Mobile Network Data Used To Measure Rainfall

[alr1970]

Seen in the latest IET Engineering and Technology magazine

http://kn.theiet.org/magazine/issues/1003/news-1003.cfm

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Mobile network data used to measure rainfall

Environmental engineers in Switzerland are using data from a mobile phone network to measure rainfall. The information will be used to help manage wastewater networks and prevent pollution of watercourses.

In built-up areas, unexpected heavy rainfall can overwhelm the drainage system and exceed the capacity of retention basins. Then a mixture of stormwater and untreated effluents is discharged into streams, rivers and lakes, leading to short-term peak pollution levels that can be harmful to algae or fish.

A team from aquatic research centre Eawag are developing a computer model that will build a picture of rainfall intensity with higher resolution in space and time than conventional methods by taking advantage of the fact that raindrops interfere with microwave radio links between base stations. Data provided by mobile communications provider Orange on the attenuation of signal strength is used to calculate the intensity of rainfall along the path between two antennas.

Thanks to the density of the mobile phone network, the resolution of the Eawag rainfall data is superior to that provided by the point measurements of rain gauges or by weather radar. While weather radar can cover a wide area, it has the disadvantage that radar signals are heavily attenuated by intense rainfall. In addition, misleading echoes are generated by the terrain a major problem in a mountainous country like Switzerland.

To apply the method for water pollution control, the researchers analysed data from 23 microwave radio links covering an area of around 150km square in the Zurich region, which has an extensive sewer network. For a two-month period, they compared the data with measurements from 13 rain gauges, two disdrometers (which measure the size distribution of raindrops) and a weather radar station in order to calibrate the model, which can now be used to reconstruct precipitation from radio signal data.

In the near future, project leader J'rg Rieckermann intends to field-test the model in two municipalities. Control systems for retention basins will be linked to local forecasts of precipitation intensity and movement. In at-risk areas, the retention basins will be regulated before and during rainfall events so as to release capacity to cope with the expected water volumes keeping wastewater overflows to a minimum.

Rieckermann points out that Switzerland has a dense mobile telecommunications network, even in remote areas, so accurate rainfall data is widely available. 'Against the background of climate change, this may be crucial. It means that existing reserves can be activated without having to rebuild the drainage system,' he commented.