Saturday, June 9, 2018

NASA satellites reveal major shifts in global freshwater

News | May 29, 2018  
Time series showing global freshwater trends as measured by the NASA/German Aerospace Center (DLR) Gravity Recovery and Climate Experiment mission from 2002 to 2016. Freshwater increases above average are shown in blue, while decreases below average are in red. Credit: NASA's Scientific Visualization Studio › Full view
In a first-of-its-kind study, scientists have combined an array of NASA satellite observations of Earth with data on human activities to map locations where freshwater is changing around the globe and why.
The study, published today in the journal Nature, finds that Earth's wet land areas are getting wetter and dry areas are getting drier due to a variety of factors, including human water management, climate change and natural cycles.
Between 2002 and 2016, the Gravity Recovery and Climate Experiment (GRACE) tracked the movement of freshwater around the planet. Credit: NASA's Goddard Space Flight Center/Katy Mersmann 
Between 2002 and 2016, the Gravity Recovery and Climate Experiment (GRACE) tracked the movement of freshwater around the planet. Credit: NASA's Goddard Space Flight Center/Katy Mersmann
A team led by Matt Rodell of NASA's Goddard Space Flight Center in Greenbelt, Maryland, used 14 years of observations from the U.S./German-led Gravity Recovery and Climate Experiment (GRACE) spacecraft mission to track global trends in freshwater in 34 regions around the world. To understand why these trends emerged, they needed to pull in satellite precipitation data from the Global Precipitation Climatology Project, NASA/U.S. Geological Survey Landsat imagery, irrigation maps, and published reports of human activities related to agriculture, mining and reservoir operations. Only through analysis of the combined data sets were the scientists able to get a full understanding of the reasons for Earth's freshwater changes, as well as the sizes of those trends.
"This is the first time that we've used observations from multiple satellites in a thorough assessment of how freshwater availability is changing everywhere on Earth," said Rodell. "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."
Freshwater is found in lakes, rivers, soil, snow, groundwater and ice. Freshwater loss from the ice sheets at the poles -- attributed to climate change -- has implications for sea level rise. On land, freshwater is one of the most essential of Earth's resources, for drinking water and agriculture. While some regions' water supplies are relatively stable, others experienced increases or decreases.
"What we are witnessing is major hydrologic change," said co-author Jay Famiglietti of NASA's Jet Propulsion Laboratory in Pasadena, California, which also managed the GRACE mission for NASA's Science Mission Directorate in Washington. "We see a distinctive pattern of the wet land 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."
Famiglietti noted that while water loss in some regions, like the melting ice sheets and alpine glaciers, is clearly driven by warming climate, it will require more time and data to determine the driving forces behind other patterns of freshwater change.
"The pattern of wet-getting-wetter, dry-getting-drier during the rest of the 21st century is predicted by the Intergovernmental Panel on Climate Change models, but we'll need a much longer dataset to be able to definitively say whether climate change is responsible for the emergence of any similar pattern in the GRACE data," Famiglietti said.
The twin GRACE satellites, launched in 2002 as a joint mission with the German Aerospace Center (DLR), precisely measured the distance between the two spacecraft to detect changes in Earth's gravity field caused by movements of mass on the planet below. Using this method, GRACE tracked monthly variations in terrestrial water storage until its science mission ended in October 2017.
Artist's illustration of the twin spacecraft of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission. GRACE Follow-On will soon continue the legacy of the original GRACE mission, providing valuable data that will help manage Earth's critical water resources. › Full image and caption 
However, the GRACE satellite observations alone couldn't tell Rodell, Famiglietti and their colleagues what was causing the apparent trends.
"We examined information on precipitation, agriculture and groundwater pumping to find a possible explanation for the trends estimated from GRACE," said co-author Hiroko Beaudoing of Goddard and the University of Maryland in College Park.
For instance, although pumping groundwater for agricultural uses is a significant contributor to freshwater depletion throughout the world, groundwater levels are also sensitive to cycles of persistent drought or rainy conditions. Famiglietti noted that such a combination was likely the cause of the significant groundwater depletion observed in California's Central Valley from 2007 to 2015, when decreased groundwater replenishment from rain and snowfall combined with increased pumping for agriculture.
Southwestern California lost 4 gigatons of freshwater per year during the period. A gigaton of water would fill 400,000 Olympic swimming pools. A majority of California's freshwater comes in the form of rainfall and snow that collect in the Sierra Nevada snowpack and then is managed as it melts into surface waters through a series of reservoirs. When natural cycles led to less precipitation and caused diminished snowpack and surface waters, people relied on groundwater more heavily.
Downward trends in freshwater seen in Saudi Arabia also reflect agricultural pressures. From 2002 to 2016, the region lost 6.1 gigatons per year of stored groundwater. Imagery from Landsat satellites shows an explosive growth of irrigated farmland in the arid landscape from 1987 to the present, which may explain the increased drawdown.
The team's analyses also identified large, decade-long trends in terrestrial freshwater storage that do not appear to be directly related to human activities. Natural cycles of high or low rainfall can cause a trend that is unlikely to persist, Rodell said. An example is Africa's western Zambezi basin and Okavango Delta, a vital watering hole for wildlife in northern Botswana. In this region, water storage increased at an average rate of 29 gigatons per year from 2002 to 2016. This wet period during the GRACE mission followed at least two decades of dryness. Rodell believes it is a case of natural variability that occurs over decades in this region of Africa.
The researchers found that a combination of natural and human pressures can lead to complex scenarios in some regions. Xinjiang province in northwestern China, about the size of Kansas, is bordered by Kazakhstan to the west and the Taklamakan desert to the south and encompasses the central portion of the Tien Shan Mountains. During the first decades of this century, previously undocumented water declines occurred in Xinjiang.
Rodell and his colleagues pieced together multiple factors to explain the loss of 5.5 gigatons of terrestrial water storage per year in Xinjiang province. Less rainfall was not the culprit. Additions to surface water were also occurring from climate change-induced glacier melt, and the pumping of groundwater out of coal mines. But these additions were more than offset by depletions caused by an increase in water consumption by irrigated cropland and evaporation of river water from the desert floor.
The successor to GRACE, called GRACE Follow-On, a joint mission with the German Research Centre for Geosciences (GFZ), currently is at Vandenberg Air Force Base in California undergoing final preparations for launch no earlier than May 22.
For more information on how NASA studies Earth, visit:
Thank NASA

Knight Jonny C.


  1. What great information Jonny. I learned a lot from your post. NASA is an amazing organization. Their science is way ahead of the rest of the world. And do you notice that in spite of Cheeto Man's attitude to climate change, NASA keeps right on researching it and developing ways to track it( Grace). And they have the next generation Grace ready to go.
    You see how much greater the climate change is in Canada on your chart. We have most of the fresh water in the world up here. It will be one of the greatest resources for the world in the future. By the way, that is an awesome chart.
    I believe that Central Africa will become a desert completely and permanently. They will have almost no fresh water and they don't possess the technology to tap the water thousands of feet under the earth.
    Such a great post Knight Jonny. I am making a copy for myself. I have copies of a lot of the Knights' articles. You guys are bringing Knowledge to the ignorant.
    Luv Aunt Jeannie

    1. Knight aunt Jeannie,
      My instructor at Sci-Port told me about this article , he said since I was studying about NASA and what they were doing he was going to direct me into how and what NASA is doing to help climate change Professor Morris said it was a good idea to go back to refresh people memories even if Mr. Trump says it's fake , He said that the scientists want is money . I told him the scientists had to have money to operate ,Professor said Mr. Trump say scientists make fake finding do they can collect money and don't have to work .
      I asked mama did she think it was possible for Mr.Trump to go 24 hours without telling a lie . Mama asked can you get blood out of a rock , I answered no , mama looked at me smiling , she said well you answer your own question .
      Uncle Jon was talking about central Africa last week at the round table that was hid belief , it may happen sooner that most people think .
      We are very pleased and honored that you make copies for yourself , daddy sole us something poppa told him when he was about my age , he found it was a very remarkable piece of advice ; something of interesting that you read it ,put it away at a later date , read it again , you will always learn something that you missed the first time .
      We do hope we are reaching people , Aunt Jeannie you may be right about bring knowledge to the ignorant or maybe a lot of people in the south and western states that is hot . mama said you made her take notice with just one post about the bears and she is still fighting and now she has 4 kids , nieces , nephews , brother in training to be Knights , uncle Jon thinks it best for them to be reporter Knights and when we post their stories we will give them credit , they all agreed except Lynn she don't know what we are talking about she is only 3 , Man gave her a cookie and she agreed .
      Thank you very much .
      Love to you and uncle Brian
      Knight Jonny C.

  2. Howdy Knight Jonny,
    This post id terrific , you guys learn well from your poppa , he taught you to dig for information , as poppa said there are a lot of important information out there .
    I see you are getting a lot of stuff with the help of your NASA instructors .
    I enjoyed reading this post , I want the deniers to know NASA has a lot of scientists on their team .
    Like aunt Jeannie I also learned a lot from your post .
    Any idea when Man is going to do his post ? I asked him he said soon ... when is soon ... he showed me one he is doing on climate change , if I do say so myself , he is smart Hahahahaha!!!!
    Great post sweetie , love you thiiiiiiiiiiiiiis much.
    Knight Mama

    1. Hi Mama Knight,
      Thank you very much , poppa taught us a lot of things abut surviving in this wicked world , His letter to me will last through my lifetime , it tells about the ups and downs and tell me how to get around the pitfalls . One of my classmates told professor Morris , he didn't want to go to college or a university he wanted to go to a trade school , he wanted to be a mechanic and own his own shop and maybe start a truck hauling company .
      Jenny is right lots of parents don't listen at their kids they know what they want them to be it really don't matter what the kids want , he asked us what he should do , I told him I knew when I was about 8 or 9 what I wanted and so did my sisters , we asked Man he said he was going to be like poppa and daddy so we still don't know .
      Daddy don't go out of town much , and is here to help Man , we asked daddy when was soon , daddy said said he think Man is looking for the right picture to go with his poppa post , he could tell Sha what he want , she would draw it for him .
      Thank you I enjoyed doing this one .
      Love you Knight Mama for just being you .
      Knight Jonny C.

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