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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    The science behind the life and times of the Earth's salt flats    
      
     Date:   
         May 1, 2023   
     Source:   
         University of Massachusetts Amherst   
     Summary:   
         Researchers have characterized two different types of surface   
         water in the hyperarid salars -- or salt flats -- that contain   
         much of the world's lithium deposits. This new characterization   
         represents a leap forward in understanding how water moves through   
         such basins, and will be key to minimizing the environmental impact   
         on such sensitive, critical habitats.   
      
      
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   FULL STORY   
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   Researchers at the University of Massachusetts Amherst and the University   
   of Alaska Anchorage are the first to characterize two different types of   
   surface water in the hyperarid salars -- or salt flats -- that contain   
   much of the world's lithium deposits. This new characterization represents   
   a leap forward in understanding how water moves through such basins,   
   and will be key to minimizing the environmental impact on such sensitive,   
   critical habitats.   
      
   "You can't protect the salars if you don't first understand how they   
   work," says Sarah McKnight, lead author of the research that appeared   
   recently inWater Resources Research. She completed this work as part of   
   her Ph.D in geosciences at UMass Amherst.   
      
   Think of a salar as a giant, shallow depression into which water is   
   constantly flowing, both through surface runoff but also through the much   
   slower flow of subsurface waters. In this depression, there's no outlet   
   for the water, and because the bowl is in an extremely arid region,   
   the rate of evaporation is such that enormous salt flats have developed   
   over millennia. There are different kinds of water in this depression;   
   generally the nearer the lip of the bowl, the fresher the water. Down   
   near the bottom of the depression, where the salt flats occur, the water   
   is incredibly salty. However, the salt flats are occasionally pocketed   
   with pools of brackish water. Many different kinds of valuable metals   
   can be found in the salt flats -- including lithium -- while the pools   
   of brackish water are critical habitat for animals like flamingoes   
   and vicun~as.   
      
   One of the challenges of studying these systems is that many salars   
   are relatively inaccessible. The one McKnight studies, the Salar   
   de Atacama in Chile, is sandwiched between the Andes and the Atacama   
   Desert. Furthermore, the hydrogeology is incredibly complex: water comes   
   into the system from Andean runoff, as well as via the subsurface aquifer,   
   but the process governing how exactly snow and groundwater eventually   
   turn into salt flat is difficult to pin down.   
      
   Add to this the increased mining pressure in the area and the poorly   
   understood effects it may have on water quality, as well as the   
   mega-storms whose intensity and precipitation has increased markedly   
   due to climate change, and you get a system whose workings are difficult   
   to understand.   
      
   However, combining observations of surface and groundwater with data   
   from the Sentinel-2 satellite and powerful computer modeling, McKnight   
   and her colleagues were able to see something that has so far remained   
   invisible to other researchers.   
      
   It turns out that not all water in the salar is the same. What McKnight   
   and her colleagues call "terminal pools" are brackish ponds of water   
   located in what is called the "transition zone," or the part of the   
   salar where the water is increasingly briny but has not yet reached   
   full concentration. Then there are the "transitional pools," which are   
   located right at the boundary between the briny waters and the salt   
   flats. Water comes into each of these pools from different sources --   
   some of them quite far away from the pools they feed - - and exits the   
   pools via different pathways.   
      
   "It's important to define these two different types of surface waters,"   
   says McKnight, "because they behave very differently. After a major   
   storm event, the terminal pools flood quickly, and then quickly recede   
   back to their pre-flood levels. But the transitional pools take a very   
   long time -- from a few months to almost a year -- to recede back to   
   their normal level after a major storm."  All of this has implications   
   for how these particular ecosystems are managed.   
      
   "We need to treat terminal and transitional pools differently," says   
   McKnight, "which means paying more attention to where the water in the   
   pools comes from and how long it takes to get there."  Parts of this   
   research were funded by the Albemarle Corporation.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Water # Drought_Research # Ecosystems # Floods #   
                   Environmental_Issues # Pollution # Recycling_and_Waste   
                   # Sustainability   
       * RELATED_TERMS   
             o Sea_water o Environmental_impact_assessment o Water_resources   
             o Ocean_surface_wave o Evaporation_from_plants o   
             Underwater_explosion o Desalination o Ecotourism   
      
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   Story Source: Materials provided by   
   University_of_Massachusetts_Amherst. Note: Content may be edited for   
   style and length.   
      
      
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   Journal Reference:   
      1. S. V. McKnight, D. F. Boutt, L. A. Munk, B. Moran. Distinct   
      Hydrologic   
         Pathways Regulate Perennial Surface Water Dynamics in a Hyperarid   
         Basin.   
      
         Water Resources Research, 2023; 59 (4) DOI: 10.1029/2022WR034046   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230501163955.htm   
      
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