Global water crisis: 4 billion thirsty
A recent study led by Eawag researchers sheds light on a growing global crisis: over four billion people—more than half the world’s population—lack access to safely managed drinking water services. This revelation exposes a global health crisis, as billions remain deprived of their most basic human right: clean water.
The study, published in the journal Science, utilised machine learning and a combination of household survey data and Earth observations to present a clearer picture of global water access, particularly in low- and middle-income countries (LMICs).
Access to clean drinking water is a recognised human right and a key component of the United Nations Sustainable Development Goals (SDGs), particularly SDG 6, which aims to ensure the availability and sustainable management of water and sanitation for all by 2030. Yet, as highlighted in this study, the global community faces immense challenges in achieving this goal.
The previous estimates from the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) Joint Monitoring Programme indicated that the number of people lacking safe drinking water was significantly lower at 2.2 billion. However, the new research by Eawag suggests that the actual figure is more than double, underscoring a need for urgent action to address the global water crisis.
New insights from Machine Learning and Earth Observations
The researchers from Eawag, with the support of ETH Zurich, UNICEF, WHO, the Swiss Tropical and Public Health Institute, and the University of Basel, developed a model to estimate safe drinking water access in 135 LMICs. Their work was based on data from over 60,000 households across 27 countries, collected between 2016 and 2020. Using machine learning algorithms, they combined household survey data with geospatial information derived from satellite imagery and Earth observations.
This approach allowed the team to make predictions about the availability, accessibility, and quality of drinking water in regions where data had been sparse or unavailable. The model identified several key predictors of safe drinking water access, including environmental factors like climate and vegetation, as well as human factors such as population density and land use. These predictors were critical in estimating water safety, availability, and accessibility, allowing the team to pinpoint regions that were most at risk.
Lack of safe drinking water in LMICs
The lack of safe water in these countries is further compounded by widespread contamination—faecal matter was found to pollute the water sources of nearly half the population, and a third of people had to fetch water from shared water points. These unsafe practices are not only inconvenient but also contribute to the spread of diseases, impacting public health and quality of life.
The study also found significant regional disparities, with rural areas in low-income countries—particularly in sub-Saharan Africa—facing the most severe water access issues. In several sub-Saharan African countries, less than 10% of the population had access to safely managed drinking water services. These stark figures highlight the immense challenges facing global efforts to ensure universal access to clean drinking water.
Climate change, population density, and water access
The study revealed that climate factors, such as high temperatures and heavy rainfall, were the most important predictors of microbial contamination in drinking water. This finding aligns with existing research showing that extreme weather events can increase the risk of waterborne diseases, especially in regions with poor sanitation infrastructure. As climate change continues to intensify, these challenges are likely to worsen, making it even more difficult to ensure safe water access in vulnerable communities.
Population density and urbanisation also emerged as critical factors in determining water accessibility. In densely populated areas, competition for limited water resources and inadequate infrastructure can lead to significant challenges in delivering safe drinking water. On the other hand, the availability of water for plants—closely linked to local vegetation—was found to be a key predictor of drinking water availability for people. This suggests that regions facing water scarcity for agricultural purposes may also struggle to provide enough drinking water for their populations.
The global map of water insecurity
One of the most valuable outcomes of the study is the global map produced by the researchers, which shows where safely managed drinking water services are most lacking. These maps reveal that many of the most affected regions are in low-income rural areas, where high temperatures and significant seasonal fluctuations in rainfall make it difficult to maintain a consistent and clean water supply.
The map provides a visual representation of the global water crisis, helping policymakers and development agencies prioritise interventions and allocate resources where they are most needed. The fact that so many people in LMICs do not have access to safe drinking water is a wake-up call for the global community.
As Esther Greenwood, lead author of the study, states, “The number of people whose basic human right to safe drinking water is not being met may therefore be significantly underestimated.” These findings challenge existing estimates and call for a reassessment of global water security efforts.
By providing a clearer picture of where drinking water services are most lacking, the research offers valuable insights for governments, international organisations, and development agencies working to achieve universal access to clean water.