Water scarcity--defined as the annual availability of less than 1,000 cubic meters of water per person--already affects 40 percent of the world population. By 2025, this figure could rise to 66 percent as a result of population growth, climate change and water pollution. What if we could turn seawater, which accounts for 97 percent of the earth's water resources, into drinkable water? We can. Desalination technologies have existed for hundreds of years, although the cost of desalination remains prohibitively high for most countries.
Projected Annual Renewable Water Supply Per Person by River Basin, 2025
Source: EarthTrends
How does it work?
Desalination technologies range in size and type from family sized solar powered distillers to large-scale commercial plants. No matter what type of technology is being used, the process is roughly the same: saltwater and energy are fed into a system and freshwater plus a highly concentrated waste are produced. The cost, energy requirements, and the amount of pure water that can be obtained vary widely for different technologies. The leading methodologies today are reverse osmosis (a membrane process) and multi-stage flash (a distillation process). Other processes include geothermal desalination and solar humidification
Who is doing it?
In the most water scarce regions of the world, including North Africa, the Middle East, and several island nations, desalination has become a vital source of water. Saudi Arabia is currently the world leader, with 27 desalination plants providing 70 percent of the country's drinking water requirement. Furthermore, countries including Japan, Germany and the United States continue to invest in improving desalination technology, making it more efficient and cost effective.
View country level data for desalinated water production at EarthTrends.
Is it the solution to water scarcity?
Despite technological improvements, desalinated water costs roughly five times more to produce than drinking water from typical sources, although the price varies widely depending on the salinity of the input water, the energy requirements of the process, the toxicity of the final waste product, and the distance that the freshwater must be transported. Although the price will likely decrease with future research, it is unlikely that desalination will be the ultimate solution to water scarcity problems, particularly in the developing world. However, it will certainly continue to play an important role in affluent yet water scarce countries with large coastal populations.
Related Links:
U.S. Geological Survey (USGS) information on desalination
"Water Desalination Takes a Step Forward"
International Water Management Institute
United Nations Environment Programme (UNEP) Freshwater Website
EarthTrends
Data Table: Groundwater and Desalination 2000
Water Resources and Freshwater Ecosystems Searchable Database
