Water scarcity

Water scarcity (closely related to water stress or water crisis) is the lack of any, local or economically viably transportable, sources of fresh water resources to meet the standard water demand in a region. There are two types of water scarcity. One is physical. The other is economic water scarcity. Physical water scarcity is where there is not enough water to meet all demands. This includes water needed for ecosystems to function. Regions with a desert climate often face physical water scarcity. Central Asia, West Asia, North Africa, and most of Australia are examples of arid areas. Economic water scarcity results from a lack of investment in infrastructure or technology to draw usable water from rivers, aquifers, and other water sources. It also results from weak human capacity to meet water demand. Many people in sub-Saharan Africa are living with economic water scarcity. There is and has always been enough physical supply of freshwater for current or near or distant future demand in a global scale. As such, water scarcity is caused by a mismatch between when and where people need water, and when and where it is available. This can happen due to an increase in the number of people in a region, changing living conditions and diets, and expansion of irrigated agriculture. Climate change (including droughts or floods), deforestation, water pollution and wasteful use of water can also mean there is not enough water. These variations in scarcity may also be a function of prevailing economic policy and planning approaches. Water scarcity assessments look at many types of information. They include green water (soil moisture), water quality, environmental flow requirements, and virtual water trade. Water stress is one parameter to measure water scarcity. It is useful in the context of Sustainable Development Goal 6. Half a billion people...