Water scarcity exists where the demand for water exceeds supply and where available water resources are approaching or have exceeded sustainable limits. Water scarcity can either be physical or economic.
Physical water scarcity
Occurs where water resources are overexploited for different uses and no longer meet the needs of the population.
Economic water scarcity
Where poor governance, limited capacity, infrastructure and limited investments are among the drivers of economic water scarcity. This type of water scarcity may occur in countries with adequate water resources.
Water stress is an outcome of water scarcity and refers to scarcity in terms of quality and accessibility. Water stress may manifest in conflict over water resources, over-extraction, or poor health and disease.
Extreme water scarcity
Occurs where annual water supply availability is less than 500 cubic metres per person per year. However, this metric has been developed as a global average, applied in varying contexts and includes different uses of water, not only domestic.
The capacity of a population to safeguard sustainable access to adequate quantities of and acceptable quality water for sustaining livelihoods, human well-being, and socioeconomic development, for ensuring protection
against waterborne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability. Water insecurity occurs when any or all of these needs cannot be met.
Extreme water vulnerability
Extreme Water Vulnerability is the combination of the highest levels of physical water scarcity risks and lowest levels of drinking water service that affects a given population (surface water, unimproved or limited water service).