Human footprints are everywhere in the fresh water of the world. A new study published Wednesday in the journal Nature shows that while man-controlled freshwater sources make up a minimal portion of the world’s ponds, lakes, and rivers, they are responsible for more than half of all changes to the Earth water system.
The study used a new satellite laser technology to take a closer look at freshwater sources around the world and to monitor their water levels in different seasons. Using NASA’s ICESat-2 satellite, researchers monitored more than 227,000 freshwater bodies – from large lakes to small ponds for a period of about a year and a half. The researchers found that 57% of the global variability in seasonal water storage occurs in human-controlled reservoirs.
“This high proportion is even more striking when we consider that reservoirs represent only 3.9% of the 227,386 lakes analyzed in this study,” said Sarah Cooley, lead author of the study, who is currently at the University of California, Berkeley. , but began work while at Brown, said by email. “Although the water cycle is generally described as a natural process, our finding that humans are responsible for most of the seasonal variability in surface water storage shows that we are now a key regulator of the water cycle.”
Before the launch of this satellite in 2018, which was originally designed in order to observe the ice sheets and be able to collect extraordinarily detailed data, it was actually difficult to understand how freshwater bodies changed over time. Cooley said most man-controlled tanks have gauges for measuring water levels, but there is no global database for those measurements. Meanwhile, few lakes and ponds without a reservoir have gauges.
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Satellites before ICESat-2 could only monitor a few hundred of the largest lakes in the world, so the data collected here is quite interesting for people who spend their time thinking about freshwater cycles. “This study provides the first global quantification of surface water level variability and human influence on surface water storage,” Cooley said.
Now that we can see how water cycles around the world behave …and how much they impact people on freshwater reserves – it can tell us a lot about the future and how to improve management. This is especially vital as the climate crisis continues changes the water cycle.
“People who exercise strong control over surface water variability are not inherently a bad thing,” Cooley said, explaining that a human hand in freshwater management is essential in sustaining our lives on the E.arth, including powering hydroelectric dams, irrigating farms and, you know, giving us drinking water. But “increasing the seasonal variability of water storage can certainly have a negative impact on the environment by increasing evapotranspiration and greenhouse gas emissions, degrading water quality, negatively impacting ecosystems and improving downstream erosion.”
Climestone change is already approaching the world’s freshwater supply. The main sources of drinking water, such as The Colorado River, have less water and flow more slowly due to climate change –even as it faces growing demand from our water-hungry farms and towns. Rainfall itself becomes more irregular in some locations, such as California, leading to years with too much water to be handled by the infrastructure and others where the tanks are approaching drying. In December, Wall Street began betting on water as a commodity, because money eagles see the lack of water as a new opportunity to take advantage in the coming decades. With these changes – and the risk of taking advantage of a vital natural resource for life–monitoring what really happens to the water supply will be even more important.
“In order to ensure the sustainability of freshwater resources worldwide, it is valuable, although, to understand where people have the most control over surface water storage, because these may be areas that are more vulnerable in the future, ”said Cooley.