Worldwide, water resources are under increasing pressure. On the one hand, climate change is intensifying the global hydrological cycle, causing water extremes such as droughts and floods to become more frequent and more pronounced. On the other hand, social patterns of water use are changing with resulting conflicts over resources. Against this background, ensuring a secure water supply today and in the future is a major challenge.
“In order to explore solutions for adapting to the coming changes in the global water balance, it is necessary to take stock of the available water resources, both at global and at regional level,” says Robert Lütkemeier, head of ISOE’s Research Unit Water and Land Use. “We need to know the demand as well as the quantities and quality of our water resources if economic and innovation-oriented policy measures are to be effective.”
Global water stress with varying regional stress levels
For the focal study “Innovations in water management” of the EFI report, Robert Lütkemeier and co-author Ahmad Awad reviewed the scientific knowledge on the state of the world’s water resources. To assess the globally available water quantity, the researchers analyzed observational data from various platforms such as FAO Aquastat and EUROSTAT, as well as model data from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), which offer insights into past, present and expected future conditions. To estimate the extent of the anticipated water stress, the ISOE team created simulations of water withdrawals and compared these with data on renewable water resources.
“In principle, the assessment of water stress and a specific prediction of future changes are subject to uncertainties due to the limited available observational data and possible socio-economic fluctuations,” emphasizes Lütkemeier. The results of ISOE’s study “The Status of Global Freshwater Resources” do, however, indicate a decline in renewable water resources in dry and subtropical regions, such as the Mediterranean area. By contrast, an increase is to be expected in the wetter regions of the temperate latitudes and in monsoon areas.
“Currently, we have to assume that global water stress will increase, although forecasts vary greatly from country to country,” says Lütkemeier. “With regard to Germany, however, we see that, in particular, the reduced water withdrawals in the energy sector have been able to reduce the general level of water stress, although, here as well, water stress can also vary greatly from region to region.” Risks therefore also persist for Germany in terms of water supply. “Extreme events such as droughts and floods, as caused and exacerbated by climate change, continue to be a major cause for concern.”
Just over half of all water bodies worldwide meet quality standards
To assess water quality, the ISOE researchers compiled indicators from the Sustainable Development Goals’ monitoring program and data from the Water Framework Directive monitoring programs. The results show major regional differences in water quality: Worldwide, only 56 percent of water bodies meet the general quality standards set by the Sustainable Development Goals, which relate to the levels of oxygen, salinity, nitrogen, phosphorus and pH.
“It is surprising that a significant proportion of water bodies with poor quality are located in the Global North, in spite of significantly better wastewater treatment technologies than in the Global South,” reports Lütkemeier. For example, the data, although scant at times, show good water quality for sub-Saharan Africa.
In Germany, despite progress in combating pollution caused by chemical contaminants, nutrient pollution and by hazardous waste from the past such as mercury, the majority of water bodies are significantly polluted. “Only nine percent of surface waters meet good ecological standards,” reports Lütkemeier. “Additionally, groundwater is in many places contaminated by nitrates and pesticides which poses risks for drinking water and ecosystems.”
Responsible management of available water resources
The authors Robert Lütkemeier and Ahmad Awad strongly recommend establishing integrated and adaptable water management strategies. “The goal must be responsible management of available water resources. And that means countering the effects of climate change in the water sector, taking into account future socio-economic developments, and curbing environmental pollution,” says Lütkemeier. Here, targeted cooperation between interest groups and governments is crucial. All parties concerned must strive to ensure long-term and effective resource protection and promote not only technological, but also organizational and social innovations.
In order to ensure sustainable water management for future generations, it is also essential to improve the quality and availability of scientific data. “Policymakers, administrators and business leaders need reliable forecasts that require adequate amounts of data as a basic prerequisite,” emphasizes Lütkemeier. Especially in regions already threatened by shortages, the lack of valid data is proving to be extremely problematic for achieving the goal of secure water supply.
Link to the study Luetkemeier, R.; Ahmad, A. (2025): The Status of Global Freshwater Resources. Studien zum deutschen Innovationssystem. Nr. 8-2025. Berlin: EFI.
https://www.e-fi.de/fileadmin/Assets/Studien/2025/StuDIS_08_2025_.pdf
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Figure 1 (Water Stress Median 2015–2025): Water stress in the current situation
Figure 2 (Water Stress Median 2090–2100): Projected water stress for the future
Figure 3 (Water Stress Change): Change in water stress (Water Stress Change) comparing the future period 2090–2100 with the current period 2015–2025
Source: Luetkemeier & Awad (2025): “The Status of Global Freshwater Resources”: 15
Scientific contact:
Dr. Robert Lütkemeier
Tel. +49 69 707 6919-58
robert.luetkemeier@isoe.de
www.isoe.de
Press contact:
Melanie Neugart
Tel. +49 69 707 6919-51
melanie.neugart(at)isoe.de
www.isoe.de