Probability of Unmixed Young Groundwater (defined using chlorofluorocarbon-11 concentrations and tritium activities) in the Eagle River Watershed Valley-Fill Aquifer, Eagle County, North-Central Colorado, 2006-2007
Description
This raster data set delineates the predicted probability of unmixed young groundwater
(defined using chlorofluorocarbon-11 concentrations and tritium activities) in groundwater
in the Eagle River watershed valley-fill aquifer, Eagle County, North-Central Colorado,
2006-2007. This data set was developed by a cooperative project between the U.S.
Geological Survey, Eagle County, the Eagle River Water and Sanitation District, the
Town of Eagle, the Town of Gypsum, and the Upper Eagle Regional Water Authority.
This project was designed to evaluate potential land-development effects on groundwater
and surface-water resources so that informed land-use and water management decisions
can be made. This groundwater probability map and its associated probability maps
were developed as follows: (1) A point data set of wells with groundwater quality and
groundwater age data was overlaid with thematic layers of anthropogenic (related to
human activities) and hydrogeologic data by using a geographic information system
to assign each well values for depth to groundwater, distance to major streams and
canals, distance to gypsum beds, precipitation, soils, and well depth. These data
then were downloaded to a statistical software package for analysis by logistic
regression. (2) Statistical models predicting the probability of elevated nitrate
concentrations, the probability of unmixed young water (using chlorofluorocarbon-11
concentrations and tritium activities), and the probability of elevated volatile organic
compound concentrations were developed using logistic regression techniques.
(3) The statistical models were entered into a GIS and the probability map was
constructed.