ISSN:
1745-6584
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Geosciences
Notes:
Water-table altitude, a controlling factor for ground- water flow, was estimated from detailed topographic data by subtracting the estimated depth-to-water. Land-surface altitude of the Coastal Plain in the south-central United States varies from 0 to more than 800 feet above sea level. Predevelopment depth-to-water in 6,825 wells less than 150 feet deep averages 25.7 feet (standard deviation, 19.5 feet). Most water-table-altitude variation is due to variation in land-surface altitude and not due to variation in depth-to- water. Digital topographic data, from 1:250,000 scale maps for every 30 seconds of latitude and longitude are available for the continental United States. About 90 altitudes were averaged for each 25-square-mile block of a rectangular grid used for ground-water flow modeling. Multiple linear regressions of predevelopment water-level data and topographic data were used to derive empirical equations relating water-table altitude to topography.The regression method was more consistent, efficient, and accurate than manually digitizing values from manually contoured water-table maps. Water-table maps usually are prepared from few data that are concentrated in topographically flat areas. Manually digitizing water-table maps on a regional scale introduces additional error. About 35 percent of the water-table altitudes obtained manually were greater than average land-surface altitudes from topographic data. The mean difference between water-table altitudes from the two methods was less than 10 feet, which indicates no systematic error was incorporated in the regression method.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-6584.1989.tb00457.x
Permalink