HYDROLOGIC EVALUATION OF MONTHLY AND ANNUAL GROUNDWATER RECHARGE DYNAMICS FOR A SUSTAINABLE GROUNDWATER RESOURCES MANAGEMENT IN QUETTA CITY, PAKISTAN

Quetta is an important urban center and administrative capital of the Balochistan province of Pakistan. Due to its arid climate and absence of reliable surface water resources, the city heavily relies on groundwater, where rainfall is a prominent source of recharge. As per the past studies, due to increased population and unregulated extraction, groundwater levels in Quetta are declining at a rate of 1.5−5.0 m/year, which calls for a detailed assessment of recharge regime for a sustainable resource protection. Therefore, the monthly and annual groundwater recharge in Quetta from rainfall was computed in this research using the Water Balance Approach for the period 1990−2023. The analysis showed a significant reliance of groundwater recharge on the climate patterns, with the highest monthly recharge in January (21.6 mm) due to high rainfall and low ET, while lowest recharge was found in July (3.31 mm) due to low rainfall and high ET losses, with the mean annual total recharge as 108.6 mm. Further, the Recharge to Precipitation ratio estimated from the daily water balance showed that 15% of annual rainfall contributes to groundwater recharge in Quetta. By evaluating the daily water balance, the study comprehensively explained the monthly and annual groundwater recharge regime, along with the rainfall and ET patterns in Quetta. The outcomes of this research would essentially serve to formulate an effective policy and strategy to optimize the groundwater extraction in Quetta without encroaching the aquifer’s safe yield and to sustainably manage the available groundwater resources for the coming years.