For this year’s World Water Day on March 22nd, the United Nations reminds how closely water and climate change are linked. Increasing global warming is not only leading to a shortage of drinking water resources. It also increases the risk of flooding, especially in cities – and affects the communities in our lakes and rivers. How can the consequences of these changes be mitigated?
Water is simply existential for human life: it does not only play an indispensable role in our body. We could hardly meet many other needs of everyday life without this valuable water – from washing and cooking to watering our fields and fields. Groundwater, rivers and lakes are therefore indispensable for us humans as well as for animals and plants. But these water resources are suffering worldwide. Many waters and groundwater reservoirs are overused. In addition, the entry of pollutants is becoming an increasing problem – also in Germany. Our surface waters in particular are polluted in many places, but there are even pollution in groundwater. “For the groundwater quality, the nitrate and partly also the pesticide pollution from agriculture are the biggest problem”, say Dietrich Borchardt, Markus Further and Karsten Rinke from the Helmholtz Center for Environmental Research (UFZ) in Leipzig.
Climate change is exacerbating the condition of bodies of water, groundwater and water infrastructure. This is exactly what the United Nations wants to draw attention to on this year’s World Water Day on March 22nd. This consequence of global warming is already being felt especially in the cities. Because due to the heat island effect, the urban centers heat up particularly strongly. Persistent periods of heat and drought – as last last summer – mean that the available water resources are becoming scarce, especially in urban areas, while the water requirements of the population are increasing at the same time. Regional bottlenecks in water supply can result. The good news: “We see that the water sector is directly affected by the consequences of climate change, but we also know that there are solutions for adaptation, particularly in the water and wastewater sector,” emphasizes Martina Winker from the Institute for Social-Ecological Research in Frankfurt on the Main river. “Water infrastructures could help make cities more climate-friendly.”
Rinse with rain water
But what could this look like in concrete terms? In order to conserve drinking water supplies, experts recommend using alternative water sources where possible. For example, treated wastewater or rainwater: “We are seeing that acceptance of water reuse is increasing, at home, for example, for flushing the toilet,” reports Winker. The targeted use of alternative water sources to irrigate urban green spaces is increasingly seen as a necessary measure. At the same time, according to the researcher, a fundamental rethink when dealing with water as a resource is also required. In short: we should be less wasteful and handle our water sources more carefully – because in Germany too, this valuable commodity is finite.
But not only water shortages can be a problem. Sometimes too much comes of it at once: We are talking about heavy rainfalls. Such extreme weather events are becoming more common as a result of climate change. In the city, the huge water masses then predominantly hit sealed areas, where they are difficult to infiltrate and lead to flooding. There are also solutions to this problem, as Winker emphasizes. For example, parking lots and sidewalks can be designed so that they can seep away water and thus retain them. Green roofs and rainwater reservoirs help to prevent flooding or at least reduce its size. “For local authorities, it is a matter of examining all these options for climate adaptation and promoting understanding among the population of the necessary measures,” she emphasizes.
“More consistent water protection!”
Effective measures will also be required in the future to meet another challenge of global warming: It has a negative impact on the communities living in the water. “Due to the milder winters, new species can be established that previously only existed in warmer regions. In lakes, warming prolongs the stratification process by starting earlier in the spring and later breaking up in autumn. The limited oxygen reserves in the water have to bridge longer periods of time and the risk of full oxygen consumption increases, ”the UFZ experts around Borchardt list just a few of the consequences.
Among other things, the scientists have already demonstrated that in the course of the heat and drought summer 2018/2019, both fish death due to oxygen depletion and the occurrence of potentially toxic blue-green algal blooms increased compared to previous years. These changes in the water are primarily an ecological problem. However, they also affect the use of water by humans. In large rivers, for example, there is sometimes no water for shipping or bathing bans have to be pronounced due to massive cyanobacteria proliferation. The creed for the coming years is therefore clear: “A much more consistent water protection is required in various areas,” conclude the UFZ researchers.
Sources: Institute for Social-Ecological Research / Helmholtz Center for Environmental Research