Global water resources are facing many challenges from climate extremes, such as floods and droughts, and human water use, particularly irrigation. While many studies emphasize water scarcity, water management in many regions faces challenges from too much vs too little water related to floods and droughts. A variety of approaches are used to assess spatiotemporal variability on global water resources, including satellites, global and regional modeling, and ground-based monitoring.
In this presentation, I will review spatiotemporal variability in global water resources using GRACE satellite data with particular emphasis on groundwater. The satellite data will be compared with modeling and ground-based monitoring data. Emphasis is placed on potential solutions to resolve water-resource issues.
Total water storage trends have varied across regions over the past century. Satellite data from the Gravity Recovery and Climate Experiment (GRACE) show declining, stable and rising trends in total water storage over the past two decades in various regions globally. There is large variability among global models which generally underestimate water storage trends relative to GRACE data. Groundwater monitoring provides longer-term context over the past century, showing rising water storage in northwest India, central Pakistan and the northwest United States, and declining water storage in the US High Plains and Central Valley. Impacts of climate extremes on water storage, particularly droughts, are recorded in many regions and are amplified or dampened by irrigation depending on the water source (surface water/groundwater). Water-resource resilience can be increased by diversifying management strategies, including conjunctive use of surface water and groundwater for irrigation, increasing supplies (desalination, wastewater reuse), reducing withdrawals (conservation), storing water in surface reservoirs and depleted aquifers (managed aquifer recharge), and transporting water. A diverse portfolio of these solutions, in tandem with managing surface water and groundwater as a single resource, can help address human and ecosystem needs while building a resilient water future.