Groundwater Depletion and water competition in transboundary aquifers

Transboundary aquifers (TBAs) are crucial for global food production, supporting about a quarter of the world’s irrigated cropland. However, they remain inadequately regulated, with fewer than 10 international treaties addressing shared groundwater. This lack of regulation raises concerns about potential international tensions stemming from water competition and the premature depletion of these vital resources.

Analyzing data from 170,000 wells, we found that while TBAs are not significantly more overexploited than non-transboundary aquifers, wells located near international borders exhibit higher depletion rates. This pattern aligns with increased competition driven by transboundary interactions. New spatial data on irrigated cropland reveals that competition is concentrated in about half of the country pairs sharing an aquifer, where irrigated cropland is situated close enough to borders to cause cross-border groundwater drawdown. In most of these cases, the TBA extent is small and contributes only a minor portion of national irrigation, which raises the potential for negotiated management. However, about 20% of the cases represent high-priority hotspots due to strong transboundary interactions and the strategic importance of the aquifer, which overlays a substantial portion of both countries’ irrigated cropland. Implementing zone-based pumping restrictions could alleviate competitive pressures in these areas, making them key targets to consider for ongoing efforts to support transboundary groundwater cooperation.