What does a responsible use of the available water resources look like in times of a rapidly growing world population? “First of all, it is important to understand which water reserves are available,” says ISOE water expert Stefan Liehr. If we take the global quantity of water that is circulating in the natural cycle as a basis, then around 99 percent is not suitable for supplying drinking water. This is because it is either water frozen in polar ice sheets or glaciers or salt water, which can only be desalinated and converted to drinking water at considerable cost and energy expenditure. “Of the remaining about one percent freshwater that is suitable for consumption, only a tiny fraction comes from rivers and lakes which in many regions of the world are already heavily overused and polluted,” Liehr explains. “The same situation applies to the other, much larger proportion of groundwater. Depending on the region, this water, too, is already heavily overused.”
However, the sufficient availability of good quality water is essential both for the sustainable development of societies and for intact ecosystems. “If we don't want to leave anyone behind with the global water supply, as the United Nations has declared in its sustainability goals, we must consistently reuse water several times,” says water expert Liehr. “Instead of tapping into the last remaining groundwater resources, some of which renew very slowly, we need to establish wastewater as an additional water resource. This will enable us to significantly reduce the pressure on the natural water cycle.”
Reducing pressure on drinking water reserves – recycling wastewater
“A real turnaround in the usage of water towards a sustainable use of all available resources is possible and an important prerequisite for the worldwide supply of water and sanitation,” says Martin Zimmermann, also water researcher at ISOE. Here, the transfer of the circulation principle to the use of water plays a decisive role. Slightly polluted wastewater from households, for example from hand basins and showers, can be treated with comparatively little effort and reused for toilet flushing or garden irrigation. “The core idea of a more sustainable use of water is that drinking water is not needed for all purposes. Different qualities of treated water can also be made available for different needs, ranging from drinking water to water for irrigation, for example,” says Zimmermann.
In countries that are faced with water scarcity, the reuse of water offers great potential, especially with regard to sanitation. “Regulated sanitation not only improves the health situation of the population, but water reuse for irrigation agriculture could also enhance the production of food or animal feed,” reports Zimmermann. Corresponding resource-efficient technologies for the reuse of water are being successfully tested worldwide by ISOE.
Technological and social transformations for global water safety
In order to be able to guarantee water safety on a global scale, however, further components are significant. “To name three: We must continue to implement and test new infrastructure concepts, provide scientific support for appropriate transformation processes with a view to cooperation between the actors involved and, for example, make more consistent use of instruments such as water demand forecasts for rapidly growing megacities,” says Martin Zimmermann. Another relevant aspect of water security is that political decision-makers indeed use research findings and recommendations to develop strategies for sanitation and the sustainable use of water.
In addition to these technical transformations, society is also called upon to change its ways of thinking in order to achieve a water turnaround. “It is important that consumers in industrialized countries, that are considered to be rich in water, better understand the global context of their consumption and then take countermeasures,” explains Stefan Liehr. Because water is not only consumed at home from the tap, but also in “virtual” not so obvious ways that we might not be aware of in everyday life. “By consuming food and other products, such as cotton, which is often grown or produced in countries with far less water, we contribute to overuse precarious water resources and endanger ecosystems in other regions of the world. It is therefore important to raise awareness of this “ecological rucksack” in order to reduce individual water consumption.
Dr. Stefan Liehr
Head of Research Unit Water Resources and Land Use
Phone +49 69 707 69 19-36
Dr. Martin Zimmermann
Head of Research Unit Water Infrastructure and Risk Analyses
Phone: +49 69 707 69 19-44
Phone +49 69 707 69 19-51