by Felicity Barringer, NYT, May 30, 2011
IRVINE, Calif. — Scientists have been using small variations in the Earth’s gravity to identify trouble spots around the globe where people are making unsustainable demands on groundwater, one of the planet’s main sources of fresh water. They found problems in places as disparate as North Africa, northern India, northeastern China and the Sacramento–San Joaquin Valley in California, heartland of that state’s $30 billion agricultural industry. Jay S. Famiglietti, director of the University of California’s Center for Hydrologic Modeling here, said the center’s Gravity Recovery and Climate Experiment, known as Grace, relies on the interplay of two nine-year-old twin satellites that monitor each other while orbiting the Earth, thereby producing some of the most precise data ever on the planet’s gravitational variations.
- Precise Geodetic Infrastructure: National Requirements for a Shared Resource (National Research Council), see for example page 41 (Box 3.1 GRACE satellite) and pages 55-58 (Measuring Surface and Groundwater Storage).