PNNL

Abstract

Over the past 50 years, humans have extracted the Earth’s groundwater stocks at a steep rate, largely to fuel the irrigated green revolution of global agro-economic development. Given society’s growing reliance on groundwater, we explore ‘peak water limits’ to investigate whether, when, and where humanity might reach peak groundwater extraction. Using an integrated global model of the coupled human-Earth system, we simulate groundwater withdrawals across 235 water basins under 900 future scenarios covering a wide range of human and Earth system dimensions of global change over the 21st century. We find that global nonrenewable groundwater extraction exhibits a distinct peak-and-decline signature, characteristic of most depletable natural resources including oil, gold, copper, etc., in nearly all (98%) of the scenarios, peaking on average at 625 km3yr-1 around mid-century, followed by a consistent decline through 2100. Peak-and-decline occurs in about one-third (82) of basins across all scenarios, with 21 basins that might have already peaked, exposing about half (44%) of the global population to groundwater stress. Most of these basins are in countries with the highest current extraction rates, including the U.S., Mexico, Pakistan, India, China, Saudi Arabia, and Iran. Water basins that are now heavily dependent on groundwater resources for meeting their demands will likely face increasing costs of groundwater and food production, with important implications for global agricultural trade. Groundwater’s role in meeting global water demands will likely diminish toward the end of the century.