'Unconventional water sources' could potentially help a quarter of the world's population

　　Fresh water lacks "unconventional water sources" to make up

　　Potential water supply could help a

　　Today's Viewpoint

　　The world faces increasingly complex and intertwined challenges.

In terms of impact, water scarcity is one of the top five global risks, and its impact will extend well beyond socioeconomic challenges, affecting people's livelihoods and well-being.

　　Due to the uneven distribution of freshwater resources and population densities around the world, some regions and countries are already water-stressed.

Growing water scarcity is considered a major cause of conflict, social unrest and migration, while water is increasingly seen as a tool for international cooperation to achieve sustainable development.

With increasing pressure on limited water resources, every available option in water-stressed areas needs to be used sustainably and assessed.

　　On May 26, the United Nations University Institute for Water, Environment and Health (UNU-INWEH), the United Nations University Institute for Material Flux and Integrated Resource Management and the Food and Agriculture Organization of the United Nations jointly published a new book - "Unconventional Water Sources", calling on countries to Harness the planet's abundant "unconventional water sources" - such as those found deep underground or in icebergs - to help a quarter of the world's population facing water shortages for drinking water, sanitation, agriculture and economic development.

　　"Billions of people can benefit from harnessing the potential of unconventional water sources," said Mandor Kadir, the book's editor-in-chief and UNU-INWEH Deputy Director. "These resources are critical to building a future in arid regions."

　　The book identifies six broad categories of unconventional water sources, each of which is obtained in different ways: water harvesting from the air through cloud seeding and mist collectors; freshwater and brackish groundwater extraction offshore and onshore; water reuse; microcollection Rainwater that would otherwise evaporate; full utilization of ship ballast water, or dragging icebergs to physically move water to areas of water scarcity; desalination, etc.

　　At the same time, Kadir emphasized that implementing a national action plan to harness these resources would first require an assessment of environmental trade-offs, as well as a comprehensive cost analysis and innovative financing mechanisms.

　　All-round collection of water sources by sea, land and air

　　The authors note that there is an estimated 13,000 cubic kilometers of water vapor in the atmosphere, and such water sources can be collected from the air and the ground by means of cloud seeding or rain enhancement, and fog collection.

　　Under the right conditions, cloud seeding can increase rainfall by as much as 15 percent.

Research shows that rain enhancement can work at a reasonable cost-benefit ratio.

An increasing number of countries plan to implement rainfall enhancements to address water scarcity and other societal needs.

　　Remote areas in Chile, Morocco and South Africa have been collecting fog using vertical meshes for more than 100 years, with fog collection points on every continent.

In dense fog days, more than 20 liters of drinking water can be collected per square meter of mesh.

At a total cost of less than $250 per square meter for more than ten years, it can produce about 75,000 liters of water per square meter at a cost of just 33 cents per liter.

　　In addition, the authors note that deep groundwater, both offshore and onshore, can be exploited.

The volume of renewable groundwater can be as high as 5 million cubic kilometers, but most of it tends to be brackish.

　　Large quantities of water (estimated 300,000-500,000 cubic kilometers) are contained in aquifers in the shallow waters of continental shelves around the world.

These aquifers are less than 100 kilometers from the sea's surface and were formed millions of years ago when sea levels were low.

Now, a new method of marine electromagnetic surveying provides detailed images of freshwater offshore.

These images, combined with horizontal drilling techniques, can produce economically significant volumes of fresh water that can be pumped to shore for at least 30 years.

　　Deep underground aquifers containing brackish or brackish water also provide the world with millions of cubic kilometers of water.

Israel and Spain are already irrigating high-value crops with desalinated water produced from brackish water.

　　Combining physical and chemical methods to develop water sources

　　Climate change has accelerated the breakup of chunks of ice (icebergs) in the polar regions and the subsequent "ocean-crossing" of icebergs.

The authors note that more than 100,000 Arctic and Antarctic icebergs melt into the ocean each year, with more freshwater than the world consumes.

　　The authors say that using icebergs to produce fresh water is not a new idea, but long-distance iceberg towing has not been attempted because of the significant loss of water volume and the potential rupture of the ice during towing.

However, an analysis of the financial feasibility of towing the iceberg to Cape Town, South Africa, suggests that if the towed iceberg is large enough, 125 million tonnes, it is an economically attractive option.

However, there are other challenges of turning iceberg water into drinking water and environmental impacts.

　　The authors also identified ships as a potential resource, as they discharge about 10 billion tons of ballast water each year.

　　In addition, the authors highlight that desalination and reuse of wastewater can be other important options.

Desalination contributes more than 100 million cubic meters of water every day, feeding about 5% of the world's population.

Although desalination is energy-intensive today, innovative technologies such as nanoparticle-enhanced membranes and forward osmosis are reducing energy input by 20-35%.

　　In terms of wastewater reuse, treated wastewater in many countries is increasingly used to recharge aquifers that provide drinking water.

Treated wastewater provides 25% of the drinking water supply in Windhoek, Namibia, and 40% of Singapore's needs.

San Diego, California and other U.S. cities also get some of their drinking water this way, while Israel and elsewhere use treated wastewater to meet nearly a quarter of their agricultural water needs.