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Variation in Specific Capacity in Fractured Rocks, Pennsylvania
Author(s) -
Knopman Debra S.,
Hollyday E. F.
Publication year - 1993
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1993.tb00837.x
Subject(s) - hydrogeology , lithology , geology , variables , casing , ridge , hydrology (agriculture) , soil science , indicator value , linear regression , regression analysis , yield (engineering) , statistics , mathematics , geotechnical engineering , petroleum engineering , petrology , ecology , paleontology , materials science , metallurgy , biology
Statistical analyses were used to determine the relation of hydrogeologic, well construction, and field measurement factors to the extremely variable yield of wells located in consolidated rocks in the Piedmont, Blue Ridge, and Valley and Ridge provinces of Pennsylvania. Specific capacity values (a total of 4,391) from the U.S. Geological Survey well record file were chosen as a measure of yield. Results underscore the importance in regional analysis of accounting for differences due to variables related to well construction and field measurement of specific capacity before attempting to account for differences due to hydrogeology. The approach taken was to organize a hierarchy of variables that relate to differences in specific capacity. Linear regression using log‐transformed specific capacity as the response variable provided estimates of the extent to which variables account for variation in the specific capacity values. Among the variables available for consideration, casing diameter, primary water use, and duration of discharge during the well production test are most important and can explain 24 percent of the variation observed in the specific capacity data. Lithology alone can account for only about 12 percent of the variation observed in the specific capacity data. However, a classification of rocks based on lithology and also accounting for differences in casing diameter, water use, duration of discharge, topographic setting, well depth, and casing depth can explain about half the variation in specific capacity values.