Responses of Groundwater Lowering Systems: Empirical Equations Via Field Records

Abstract

This study aims to evaluate the accuracy of analytical equations which are mostly used in the design of dewatering systems using deepwells. This is accomplished by analyzing the data obtained from dewatering systems executed in twenty different sites within the Egyptian Nile Valley and Delta. The studied cases included gravity flow (unconfined aquifer), artesian flow (confined aquifer) and mixed flow (semi-confined aquifer) cases. For each of the considered sites, the actual discharge from pumping drilled wells and the actual drawdown of the groundwater table were measured. Besides, a pumping test was performed at each of these sites. The field data was then analyzed by adopting the empirical analytical equations to assess the responses of groundwater to the implemented lowering systems. The obtained results showed that the actual monitored drawdown values were not in good agreement with the analytical results. Therefore, practical correlation factors, based on data from the investigated sites and a comprehensive parametric study, were derived to enhance the results of the analytical equations. Hence, by implementing such cumulative drawdown correlation factors in the empirical equations, a more accurate assessment of the expected drawdown values can be attained. For aquifers within the Nile valley and Delta, average cumulative drawdown correlation factors of 0.7, 0.65 and 0.8 were found to be satisfactory for unconfined aquifers, confined aquifers, and semi-confined aquifers, respectively.