Water in the Balance

Satellite data may enable improved management of regional groundwater reserves. Earth's climate is changing, and so is its hydrologic cycle. Recent decades have witnessed rising rates of global precipitation, evaporation, and freshwater discharge (1). Extreme flooding is occurring with greater intensity and frequency in some regions; in others, extreme drought is becoming more common (2). Most climate models indicate that by the end of this century, the dry regions of the world will become drier, whereas the wet areas will become wetter (3). Meanwhile, groundwater reserves, the traditional backup for water supplies during extended periods of drought, are in decline globally (4–6). GRACE (the Gravity Recovery and Climate Experiment, a joint U.S.-German satellite mission) monitors these variations on monthly to decadal time scales, providing detailed data on the water cycle that are an essential prerequisite for contemporary water management.

[1]  M. Watkins,et al.  GRACE Measurements of Mass Variability in the Earth System , 2004, Science.

[2]  John Wahr,et al.  Monitoring the water balance of Lake Victoria, East Africa, from space. , 2009 .

[3]  M. Latif,et al.  Intensified Asian Summer Monsoon and its variability in a coupled model forced by increasing greenhouse gas concentrations , 2000 .

[4]  Matthew Rodell,et al.  Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region , 2013, Water resources research.

[5]  V. M. Tiwari,et al.  Dwindling groundwater resources in northern India, from satellite gravity observations , 2009 .

[6]  K. Trenberth.  Changes in precipitation with climate change , 2011 .

[7]  S. Seneviratne,et al.  Global assessment of trends in wetting and drying over land , 2014 .

[8]  W. Winiwarter,et al.  How a century of ammonia synthesis changed the world , 2008 .

[9]  R. Reedy,et al.  Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley , 2012, Proceedings of the National Academy of Sciences.

[10]  S. Wijffels,et al.  Ocean Salinities Reveal Strong Global Water Cycle Intensification During 1950 to 2000 , 2012, Science.

[11]  J. Famiglietti,et al.  Global terrestrial water storage capacity and flood potential using GRACE , 2009 .

[12]  B. Soden,et al.  Robust Responses of the Hydrological Cycle to Global Warming , 2006 .

[13]  C. Sadoff,et al.  Coping with the curse of freshwater variability , 2014, Science.

[14]  Jeremy S. Pal,et al.  Suppression of south Asian summer monsoon precipitation in the 21st century , 2009 .

[15]  F. Chapin,et al.  A safe operating space for humanity , 2009, Nature.

[16]  M. Rodell,et al.  Assimilation of GRACE Terrestrial Water Storage Data into a Land Surface Model: Results for the Mississippi River Basin , 2008 .