Oil and gas have long dominated strategic thinking, but water is emerging as an equally important resource in many regions.
Population growth, climate change and rising demand are increasing pressure on rivers, aquifers and reservoirs.
Where water systems cross borders, scarcity can create diplomatic tension. Upstream dams, changing rainfall and competing agricultural needs may affect multiple countries at once.
At the same time, water insecurity can drive migration, reduce food production and weaken economic stability.
Regions in parts of Africa, South Asia and the Middle East are often cited as particularly exposed, though the challenge is global.
Yet water does not have to be a source of conflict. Shared river basins can also encourage cooperation, data sharing and joint infrastructure planning.
Experts say the future significance of water lies in this dual role: it can deepen rivalry or create incentives for collaboration.
In that sense, water security may become one of the defining tests of international governance in the decades ahead.
