This digital product contains gridded estimates of water-table (wt) elevation and depth to water (dtw) under dry, normal, and wet conditions for Sussex County, Delaware. Files containing the point data used to create the grids are also included. This work is the final component of a larger effort to provide estimates of water-table elevations and depths to water for the Coastal Plain portion of Delaware. Mapping was supported by the Delaware Department of Natural Resources and Environmental Control and the Delaware Geological Survey.
These grids were produced with the same multiple linear regression (MLR) method as Andres and Martin (2005). Briefly, this method consists of: identifying dry, normal, and wet periods from long-term observation well data (Nc45-01, Ng11-01, Qe44-01); estimating a minimum water table (Sepulveda, 2002) by fitting a localized polynomial surface to elevations of surface water features (e.g., streams, swamps, and marshes); and computing a second variable in the regression from water levels observed in wells. A separate MLR equation was determined for dry, normal, and wet periods, and these equations were used in ArcMap v.9 (ESRI, 2004) to estimate grids of water-table elevations and depths to water. Grids produced in this project were merged with those previously completed for eastern Sussex and smoothed to minimize edge effects.
Please Note: Many datasets on this site are available as compressed and zipped 7z files. To "unzip" the 7z file, you must obtain the free and open source 7zip program.
WMS URL: http://maps.dgs.udel.edu/fcgi-bin/de_watertable?
Layer Names: de_dry_dtw, de_norm_dtw, de_wet_dtw, de_dry_wtelev, de_norm_wtelev, de_wet_wtelev
Please give proper credit to the Delaware Geological Survey.
The grids have 30-m horizontal and 1-ft vertical resolutions. In the accompanying digital data, grid world files and ground-water level observation data are in UTM-18N, 1983 projection in meters and elevations are in feet, NAVD 1988. Files are in ESRI, Inc., grid and TIF formats.
Layer Name Definitions:
- de_dry_dtw = Depth to Water Table in a Dry Year
- de_norm_dtw = Depth to Water Table in a Normal Year
- de_wet_dtw = Depth to Water Table in a Wet Year
- de_dry_welevt = Water Table Elevation in a Dry Year
- de_norm_wtelev = Water Table Elevation in a Normal Year
- de_wet_wtelev = Water Table Elevation in a Wet Year