A technique that enables 24-hour river water level monitoring has been developed by researchers at the University of Bonn. For instance, the affordable sensor is appropriate for flood warning systems that cover a large region. The findings were published in the journal Water Resources Research.
There are many different ways to gauge the level of a watercourse, ranging from very basic ones (using a yardstick or staff gauge) to sophisticated radar systems. All of them, however, have a drawback: the majority of measurement tools can be harmed by direct exposure to high water levels; many do not allow continuous monitoring; remote reading is challenging; or they are just too expensive.
However, a measurement tool without these drawbacks has previously been in use for two years at Wesel in the Lower Rhine: it can continuously communicate the water level via mobile communication to an evaluation center, is affordable, and is dependable. Accordingly, a sensor of this type might theoretically be used to create a widely dispersed network for drought and flood warning systems.
Dr. Makan Karegar of the Institute of Geodesy and Geoinformation at the University of Bonn explains that the basic component of the gadget is a low-cost GNSS receiver and antenna. This sensor has the ability to locate itself conventionally with an accuracy of several meters. It accomplishes this using both the GLONASS and GPS satellites from Russia. However, according to Karegar, “GNSS antenna height above the river level can also be determined using satellite signals.”
Reflected signals provide information on the water level
This is due to the antenna only partially picking up satellite wave transmissions directly. The remainder travels through detour and is reflected from the immediate environment (in this case, the water’s surface). Therefore, this reflected portion goes further. It creates certain interference patterns when superimposed on the directly received signal. These can be used to determine how far away the antenna is from the water’s surface.
As stated by Karegar, “We can mount the GNSS antenna to any structure, whether it be a bridge, a building, a tree, or a fence adjacent to a river.” From there, it can continuously measure the river’s level without touching it, with an average accuracy of about 1.5 cm. “Nevertheless, it is less likely to sustain damage during severe flooding incidents.” The method’s precision is inferior to that of a radar-based sensor. But for the purpose it serves, it is more than adequate. The device is also far less expensive than its high-tech sibling, at just around 150 euros.
A Raspberry Pi is a type of small computer that is linked to the GNSS antenna. According to Prof. Dr. Kristine Larson of the Institute of Geodesy and Geoinformation, “the device is about the size of a small smartphone, yet it has the power to calculate water levels from raw data.” The microcomputer is particularly popular among amateurs, who use it to execute a broad variety of projects thanks to its versatility and low power consumption. It can run entirely independently when fueled by solar cells. Additionally, it may send data over a mobile network.
Reproduction information on the Internet
Larson explains that the “software we built is open source.” “Therefore, anyone can utilize it at no cost.” Additionally, the researchers make all of the material regarding their investigation accessible online. Thus, the measuring tool can be easily replicated by interested parties.
The method does have one drawback, though, in that it can only be used on rivers that are at least 40 meters wide. According to Karegar, this is the shortest radius from which the antenna may pick up the reflected satellite signal. The majority of the reflected signals come from the land if the watercourse is too narrow. However, those concerned intend to improve their assessment code even more. They are hoping that by doing this, they will be able to get accurate findings for smaller rivers like the Ahr in Germany, which was severely flooded in 2021.
Institutions taking part and financial support:
The Federal University of Rio Grande do Sul in Brazil, as well as the University of Bonn, participated in the investigation. The National Council for Scientific and Technological Development of Brazil (CNPq), the German Research Foundation (DFG), and the Rio Grande do Sul State Research Funding Agency all provided funding for the study (Fapergs).
