Ground water exploration and development in igneous and metamorphic rocks of the southern Piedmont/Blue Ridge
Crawford, Thomas J.
Kath, Randy L.
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Concepts of ground water movement in igneous and metamorphic rocks in areas with a subtropical climate, such as that of the southeastern United States, have evolved over many decades. However, because of the dearth of research directed toward an understanding of the variables involved, much of the data set concerning the hydrogeology of igneous and metamorphic rocks is empirical data generated by ground water exploration and development. Some of the concepts derived from these empirical observations and from limited applied research, have been presented and discussed in various papers dealing with the hydrogeology of igneous and metamorphic rocks in the southern Piedmont/Blue Ridge. Igneous and metamorphic rocks have, in many places, very diverse properties that change over short distances both vertically and horizontally. Our experience over the last 35 years indicates that, because of this, ground water movement is often most influenced by the relative properties of various rock units or discontinuities rather than by absolute properties of a particular rock unit or discontinuity. This relationship greatly complicates attempts to understand the hydrogeology of igneous and metamorphic rocks-, and emphasizes the need for a strong and broad data base where it is desirable to make predictions concerning ground water. This paper discusses some of the major controls of ground water occurrences in igneous and metamorphic rocks. Determining and evaluating these controls on a site-specific basis greatly enhances the probability of successful ground water exploration, development and management.