Technological breakthroughs from the U.S. National Aeronautics and Space Administration (NASA) are changing the possibilities for future water resource measurements. Using satellite-derived data, researchers can now estimate how much water countries have by tracking how their aquifer levels change over time. Researchers Matthew Rodell and Jay Famiglietti first used the Gravity Recovery and Climate Experiment (GRACE) satellite to observe the depletion of the whole U.S. High Plains aquifer.1 Subsequently, the technique has been used to investigate aquifers around the world, showing that everywhere – from California’s Central Valley to northern India’s Rajasthan, Punjab, and Haryana states – precious water supplies are being drained.
The GRACE project, initially started to observe fluctuations in the Earth’s gravity field, uses a pair of satellites that travel in tandem to measure slight changes in their relative distances to each other while they orbit. These variations are caused partly by huge masses of water residing in the world’s water basins, which are large enough to affect the pull of gravity. There are limits to what the satellites can do, however. The spatial resolution for aquifers is roughly only 75,000 square miles, which limits its utility for tracking water resources on a smaller scale. Furthermore, basins don’t necessarily conform to national boundaries, which makes a national policy responses to water loss more difficult.
Still, the satellite data offers empirical measurement free from economic or political drivers, and it is highly time-relevant. In 2011, for example, researchers used GRACE data to monitor the Texas drought and report the local groundwater water levels every week to the American public.5 Perhaps in the future these techniques can be used to communicate just how critical the need is for better water management worldwide.
1 Rodell, M. and Famiglietti, J.S. (2002) The potential for satellite-based monitoring of groundwater storage changes using GRACE: the High Plains aquifer, Central US. Journal of Hydrology 263:245-256.