NASA Satellites Reveal Major Changes In Global Freshwater Supply

Posted: May 17 2018, 3:39pm CDT | by , Updated: May 17 2018, 11:51pm CDT, in News | Latest Science News

 
NASA Satellites Reveal Major Changes in Global Freshwater Supply
This map depicts data collected by NASA's Gravity Recovery and Climate Experiment (GRACE) mission from 2002 to 2016. Credit: NASA

New satellite-based study reveals a disturbing trend in Earth's freshwater distribution

Researchers have used 14 years of observations from NASA’s GRACE mission to track changes in the freshwater supplies of 34 regions around the world and revealed a new, disturbing trend. They have discovered that Earth’s wet areas are getting wetter and dry areas are getting drier and this trend is attributed to a variety of factors including human water management, manmade climate change, and natural climate cycles.

“This is the first time we've assessed how freshwater availability is changing, everywhere on Earth, using satellite observations," said lead author Matt Rodell and chief of the Hydrological Sciences Laboratory at NASA's Goddard Space Flight Center. "A key goal was to distinguish shifts in terrestrial water storage caused by natural variability – wet periods and dry periods associated with El Niño and La Niña, for example – from trends related to climate change or human impacts, like pumping groundwater out of an aquifer faster than it is replenished."

Water is necessary for every aspect of our life from agriculture to household purposes to everyday drinking and exists in the form of lakes, rivers, snow, groundwater and glacial ice. We can find more effective ways to manage our water resources if we can accurately measure them and track the continuous movement of liquid water and ice on Earth. For instance, Southwestern California lost 4 gigatons of freshwater per year during a severe drought from 2007 to 2015. A majority of California's freshwater comes from rainfall and snow that is stored in the Sierra Nevada as snowpack. When natural cycles led to dry years, snowpack and surface water decreased and people became more dependent on groundwater.

Researchers suggest that water loss in some regions is clearly driven by climate change such as melting ice sheets and glaciers. However, the exact reasons can be diverse and have yet to be determined.

"What we are witnessing is major hydrologic change. We see, for the first time, a very distinctive pattern of the wetland areas of the world getting wetter—those are the high latitudes and the tropics—and the dry areas in between getting dryer. Embedded within the dry areas we see multiple hotspots resulting from groundwater depletion,” said co-author James Famiglietti from NASA's Jet Propulsion Laboratory.

“The pattern of wet-getting-wetter, dry-getting-drier is predicted by the Intergovernmental Panel on Climate Change models for the end of the 21st century, but we'll need a much longer dataset to be able to definitely say that climate change is responsible for the emergence of a similar pattern in the GRACE data.”

Launched in 2002, the twin GRACE or Gravity Recovery and Climate Experiment satellites, observed ever-changing distribution of water within and among Earth's atmosphere, oceans, land and ice sheets over the years and transformed our understanding of the global water cycle. GRACE obtained its data by precisely measuring the changes in Earth's gravity field and these changes are caused by the movement of massive amounts of water, ice, and solid Earth. GRACE satellites ceased their operation in October 2017.

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