Wherever you are in the world, chances are you are sitting on water. Drill down deep enough and you’ll find it. Beneath the Earth’s surface aquifers are natural reservoirs that contain groundwater. Collectively they constitute the largest amount of liquid freshwater on Earth. They are a vital source of drinking water for humans and livestock, and also offer a potential solution to increasing global problems of water scarcity.

Why is groundwater so important? First, it’s generally a more reliable source of water than surface water, which is naturally protected from contamination. Second, groundwater acts as a natural buffer from drought, helping to smooth out rainfall patterns, thereby increasing resilience to climate change. Finally, it can generally be found close to the point of demand.

It’s for these reasons and more that groundwater is the main source of water in low-income countries. Only 2% of the rural population in Southern Asia, 5% of the rural population in Southeastern Asia and 20% of rural dwellers in sub-Saharan Africa rely on surface water sources.