Water shortages, already affecting billions of people around the world, are expected to worsen in the coming decades — linked to drought, pollution, rising sea levels and poor management — but an "invisible" solution may be hiding underground.

With water usage seen rising by 1% each year over the next three decades, a U.N. report predicted on Monday that so-called groundwater will grow in importance as climate change and human exploitation shrink surface supplies like lakes and reservoirs.

Today, groundwater — which accounts for 99% of the planet's freshwater supplies — is poorly understood and consequently undervalued, mismanaged and even abused, according to the U.N. World Water Development Report 2022.