The effects of aquifer and well parameters on Capture Zone and Discharge Zone in alluvial unconfined aquifers

In order to protect water wells, it is necessary to analyze the zones of influence, capture, recharge and discharge zones. Despite much research, this issue still needs further discussion. The purpose of this research is to analyze the capture and discharge zones of water wells in alluvial unconfined aquifers. For this purpose, a hypothetical aquifer was simulated using the Modflow and Modpath models. The accuracy of the numerical model outputs was confirmed by comparison with the analytical calculations, and then the effect of the independent parameters of the well and the aquifer was investigated. This research showed that, contrary to popular belief, changes in hydraulic conductivity, specific yield, bedrock dip, initial thickness, porosity, and heterogeneity do not cause changes in the surface extent of the well's capture zone in the unconfined aquifer.This research has shown that changes in surface recharge, discharge and well location cause many changes in the surface extent of the well capture zone in unconfined alluvial aquifers. Investigation of the effect of pumping time in a single well system showed that the size of the capture zone initially increases, but after a short period, of time, despite the continued expansion of the drawdown cone, its position stabilises. It was found that the change in all the above parameters causes a change in the size of the well's discharge zone. The stability of the above-mentioned areas is very important for the determination of zones for the protection of the quantity and quality of water wells! It has been found that the relative stability of the water level in the aquifer at an appropriate level is necessary, and this requires the management of the aquifer and the allocation of a limited percentage of the aquifer recharge to discharge through wells.