Boundary of the Eagle River Watershed Valley-Fill Aquifer, Eagle County, North-Central Colorado, 2006-2007

This vector data set delineates the approximate boundary of the Eagle River watershed valley-fill aquifer (ERWVFA).
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. The boundary of the ERWVFA
was developed by combining information from two data sources. The first data source was a 1:250,000-scale geologic
map of the Leadville quadrangle developed by Day and others (1999). The location of Quaternary sediments was used
as a first approximation of the ERWVFA. The boundary of the ERWVFA was further refined by overlaying the geologic
map with Digital Raster Graphic (DRG) scanned images of 1:24,000 topographic maps (U.S. Geological Survey, 2001).
Where appropriate, the boundary of the ERWVFA was remapped to correspond with the edge of the valley-fill aquifer
marked by an abrupt change in topography at the edge of the valley floor throughout the Eagle River watershed. The
boundary of the ERWVFA more closely resembles a hydrogeomorphic region presented by Rupert (2003, p. 8) because
it is based upon general geographic extents of geologic materials and not on an actual aquifer location as would be
determined through a rigorous hydrogeologic investigation.