Simple Probabilistic and Statistical Risk Calculations in an Aquifer

Abstract

An objective methodology is proposed for assessing potential ground water yield on the basis of the randomness inherent in hydrogeological parameters as a result of uncertainty. Randomness is used here in the statistical sense to describe the ground water phenomenon on a regional basis. A systematic approach to selecting aquifer parameters is presented that leads to reliable ground water storage and subsurface flow estimates by incorporating a certain risk level. In addition, the averages of the specific ground water capacity and subsurface flow rate are calculated through a perturbation approach. This study demonstrates that cross-correlations between basic hydrogeologic variables might underestimate or overestimate model parameter values. Furthermore, the results of aquifer storage and subsurface flow estimates are obtained in the form of probability distribution functions. It is proved that the surface flow rates are presented by a log-normal distribution. Contrary to conventional point estimate, a simple and objective methodology is proposed in order to obtain the most probable interval estimates. Accordingly, projections of likely future ground water storage and flow rates can be readily calculated.