Last Wednesday, Tufts Department of Earth and Ocean Sciences was visited by UC Irvine professor and NASA water scientist Jay Famiglietti. His talk, titled “Observing the Epic California Drought and Groundwater Depletion from Space” was based on articles “The Global Groundwater Crisis” and “Satellites Measure Recent Rates of Groundwater Depletion in California’s Central Valley.”
Famiglietti began with a timeline of the California Drought, beginning with January 2014’s declaration of of a drought emergency. This was followed by a series of cuts in surface water allocation. Despite efforts, groundwater levels have continue to drop. Governor Brown’s continued attempts to mitigate the situation led to his freeing up drought relief funds and the signing of historic groundwater management legislation.
On the technical side, Famiglietti outlined the methods and instrumentation for his analysis. NASA’s Gravity Recovery Climate Experiment (GRACE) was launched in 2002 as a “scale in the sky” to weigh monthly changes in groundwater storage around the globe. Since water is much heavier than most other earth components, and its local mass fluctuates more drastically than other geological features, GRACE satellites are able to accurately measure these fluctuations in an areas gravitational field. Subtracting known or estimated changes in surface water, snow and soil moisture, scientists can quantify changes in groundwater level over time.
California’s position as a highly productive agricultural region makes this an important research area with international implications, but Famiglietti’s work isn’t limited to that geographic area. The Middle East, North China, the rest of the American Southwest, and other areas are sharing similar experiences. He notes that parts of northwestern India are experiencing the greatest rate of groundwater depletion in the world. With 33% of total water use and half of all agricultural use worldwide coming from groundwater sources, predictions of continued drought mean that action must be taken to better manage our water resources.