ABSTRACT
The ability to use geothermal heat requires that it be transferred from the depth to the surface. The most economical and efficient means for doing this relies on naturally occurring, geothermally heated water. If that water is not available in sufficient quantity, technological approaches have been developed for introducing water into the subsurface through engineering efforts. This chapter considers the principles that determine how fluids move through the subsurface, the natural constraints that limit water flow, and the basic principles that apply to enhancing water availability.
