Monitoring changes in well performance over time provides the data needed by managers to determine the need for well rehabilitation or replacement. Long term aquifer tests are used to determine aquifer characteristics. These data are used to plan well field expansions, estimate well interference and delineate well head protection areas. Modeling is one of the peripheral aspects that is most abused by nonhydrogeologists performing hydrogeologic services . The modeling approach chosen has to be appropriate for the hydrogeology of the location .
Different models are capable of different kinds of simulations, and some are better than others.
Usually, the WHPA is based on the amount of time a contaminant may take to travel through the area to reach the water source, often 1 and 5 years, as specified in Ohio by the Ohio EPA . Within the WHPA, potential sources of contaminants are identified and managed to prevent contamination. Hydrogeologic analysis can determine whether a potential threat is likely to be real or not. Monitoring of ground water quality in the vicinity of the WHPA is regularly conducted to determine if a contaminant is migrating toward the water supply from an unknown source. Neither extreme is recommended, of course.