Delineation of Wellhead Protection Areas: Theory and Practice

Abstract

A preventive approach in groundwater protection programs throughout Europe and the United States, and almost unknown in Brazil, is to define the surface and subsurface areas, the Wellhead Protection Area (WHPA), from which a well or wellfield draws its water during a specified time. Overlaying a map of potential pollution sources on the delineated WHPA (Figure 1), those sources which fall within the WHPA boundaries are identified as definite threats, that need to be closely monitored, to the continued safe operation of the wellfield. Given the importance of effectively delineating the WHPA to protect public water supplies, the current delineation criteria, methods, and zones are presented, as well as analytical and numerical PC model analyses of different hydrogeological scenarios' effects on WHPA's size, shape and direction. Numerical models are shown to more accurately define WHPAs by taking into account the surrounding heterogeneous and anisotropic geology.