
(5) The accuracy of the multivariate models was confirmed by validating the models 
with an independent set of ground-water quality data. 
			
(6) The multivariate models were entered into a geographic information system 
and the probability GRIDS were constructed.

Tags: atrazine, desethyl-atrazine, environment, geoscientificinformation, ground-water, ground-water-contamination, ground-water-probability, ground-water-quality, ground-water-susceptibility, ground-water-vulnerability, inlandwaters, nitrate, probability, probability-of-ground-water-contamination, susceptibility, usgs-eeee80c5-1a83-488b-9a82-736373d962c6, vulnerability
Organization: Department of the Interior