What happens when the water runs out

Nine planetary boundaries were defined in 2009 by international scientists led by Johan Rockström – then director of the Resilience Center (SRC) at Stockholm University. They are intended to show how much leeway there is still for man to intervene in natural processes on earth before a dangerous level is reached.

Six of these nine boundaries have already been crossed, including those for climate change, novel entities, land use change, nutrient cycles and the biosphere – and now freshwater. The stratosphere, atmospheric aerosol pollution and ocean acidification are currently not considered to be exceeded.

Photo series with 2 pictures

Visualization of the planetary boundaries with fresh water boundary including green water

PIK/Wang-Erlandsson et al 2022/ORF.at

Six of the nine planetary boundaries have already been crossed

Infographic categorizing water into blue water (ground and surface water), green water (soil water), and gray water (contaminated water)

ORF.at/Sandra Schober

Green water is threatened by human intervention

The freshwater limit must now also be classified as exceeded. Because when the concept of planetary boundaries was introduced, only the availability and situation of “blue” water, i.e. groundwater and surface water such as rivers and lakes, was taken into account. Researchers from the SRC and the Potsdam Institute for Climate Impact Research (PIK) write that a reassessment that also takes into account the “green” water available to plants in the soil has now changed the situation.

Green lungs need soil moisture

“According to the current definition, deforestation, for example, which impairs the function of green water in favor of increased availability of blue water, would not contribute to border crossing,” say the authors. However, the inclusion of green water is essential for the assessment of the situation in the Amazon rainforest, since the rainforest is largely dependent on soil moisture.

Both global warming and deforestation affect the “green lungs of the earth” and dry them out – until the rainforest eventually tips over completely and becomes a steppe. This also has consequences for other earth systems – such as the climate. Because tropical rainforests absorb carbon dioxide from the atmosphere and therefore counteract global warming “like a natural air conditioning system”, according to the nature and environmental protection organization WWF in a press release on the Amazon rainforest.

Heat stress and drought are increasing worldwide

However, according to the researchers from the SRC and PIK, negative effects can already be observed not only in the rainforest, but also in forests and on fields. According to the European Drought Observatory (EDO), the main reason for the increasing dryness of the soil is the lack of precipitation, which – unless it is extreme precipitation – helps dry soil to recover.

Three times a month, the EDO publishes a Soil Drought Index that identifies which areas were both drier and wetter than usual. The index is calculated from the deviation of the green water, i.e. the water content in the soil in the area of ​​the root zone.

European Drought Observatory Soil Drought Index (deviations) for the end of April 2022

At the end of April, the authority recorded particularly dry, but also isolated unusually wet soils in large parts of Europe. The situation was particularly different in Norway, where the coastal soils were very dry, but the interior was particularly wet. Austrian soils – especially in the south – were also significantly drier than usual during this period. For the period from April to June, the EDO is also forecasting “significantly drier weather over southern Europe”. These forecasts give cause for concern about the development of the current drought.

Dry periods have already led to bottlenecks in isolated cases in recent years. Side effects of global warming – such as changes in precipitation, rise in temperature or increased evaporation – also favor dry periods. Water vapor in particular is a little-noticed greenhouse gas that, according to the weekly newspaper “profil”, can act as the “motor of extreme events”.

Green water availability varies

It is difficult to summarize the general situation of green water in Austria, according to Christine Stumpp, head of the Institute for Soil Physics and Agricultural Water Management at the University of Natural Resources and Life Sciences (BOKU): “The water storage in the soil and what is ultimately available for plants can be spatially and temporally vary greatly depending on the weather, the soil properties and the plants.”

In general, a west-east gradient in terms of precipitation can be observed: with more precipitation in the west and at higher altitudes and lower values ​​in the east and on the plains. “More water then seeps into the ground in regions with high precipitation than in regions with less precipitation.”

If the water in the soil is no longer sufficient to achieve good agricultural yields, groundwater and surface water – i.e. blue water – are used for irrigation. “In these regions, natural limits have already been exceeded – at least temporarily,” said Stumpp when asked by ORF.at. But drought and dry soil are also playing an increasing role in some forest regions.

Water demand will increase

In principle, there is a lot of – especially blue – water available in Austria in an international comparison. However, groundwater resources are unevenly distributed. On a long-term average, the rain that falls on the country results in a water volume of 99.8 billion cubic meters. A total of about five percent of this can be used.

According to a study by the Department of Agriculture, this “available groundwater resource” could decrease by up to a quarter by 2050. At the same time, however, the demand for water in agriculture would increase by 2050 and could even double. Because of the increase in hot days, more water is needed for livestock farming – with varying degrees of severity.

The study presents two potential scenarios: In a favorable water scenario, the number of areas with very high utilization increases, but the intensity of utilization remains below 100 percent everywhere. In an unfavorable scenario, the intensity of use increases in some regions and the demand consequently exceeds the available groundwater resources, which could result in regional conflicts over use.

Seasonal snow cover decreases

The ability of the snow cover to reflect solar energy and store water is also essential for the functioning and regulation of the climate, analyzes the Central Institute for Meteorology and Geodynamics (ZAMG) on its website. During the winter, water is held back in the snow cover, which is slowly released again over days and weeks as the snow melts. The groundwater reservoirs are thus filled and the soil is also supplied with the melted water – the soil and the plants are thus prepared for the growth period in spring.

Conversely, this means that with less snow in winter, the water supply to the soil is impaired. This leads to low groundwater levels and problems in agriculture. In addition, a layer of snow prevents the heat stored in the ground from being radiated into the comparatively cooler atmosphere. This also insulates plants and protects them from frost.

Glacier melt in Austria from 1969 to 2015

Analyzes by the ZAMG in various areas of Austria show that the winter snow cover varies greatly from year to year and also spatially. However, a significant decrease in seasonal snow depth from the late 1980s is clearly recognizable – presumably due to a combined effect of temperature increase and decrease in precipitation. It snows significantly less, especially at lower altitudes. Winter begins later in autumn and ends earlier in spring.

Meat consumption increases water consumption

There is a wide range of possible water protection measures. On the one hand, the reduction in greenhouse gas emissions makes a significant contribution to curbing global warming by 1.5 degrees – which also defuses the dynamics of drought and dry soil. Individuals can make a contribution here, for example through their diet.

“The high meat consumption is the main driver that the planet has exceeded its limits in terms of freshwater availability, rainforest deforestation, biodiversity and greenhouse gas emissions,” says Martin Schlatzer, nutritional ecologist at the Research Institute of Organic Farming (FiBL), in a WWF action plan. Even reducing meat consumption to once or twice a week could save almost a third of greenhouse gases.

The Austrian Climate Research Network (CCCA) also summarizes concrete measures for the protection of – above all green – water in a fact sheet. To date, drinking water has been used almost exclusively for additional watering of plants in Austria. According to the CCCA, storing rainwater and reusing water from the bathroom and kitchen would be more efficient.

Water protection and soil sealing

Since cultivating the natural soil affects both the green water and the groundwater, the WWF package of measures for the “Water Treasure East Austria” calls for the soil to be consistently protected and unsealed. Rivers need to be renatured, wetlands and flood plains need to be preserved and restored.

Landscape near Salzburg

ORF.at/Georg Hummer

If natural surfaces are built on, the water can no longer seep into the ground

The Federal Environment Agency summarizes the plans of the Ministry of Agriculture and Climate for the infiltration of rainwater on one’s own land. And water retention measures such as rainwater retention basins or targeted groundwater recharge are already being planned or implemented.

It is essential that the available water is used more efficiently. With the help of water-saving technologies in new household appliances, water consumption can remain constant despite an increasing population. At the same time, information on the development of demand and water resources needs to be compiled and the data on current water withdrawal needs to be improved. Water withdrawal quantities that have already been approved should be checked and, if necessary, adjusted to reflect current developments.

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