Groundwater maps produced for the USA

The maps show graphically current levels of groundwater across the USA.  They are based on satellite measurement of fine changes in gravitational attraction, as a pair of satellites passes over.

http://www.nasa.gov/topics/earth/features/tx-drought.html

http://drought.unl.edu/MonitoringTools/NASAGRACEDataAssimilation.aspx

Global groundwater maps would be of immense value.