The changing characteristics of groundwater sustainability in Pakistan from 2002 to 2016

Groundwater is regarded as one of the most reliable and vulnerable sources of drinking water in many countries. Declining groundwater levels, due to over-exploitation and climate-change impacts, emphasize the need for sustainable management of this valuable resource. The concept of reliability-resiliency-vulnerability (RRV) has been adopted in this study to assess the spatial changes in the sustainability of aquifers for different periods to identify the main factors affecting groundwater sustainability in Pakistan. This is important for the country, as the substantial decline of groundwater levels in recent years has affected the water security of the growing economy. The satellite-based gridded Gravity Recovery and Climate Experiment (GRACE) groundwater anomaly data for the period 2002-2016 were used for this spatial assessment. The results revealed precipitation as the dominant factor associated with changing groundwater storage in Pakistan. A large decrease in aquifer storage was found over the study period. The groundwater-level decline was found to be greater in the region where agriculture is more intense, resulting in over-exploitation of groundwater for irrigation. The reduction of groundwater storage has led to a decrease in sustainability, especially in recent years (2008-2016) compared with previous periods (2002-2010 and 2005-2013). This study emphasized the need for groundwater resource management strategies such as reduction of groundwater abstraction in drought years, rescheduling the crop calendar to take advantage of rainfall, switching to less water-intensive crops, etc., particularly in groundwater depleting regions.