Well selection, Maha Abstract

U.S. Geological Survey

Well selection for assessing ground-water quality in carbonate valleys in the Valley and Ridge province of Pennsylvania, Lower Susquehanna River Basin study unit, National Water-Quality Assessment program

Bruce D. Lindsey and Steven F. Siwiec
Two primary objectives of the ground-water component of the National Water-Quality Assessment (NAWQA) program are to (1) provide a description of current water-quality conditions, and (2) explain the major factors that affect water quality. This presentation describes the selection of a set of existing wells from which samples are to be collected to describe and explain the quality of ground water used for rural domestic purposes in agricultural areas underlain by Cambrian and Ordovician carbonate bedrock in the Valley and Ridge physiographic province in the Lower Susquehanna River Basin. The selection process uses a Geographic Information System (GIS) to assimilate and display information about the major factors that affect water quality. Physiographic, geologic, and land-use data layers or coverages are spatially overlain to delineate the area for study. A GIS-based site-selection algorithm is then used to subdivide the study area into 30 equal-area cells and to locate candidate sampling locations. Thirty sampling sites are necessary for the interpretation of water-quality data by use of statistical analyses. The algorithm randomly identifies one primary and two alternative locations in each cell. The locations are used as starting points to locate existing domestic wells suitable for sampling. From these starting points, wells are selected that meet an established set of well-site evaluation criteria, which include field verification of current land use, site history, well-construction factors, and sampling considerations.

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