Prospect Risk Analysis Applied to Ground‐Water Reservoir Evaluation

A methodology is proposed which provides predevelopment assessments of the potential yield of ground-water reservoirs. A systematic assessment of aquifer parameters leads to estimates of ground-water storage capacity and the geologic risks that may affect those estimates. Area of reservoir, average saturated thickness of aquifers to a limit of economic dewatering, and average specific yield, all arrived at through a Delphi procedure are combined in a Monte Carlo simulation to yield an unrisked product at several probability levels. Marginal probabilities are assigned to each parameter and combined in a further Monte Carlo simulation to yield a series of risked estimates. The results are expressed in a table and as cumulative probability curves of ground-water storage capacity that can provide a basis for economic modeling. The method is analogous to methods widely applied in the petroleum and other extractive industries. All basic hydrogeologic data are laid out in a systematic way, permitting planners to compare reservoirs on a common basis and to judge the reliability of the estimates. Once the geologic models have been developed, they can be updated readily as additional information becomes available. The method is particularly well-suited to preliminary assessments of the development potential of undeveloped or poorly-explored areas, and to regional evalution where only parts of the regional have been subject to intensive ground-water development.