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EQ3: Why is water insecurity becoming such a global issue for the C21st? GapFill
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The distribution of the world’s water is not , meaning that water availability and demand do not always match up.
Areas that are under water stress have less than m3 of water available per person each year. Areas of water scarcity have less than m3 of water available per person each year.
Precipitation is linked to pressure systems, meaning that it is wettest at the (low pressure) and driest in the deserts and at the poles (high pressure). There are also regional differences of precipitation within countries; for example, rain shadow in the UK means that the west is wetter than the east. is not evenly distributed around the world, or even within countries, meaning that the demand is not equal throughout the world. Population is concentrated into small areas, such as groups of megacities. There are also differences in demand for water based on development (wealthier countries use more water per capita (per person)). When there is not enough water for sustainable use, the supply is said to be .
water insecurity is where there is not enough water for both people and the environment, and it covers both surface and ground supplies. It can be caused by (arid regions, and short-term variability such as droughts and floods), depleted and degraded water supplies, relief and geology. The annual distribution of rainfall is also a factor (e.g. areas affected by a monsoon climate) – there are very dry parts of the year, when water availability is limited.
In areas, groundwater can be polluted by the salty (saline) ocean water entering the aquifer, making the water unsuitable for drinking unless the salt is removed. This is called saline groundwater intrusion.
Humans are also causing water insecurity through overabstraction. When this occurs on the , abstracting river water reduces streamflow and reduces the water quality, while building and reservoirs floods land, and streamflow below the dam is reduced. The reduced flow also affects aquatic life – there are lower levels of dissolved oxygen, and pollutants are more concentrated (less dispersion). Overabstraction from supplies lowers the water table, and can cause saline seawater to ‘intrude’ into the aquifer, and the base flow of rivers to decrease. The reduced water table also causes ecosystem damage such as vegetation death.
Industrial water affects surface water (e.g. rivers where sewage is discharged) and can contaminate groundwater with heavy metals, including poorly regulated release of sewage in some parts of the world (e.g. China – heavy metals from factory sewage), or heavy metals from mining (including acid mine drainage).
Water is a resource as only a fraction of a percent of Earth’s water is fresh AND available to us.