Access to water is one of the pressing global issues of the 21st century. As our global population grows and becomes wealthier, the demand for water will greatly increase. At the same time, water availability and quality are also under growing stress from climate change, energy scarcity, land use decisions, and the requirements of industry and minerals processing.
We will need to find better ways to both manage our current use of fresh water and configure it for the future, so as to be able to serve our growing populations and preserve stocks for future generations.
The world’s 6.7 billion people consume about 4,500 km 3 (4.5 teralitres) of freshwater annually, roughly 10% for domestic use, 70% for food production, and 20% for industrial purposes. This total represents less than 5% of that which is annually available through precipitation.
On a global scale, freshwater makes up only about 2.5% of all the water on Earth, or around 35 million km 3 (1 km 3 = 264.2 x 10 9 U.S. gallon). Of this, 95% is fixed in glaciers and ice caps (for now), or found deep underground (less than 1 km below the surface). The remaining 2.5% falls onto the land as rain, of which only about 24% enters the rivers and streams and is accessible as surface water.
Further, a large portion of that precipitation falls in remote areas, leaving only 10% of the total continental precipitation input as easily available for human use (about 9,000–12,000 km3).
Three significant factors impact negatively on the local availability of freshwater. Firstly, climate change induced glacier shrinkage is decreasing the availability of glacial water, threatening groundwater resources with salination due to sea level rises, and endangering forests (which store vast quantities of water), especially through increased wild-fires.
Secondly, growing populations and rapid urbanisation raise water demand due to higher consumption patterns. Thirdly, modern lifestyles promote activities such as high meat consumption that result in the use of large amounts of freshwater. The same is true of some traditional cultures with rice production.
So while we face ever-growing demand for water on the one hand, we face severe supply constraints on the other. Research conducted by the World Resources Institute has found that 41% of the world’s population or 2.3 billion people live in areas subject to frequent water shortages. These are defined as water stressed areas, where per capita water supply is below 1,700 m3 (1,700,000 litres) per year.
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