Global Terrestrial Water Storage Anomaly
The gravity variations studied by GRACE can be used to determine ground water storage on land masses. By comparing current data to an average over time, scientists can generate an anomaly map to see where ground water storage has been depleted or increased. Rust colored areas show areas where ground water has decreased, and areas in blue are where ground water levels have increased. Note the significant decreases in ground water storage across most of California and all the way up the North American coast into Alaska.