New Satellite Method Helps Map Water Underground in Nevada

Groundwater is water stored underground in layers of rock and soil called aquifers. In many areas of the United States and across the globe, more water is being pumped out of aquifers than nature can refill. In the most severe cases, an aquifer's physical structure could collapse, and it could not be refilled.

Researchers at The University of Texas at Austin wanted a better way to learn about these underground layers. They used remote sensing data, which is information collected from far away, along with statistical methods, which are ways of using numbers to find patterns. They used these tools to map a municipal aquifer in Nevada. Permeability is how easily water can move through a material, and the team aimed to create a lower-cost method to measure it.

Pumping water out of an aquifer changes the pressure underground. This can cause the ground above to sink a few millimeters to a few centimeters over months. The study used publicly available InSAR satellite data, which measures tiny changes in the height of the ground from space. The team also used a Bayesian inference algorithm, a method for estimating unknown values from data, that was developed by Omar Ghattas' research group at the Oden Institute.

Using these tools, the researchers created a 3D model of how water is likely to flow and spread sideways through the aquifer. The maps revealed a high-permeability channel on the southern end of the aquifer, which means water can move through it easily. They also found an area of low permeability that previous research had suggested might be a geologic fault, a crack in the Earth's rock.

According to Phys.org, a single InSAR map gave more detailed and accurate information than multiple GPS readings taken over time at this location. The study was published in Geophysical Research Letters.

NASA launched the NISAR satellite with the Indian Space Research Organization last year. This satellite operates on a 12-day repeat cycle, meaning it passes over the same place about every 12 days. It uses longer wavelengths, which can penetrate plant cover. Amal Alghamdi is now an assistant professor at King Fahd University of Petroleum & Minerals.