Comparison of Three Groundwater Modeling Studies

Three groundwater modeling studies of a water rights dispute in the San Juan basin of New Mexico are compared. Although these studies all use the same computer model and rely on the same data base, the conclusions they reach are very different. The discrepancies appear to be due primarily to different interpretations of the pump test data used to estimate aquifer parameters in the vicinity of a proposed well field. Since none of the modeling studies attempts to estimate the effect of ambiguous data interpretations on predicted drawdowns, there is no way to judge the relative value of the conflicting results. Although this outcome is disturbing it is not unusual. The credibility of such modeling studies could be greatly improved if they explicitly addressed the factors that control and limit model accuracy.