According to data from the United States Geological Survey on the global distribution of water and its availability, 70% of our planet is water. And 97.5% is salt water, with an estimated total volume of around 1,386 million cubic meters worldwide. However, only 2.5% of this water is fresh water, and even less is suitable for human consumption.
Water is an essential element for life; this is how it is defined by the UN . It is present in the basis of all biological processes and ecosystems, as the key to global balance and the epicenter of sustainable development. Hence, the warning about the Earth’s water stress and the need to manage this precious natural resource efficiently. Fresh water is essential for humans, as it is necessary for food, agriculture, industry, and renewable energy generation, as well as for the environment and biodiversity.
The question is, where are the planet’s fresh water reserves?
The answer is that most of them are frozen in glaciers and ice caps; others are in groundwater, in vast networks of aquifers; and only a small fraction of the total flows through the crust in the form of rivers, lakes, or springs. Lastly, humidity, in the form of invisible rivers that float in the atmosphere, also holds another valuable piece of this blue treasure.
Glaciers and polar ice caps
A large part of the planet's fresh water reserve (around 70%) is frozen in glaciers in Nordic and Austral mountain ranges, and in the polar ice caps, especially in Greenland and Antarctica. In other words, they are the planet's "water towers."
This huge mass of ice is crucial because, when it melts, it feeds river flows and aquifers. Its value is multi-faceted, since as they move, glaciers erode the bedrock and create a "rock flour" that is rich in nutrients for the plants found downstream, thanks to the high concentrations of elements such as iron, phosphorus, zinc, and magnesium. These elements are vital for biological productivity in river and ocean ecosystems.
Groundwater
Approximately another 30% of fresh water is located underground as groundwater, stored in aquifers that are a vital source for agriculture and human consumption, especially in the most arid areas.
These deposits supply 50% of the world's population and 43% of irrigated agriculture. In rural networks, where supply networks sometimes do not reach, inhabitants rely on these wells, just as they are crucial for irrigation in arid areas where dependence on groundwater reaches 90%. According to Unesco, groundwater is a lifeline that allows humanity to adapt to water cycles and their oscillations.
Rivers, lakes and wetlands
Lastly, only a very small fraction (around 0.3% of all fresh water) is in rivers and lakes, in different proportions. This is the most accessible water. This implies, so to speak, that 8 billion people around the planet drink from 0.3% of fresh water on a planet where three-quarters of it is salt water, in seas and oceans.
In this global map of fresh water reserves, the large lakes of the African continent (Victoria, Tanganyika, and Malawi) and North America (Superior, Michigan, Erie, and Ontario) stand out, where 20% of the world's fresh water and 95% of the continent's fresh water is concentrated, alongside the Caspian Sea and Lake Baikal, the deepest and oldest on Earth, in Russia. Together, they account for a large part of this surface water in the Earth's crust.
Atmospheric rivers
Rivers, as we know them, are our main source of supply and represent 0.006% of fresh water. The surprising thing is that the atmosphere still contains more water in the form of vapor (0.04%), vital for the rain cycle. Part of the research now focuses on exploring these atmospheric rivers. The National Oceanic and Atmospheric Administration (NOAA) explores how these water vapor streams floating above our heads are fundamental to hydrological cycles and their role in precipitation.
Lastly, WWF's report indicates that the direct and indirect economic value of fresh water and associated ecosystems exceeds $58 trillion per year, equivalent to 60% of global GDP.
In short, caring for this great blue treasure is vitally important, as it is the world's reserve of fresh water, most of which is frozen, hidden or floating in the air.
