With aquifers around the world rapidly becoming depleted due to the widespread use of groundwater, primarily for irrigation, regulation is vitally important. Levels can fluctuate seasonally due to changing patterns of rainfall, snowmelt and extraction, but regulators can only make direct measurements from wells drilled directly into the aquifers. Such wells are rare, compared to the size of most groundwater systems.

Satellite data can be used to measure the movement of the ground above the aquifer as water levels rise and fall, but these data can be rendered inaccurate by the presence of plants, particularly crops, whose heights change on an almost daily basis.

The scientists analysed a decade’s worth of surface-elevation data from the San Luis Valley in Colorado. They produced maps of satellite measurements and found a regular pattern of high- and low-quality data. By overlaying Google Earth images of the farmland, they found that the high-quality data corresponded with dry, crop-free areas. By comparing data from these areas with data collected from local wells, they showed that the satellite results provided an accurate picture of groundwater levels in the aquifers below.

The scientists suggest that this technique can be used in agricultural regions around the world, including areas that lack modern infrastructure such as wells.

February 2011