Physical water scarcity is the situation when there is not enough water to meet all demands, such as those required by an ecosystem to function effectively. Arid regions frequently suffer from physical water scarcity. It also occurs where water seems abundant but where resources are over-committed. This can happen where there is overdevelopment of hydraulic infrastructure, often for irrigation. Symptoms of physical water scarcity include environmental degradation and declining groundwater.
The term was first defined in a wide-ranging 2007 study on the use of water in agriculture over the previous 50 years. The study was undertaken by a broad partnership of practitioners, researchers and policymakers, overseen by the International Water Management Institute in Sri Lanka, with the aim of finding out if the world has sufficient water resources to produce food for future populations. The study found that more than 1.2 billion people live in areas of physical water scarcity.
The term economic water scarcity was used by the study to define situations where demand for water is not satisfied because of a lack of investment in water or a lack of human capacity.