Not All Water is Renewable: A Groundwater Expert Explains

It's a commonly held belief that water is a renewable resource, but that doesn't hold true for groundwater, which is a depletable resource, much like minerals or fossil fuels. Hi, I am Hassan Niazi, working as a researcher at the Joint Global Change Research Institute. There are vast stores of water beneath Earth's surface, but the cost of extracting it climbs as water tables fall lower. When an aquifer’s level falls so low that its water can no longer be reached, or the energy needed to do so grows too costly, extraction becomes infeasible. We need to understand when this depletable resource will peak and decline because groundwater is tied to so many essential functions of society. For example, about a fifth of world’s food is grown using groundwater. My team and I examined 235 water basins around the world. We considered the many factors that could drive basins to depletion across a range of plausible futures. We found that groundwater withdrawals peak globally around mid-21st century, roughly between 2040 and 2060, followed by a decline through the end of the 21st century. Groundwater’s peak and decline pattern is comparable to most depletable natural resources, including gold, copper, etc., which further emphasizes groundwater’s depletable nature. We observed this peak and decline phenomena across 98% of scenarios, so almost all scenarios, making this finding robust across a wide range of plausible futures. Regionally, peak and decline occurs in about one third of the 235 basins, including 21 basins that may have already peaked. This exposes about half of the global population to groundwater stress. The areas of the world that are on track to deplete in the coming decades include Western United States, Mexico, India, Pakistan, China, and several countries in the Middle East and Mediterranean. So, what happens when a region's groundwater peaks? Food prices could rise, aquatic systems could face greater stress, water contamination could spread, and the land above diminished aquifers could sink into the earth more often. We call this phenomenon “land subsidence.” Climbing costs in food production could also spark shifts in international trade as nations seek to import crops or water from less expensive regions. Moving forward, at the very least, affected regions could face the need to adapt their water use and management. This is the most extensive large ensemble experiment done on groundwater to date. It is important to use these findings to shift our perceptions about the depletable nature of groundwater and plan for the future accordingly.