Causes and effects of temporal groundwater level change in the alluvial aquifer of Dera Ismail Khan area, Pakistan

Abstract

The Chashma Right Bank Canal (CRBC) Stage-II Command Area lies in the Dera Ismail Khan District of Lower Indus Basin. The Indus River and tube wells were used in the past for irrigation purpose, which are now changed to the canal irrigation system. In this research the pre and post water table depths have been investigated to assess the vulnerability of the irrigated land due to water logging. To address this problem the subsurface area has been explored using the water table depth in integration with depositional unit correlation, lateral zonation of hydraulic conductivity and recharge difference calculation for 1976 and 1996. The recharge determined in 1976 using the Water Table Fluctuation (WTF) method is 6 cm. The recharge in 1996 is greater than that of 1976. The groundwater recharge difference between 1976 and 1996 is determined to be 0.64 m. Moreover, three distinct zones have been found which divide the unconfined aquifer vertically into fine to medium sand, medium to coarse sand with gravels and the medium sand. Three lateral zones namely A, B and C are identified on the basis of the water level difference and hydraulic conductivity. Zone B which occupies the middle part has been found to be more vulnerable to the water logging conditions as compared to the other two zones. The role of hydraulic conductivity in zone B is found critical in the buildup of higher water table zones leading to the land degradation in response to perched water table zones development.