NASA’s GRACE Satellites and the Loss of California’s Water Supply
California is melting!—or at least rapidly drying out.
We all know of the melting problems in Greenland, Antarctica, the Swiss Alps and Himalayas. We also know that sea levels are rising and places like Africa and India are facing some heavy water losses. Now, it has been brought to attention that the US state of California has lost nearly 30 cubic kilometers (7.2 cubic miles) of fresh water since 2003. This would be the equivalent of 12 million Olympic-sized swimming pools—7.9 trillion US gallons of water (29 trillion liters).
All of these findings—including the melting ice—come from NASA’s GRACE Satellites: a pair of satellites launched in the spring of 2002, used to map the Earth’s gravity field. These satellites, which have 136.7 miles (220 km) between them, travel in a polar orbit around the globe, at 310 miles (500 km) above the Earth. They are capable of measuring the tiniest gravity changes across the planet; changes that usually stem from the redistribution of water in the soil due to runoff, as well as changes in: ground water aquifers, river flows, melting ice sheets and glacial flow, the circulation of ocean currents and even changes found deep in the Earth’s core.
Moving back to the issue with California’s water loss, you may be wondering why that’s so important—the loss of one state’s water compared to the melting glacial giants of the world. Well, nearly 10% of all US food production (by dollar value) comes from California’s Central Valley. This massive amount of production requires a massive amount of irrigation, which comes from underground aquifers. These aquifers have taken from other water resources in a number of areas. Given some of the nasty effects of global warming, like crazy weather patterns and natural water loss, this has reduced the amount of resources available to the aquifers and as such, has been responsible for changes in the Sierra Nevada, too.
The GRACE Satellite mission is a joint NASA/German Aerospace Center (DLR) program. Those that are part of the program include: The University of Texas Center for Space Research (mission design), NASA JPL (satellite), DLR (launch), and GeoForschungsZentrum Potsdam (operations). If you would like to check out some of the maps and data provided by NASA’s GRACE Satellites, you can do so here.
By Heidi Marshall