Broadly speaking, water scarcity refers to a mismatch of supply and demand, in which there isn’t enough water to do everything that we want to do. Scarcity – which can be chronic or episodic, local or regional – is generally driven by some combination of rising demand (e.g., due to population growth) and decreasing supply (e.g., due to drought or climate change).

Solutions to scarcity can be grouped into demand-side solutions – water conservation, shifting to less water-intensive crops or industries – and supply-side solutions, such as desalination or wastewater recycling.