Hydrogeological Parameter Estimations for Slug Test in Sloping Confined Aquifer

It is necessary to take into account the dip angle effects on accurate estimation of hydrogeological parameters in the sloping confined aquifer. To explore how the dip angle influences the test response, a new slug test model is developed in this study by using theoretical and filed data analysis. For test well, it is found that when the aquifer hydraulic conductivity is relatively low, a larger dip angle causes a faster recovery of the non-oscillatory test response; when the aquifer hydraulic conductivity is relatively high, a larger dip angle causes an increase of amplitude of the oscillatory test response. The dip angle effect is more pronounced for a larger storage coefficient, being less sensitive to the change of transmissivity. An empirical relationship is developed for the limiting dip angle as a function of the dimensionless storage coefficient. The function can be used to predict whether the estimate of hydrogeological parameters would be influenced by the dip angle. The effect can be neglected if the dip angle is less than the upper limit. However, it cannot be neglected if the dip angle is larger than the upper limit, otherwise, it can result in an overestimate of transmissivity and an underestimate of the storage coefficient.