Operational efficiency and up-coning problem of scavenger wells in lower Indus Basin of Pakistan

Abstract

Groundwater in lower Indus Basin of Pakistan is available in thin aquifers. Abstraction of fresh groundwater can cause up-coning and ultimately degrade water quality in the freshwater aquifer. Up-coning is the saline water intrusion in the freshwater aquifer. Once quality of freshwater is deteriorated because of up-coning, it is very hard to make it again fit for irrigation usage. Thus, it is always advised to abstract groundwater on sustainable level without affecting freshwater aquifer permanently. In this study, we have investigated the operational efficiency of 79 scavenger wells installed at right side of Jamrao canal, lower Indus Basin, Pakistan to check whether these wells were performing with the design operational efficiency. We found that majority of scavenger wells were running quite below the design operational efficiency. The combined operational efficiency of freshwater and saline pumps was 34.3%. The operational efficiency of saline water pumps was slightly higher (37.7%) than the freshwater water pumps (30.7%). We also performed a constant rate pumping test on one of the scavenger wells (i.e. JRS-36) to check whether any chances of up-coning were happening if the both pumps (freshwater and saline water) of the selected scavenger well were operational. The pumping test revealed that chances of up-coning were negligible if the pumps were run within the design operational hours (14.4 h per day).