Freshwater aquifers are one of our main sources of water. Aquifers are layers of rock that bear water underground, and fill up from rainwater and melting snow. Aquifers can flow out in streams, but more frequently have wells drilled into them to pull the water for drinking, as well as industrial and agricultural uses. Aquifers can dry up if we drain them faster than they are refilled.
Many major aquifers around the world are exploited unsustainably, even to the point of approaching environmentally unsafe drawdown limits in this century. Aquifer depletion tends to happen in regions that are important to crop production, so dried up aquifers pose a global food security threat.
STREAMer Sean Turner used the Global Change Assessment Model (GCAM) to investigate the response to severe constraints on global water resources, focusing on the land use and agriculture sectors. A scenario was created where many important aquifers became so depleted that further withdrawal was not possible. The results from that model were compared to a control model that had no constraints on water withdrawals.
The results of this study show that groundwater depletion and the associated increase in water price increased two distinct responses from the agriculture sector: there was an expansion in rain fed agriculture, and irrigated crop production shifted towards regions with cheaper water resources. Water stressed regions with groundwater being depleted unsustainably were most affected by losses in crop production. Specifically, these places were northwest India, Pakistan, the Middle East, western United States, Mexico, and central Asia.
These results highlighted substantial risks for the affected regional agricultural economies. However, the model also showed that modest changes in irrigation and location of crop growth could meet global food demands despite severe water constraints. Whilst this study simulated a world with frictionless trade, these ideas are important as world leaders must take water constraints into consideration, given how affected everyone will be if we deplete these natural resources.
Full article: A pathway of global food supply adaptation in a world with increasingly constrained groundwater, Sean WD Turner, Mohamad Hejazi, Katherine Calvin, Page Kyle, Sonny Kim, Science of the Total Environment
