Water scarcity and water insecurity are related concepts but not identical, and each has a range of interpretations leading to some overlap. Water scarcity can be broadly described as a mismatch between the demand for fresh water and its availability, quantified in physical terms. Water security/insecurity is a broader concept with definitions beyond physical water scarcity, encompassing access to water services, safety from poor water quality and flooding, and appropriate water governance that ensures access to safe water . Metrics of water security include both physical and socioeconomic components and are a tool for comparison between different locations and countries regarding relative levels of water security in the context of water-related risks. Some definitions of water scarcity also incorporate these broader issues. For example, 'economic water scarcity' has been defined as a situation where 'human, institutional, and financial capital limit access to water, even though water in nature is available locally to meet human demands' . Economic water scarcity can also occur where infrastructure exists, but water distribution is inequitable . Much of the literature exploring the impacts of climate change on water security, however, focuses on quantifying physical water scarcity. Discussions in this box consider physical water scarcity as a quantifiable measure of water availability compared to its demand and consider the societal elements of economic water scarcity to be part of the more comprehensive concept of water insecurity.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report