On EarthTrends, our mission is to collect international data sets that track global, regional, and national changes over time that relate to the environment and human well-being. One of our greatest challenges has been to collect internationally comparable freshwater statistics; water data sets are typically sparse syntheses from national or regional studies with varying collection and calculation methodologies. (See Ask EarthTrends: Where can I find water use, water pollution, and/or water resources data? for more information on this topic.)
As a result, we are excited to see how NASA's Gravity Recovery and Climate Experiment (GRACE) satellite data have predicted river flows and freshwater storage continuously since 2002, with important applications for both climate and water management policy.
According to Jay Famiglietti, professor of Earth System Science, University of California, Irvine: "Remote sensing of groundwater has been a Holy Grail for hydrologists because it is stored beneath the surface and is not detected by most sensors....Outside of the United States and a few other developed nations, it is not well monitored. It's been speculated that many of Earth's key aquifers are being depleted due to over-exploitation, but a lack of data has hampered efforts to quantify how aquifer levels are changing and take the steps necessary to avoid depleting them. With additional data, such as measurements of surface water and soil moisture, we can use GRACE to solve this problem."
Researchers have not yet fully analyzed this massive data set, but they have already been able to monitor ice melt in Greenland and Antarctica to estimate that sea level rose 1.2 mm between 2002 and 2005. New analysis released this week also showed drying along the Zambezi and Nile basins in Africa. GRACE measurements have also been able to predict water availability for farmers in the Lake Chad basin based on winter snowfall.
RELATED LINKS:
NASA Press Release, 12/12: NASA Outlines Recent Changes in Earth's Freshwater Distribution
Environmental News Service, 12/15: Twin Satellites reveal Earth's Fresh Water Trends
BBC News, 12/13: Satellites weigh Africa's water
