Scientists have devised a new way to measure how much water, in total, flows through all the rivers on Earth. The new methodology provides data that could prove crucial for the future.
A new study by NASA shows how much water is currently in rivers worldwide. Not only that; the same research shows how much water flows through to the ocean and how much water rivers ultimately ‘retain’. Afterwards, the scientists even made it possible to see how these values changed over time. The research shows which areas are most affected by heavy water use – and which areas are getting off fairly mercifully.
Scientist Cédric David contributed to the research. He says: “In recent years, many scientists have tried to make calculations of individual rivers, often looking at how much water ultimately ends up in the ocean. However, there are hardly any studies that look at the total water volume of all rivers together. Before we can manage water properly, we first need to know how much water is available in total. Previously, the situation was a bit like spending money without knowing how much was in the account. It is fundamental to know this.” The research has been published in the journal Nature Geoscience.
Flow meters
The scientists worked rigorously for the research, devising a new methodology. For the research, they combined various measurements from local stream meters with computer models of a total of more than three million river sections. The aforementioned flow meters are mainly present in large and busy rivers, where they measure how fast the water flows and how high the water level is. However, the opposite is also true: unfortunately there are many smaller rivers that do not contain flow meters at all. Not only that; it is also largely unknown how much of the land’s water ultimately ends up in rivers, such as melting snow and ice.
The scientists have come up with a smart solution for all these problems; By looking from space at how high the water level of the various rivers was, it was possible to calculate afterwards how much water left the rivers. To make these calculations possible, the scientists used data from the Shuttle Radar Topography Mission (SRTM). This space mission was carried out in the year 2000, and its aim was to obtain an accurate picture of the different elevations of the Earth.
Subsequent calculations showed that all rivers together contained approximately 2,246 cubic kilometers of water. This is approximately 2.5% of all water on Earth. Of all rivers it contains Amazon Basin most water in South America; 850 cubic kilometers, or 38% of all water in the rivers. The same area also releases the most water of any river on Earth. For example, the river’s ’emissions’ amount to approximately 6,789 cubic kilometers of water per year. All rivers together ‘eject’ approximately 37,411 cubic kilometers of water per year.
Water shortage
The results of the research are significant because they provide tools for policy makers to better manage local water. This is desperately needed: the research shows that there are quite a number of areas that suffer from (local) water use, including Colorado River Basin in the United States, it Amazon Basin in South America and it Orange River Basin in southern Africa. Water use is so heavy in these areas that ultimately less water flows out than comes in. The researchers therefore point out once again that it is very important to keep an eye on the water level worldwide. David concludes: “We can do a lot worldwide to ensure that there is enough water available for everyone. However, we must remember that issues such as the climate crisis and (local) population growth can make this more difficult.”
