Steve Elfers, Ian James Using measurements from Earth-observing satellites, NASA scientists have tracked changes in water supplies worldwide and they’ve found that in many places humans are dramatically altering the global water map.
The team of researchers analyzed 14 years of data from NASA’s twin GRACE satellites and studied regions that have seen large increases or decreases in the total amount of freshwater, including water in lakes and rivers and water stored in underground aquifers, soil, snow and ice.
The scientists examined precipitation trends and other data to determine the most likely causes of these huge losses and gains of water around the world.
Their findings in a new study reveal that of the 34 “hotspots” of water change in places from California to China, the trends in about two-thirds of those areas may be linked to climate change or human activities, such as excessive groundwater pumping in farming regions.
“The study shows that humans have really drastically altered the global water landscape in a very profound way.” More: Study: NASA satellites show areas growing drier, wetter In eight of the 34 regions, the researchers said the trends reflect “possible” or “probable” impacts of climate change, including losses of ice sheets in Greenland and Antarctica, precipitation increases in the high latitudes of Eurasia and North America, a retreat of Alaska’s glaciers and melting ice fields in Patagonia.
“In these regions, human impacts are expected to put much bigger pressure on freshwater resources than climate change.” The scientists estimated the water losses and gains in gigatons per year.
And during the 14 years of satellite measurements, nearly all the regions lost or gained at least that much.
“A large portion of them, either direct or indirect human impacts were factors, if not outright the major cause.” In Greenland, where ice is rapidly melting as the planet warms, the researchers estimated water losses at a rate of 279 gigatons per year — an amount equivalent to eight Lake Meads at full capacity, flowing into the oceans and contributing to sea-level rise.
The declining water trends showed up clearly in many of the world’s major food-producing regions, from California and the American Southwest to India, the North China Plain, parts of the Middle East and southern Russia.
The scientists said they found a trend of wet areas getting wetter, especially in the high latitudes and the tropics, and many dry mid-latitude areas getting drier.