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.
The RASA Program represents a systematic effort to study a number of the Nation's most important aquifer systems, which, in aggregate, underlie much of the country and which represent an important component of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and, accordingly, transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies to develop an understanding of the natural, undisturbed hydrologic system and the changes brought about in it by human activities and to provide a means of predicting the regional effects of future pumping or other stresses. The final interpretive results of the RASA Program are presented in a series of U.S. Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of each regional aquifer system. Each study within the RASA Program is assigned a single Professional Paper number beginning with Professional Paper 1400.
The Regional Aquifer-System Analysis Program The RASA Program represents a systematic effort to study a number of the Nation's most important aquifer systems, which, in aggregate, underlie much of the country and which represent an important component of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and, accordingly, transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies to develop an understanding of the natural, undisturbed hydrologic system and the changes brought about in it by human activities and to provide a means of predicting the regional effects of future pumping or other stresses. The final interpretive results of the RASA Program are presented in a series of U.S.
The method of identifying dry stream reaches in carbonate terrane as surface indicators of potential ground‐water reservoirs offers a valuable exploration technique that is more rapid and less expensive than traditional exploration methods involving random test drilling. In areas where dry stream reaches occur, subsurface drainage successfully competes with surface drainage, and sheet‐like dissolution openings have developed parallel to bedding creating the ground‐water reservoir. The occurrence and hydraulic characteristics of such reservoirs are highly variable, as attested to by the wide range of well yields. Union Hollow in south‐central Tennessee is the setting for a case study that illustrates the application of the dry stream reach technique. In this technique, dry stream reach identification is based on two types of readily acquired information: (1) remotely sensed black and white infrared aerial photography; and (2) surface reconnaissance of stream channel characteristics. Test drilling in Union Hollow subsequent to identification of the dry reach proved that a localized ground‐water reservoir was present.
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