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GPS sensors measure how much water is stored in snow

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Snow is an important water resource. To find out how much water is stored in a snowpack, researchers measure the so-called snow water equivalent (SWE). This value is needed, for example, to predict the amount of melt water in spring, but it is difficult to determine. Up until now, measuring it automatically has required large and expensive devices.

Researchers from Ludwig Maximilian University in Munich and the University of Natural Resources and Life Sciences in Vienna, together with SLF researchers, have developed a new method for measuring SWE simply and cost-effectively using conventional GPS sensors. To test it, they installed two GPS antennas on the SLF test site at Weissfluhjoch above Davos. The one on the ground got buried in snow during the winter. The other, on a mast, remained snow-free and served as a reference. If the GPS signal passes through the snow cover, the characteristics of the signal change. It becomes weaker and slows down. The researchers were able to calculate the SWE from the difference between the signals received above and below the snowpack. In addition, it was possible to derive the snow depth and liquid water content of the snowpack.

“For the first time it was possible to measure all three parameters using just one method,” says SLF Director, Jürg Schweizer. The values obtained correspond well with those from conventional reference measurements. Thus GPS sensors may one day be used to measure the three snow parameters in many different places quite cheaply. But before the new method can be put into practice, it needs to be further tested and improved. This is why the researchers are now carrying out further measurements at three additional sites located between 815 and 1520 metres above sea level. (Claudia Hoffmann, Diagonal 1/19)