EFFECT OF OVEREXPLOITATION OF GROUND WATER RESOURCES ON WATER BALANCE AND QUALITY IN LACHI VALLEY OF DISTRICT KOHAT

摘要

Study was undertaken to evaluate overexploitation of ground water resources in Lachi valley and its effects on ground water balance and quality during the year 2001-2002. Climate of the study area is semi-arid, which necessitates artificial irrigationto undertake agricultural pursuits As no proper surface water exists, the only option remains is to use ground water for irrigation and domestic purposes. In the past few years, low precipitation and reduction in up-stream flow caused the water table todrop at rate of 0.06 to 1.6m per year with average of 0.6m/year. The total recharge to the area amount to 0.550 cumecs, out of which 0.055 cumecs comes from Lachi-Toi and the remaining from precipitation. The total discharge from the area amounts to 0.796 cumecs out of which 0.740 cumecs were discharged by wells and the remaining by natural springs. The discharge from the area is two-third times more than the recharge to the area that imbalanced the aquifer and the ground water quality has deterioratedOut of total thirty-two ground water samples collected randomly from the study area, forty-six percent were found hazardous (mostly in the south-eastern part of the valley, close to the saline water stream), ten percent were marginal (mostly in the north-eastern part of the valley) and forty-four percent were safe (mostly in the western part of the valley).