BY CAITLIN DEMPSEY MORAIS
Scientists at NASA’s Goddard Space Flight Center have been experimenting with a new data product to assess groundwater and soil moisture drought indicators. The maps produced are used by the U.S. Drought Monitor and use data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites.
In 2002, the GRACE satellites were launched with the capability of measuring above ground and below ground terrestrial water storage by observing small changes in Earth’s mass and its gravity field which are affected by the movement and storage of water and ice around the planet. By combing GRACE measurements with other ground- and space-based meteorological observations (precipitation, solar radiation, etc.), scientists are able to calculate soil moisture and groundwater storage which is then compared to the averages from 1948 to 2009.
The map below shows a comparison of modeled relative amount of water stored in underground aquifers in the continental United States for July 7, 2014 as compared to the average for comparable weeks for the sixty year average water storage. Areas where the wetness, or water content, are higher than the average are shaded blue and areas where the wetness is less than the average are shaded red.
GRACE BASED SHALLOW GROUNDWATER DROUGHT INDICATOR MAP FOR JULY 7, 2014. SOURCE: NASA.
The results of the map underpin the severe drought that has been affecting the Southwest United States. California, Nevada, New Mexico, Colorado, Texas, Arizona, Oklahoma, and Nebraska all have been suffering from a long-term drought that has hindered the replenishment of its underground aquifers.
So far there are three GRACE-based map products available from the National Drought Mitigation Center: groundwater percentile, root zone soil moisture percentile, and surface soil moisture percentile. The maps produced only reflect drought conditions as affected by climatic variability and don’t factor in depletion caused by man-made activities such as well drilling.
References
NASA Earth Observatory (2012, September 12) The Gravity of Water.
National Drought Mitigation Center (2014, July 21) Groundwater and Soil Moisture Conditions from GRACE Data Assimilation. Accessed July 23, 2014.
NASA (July 2014) Groundwater Deficit Out West
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