The new holistic monitoring system developed under the leadership of TU Graz measures boat waves with millimetre precision using satellite navigation data and sensors on buoys and for the first time allows investigations into the extent to which boat traffic, weather and other factors influence the ecosystem of lakes.
Motorboats, sightseeing boats, shoreline obstructions and meteorological changes caused by climate change are putting lakes under increasing pressure. The weakening of lake ecosystems is reflected in a shift in species diversity and a decline in ecological functionality. This also affects three of Carinthia’s largest lakes: Lake Wörthersee, Lake Ossiach and Lake Weißensee.
In order to get to the bottom of these changes in ecosystems, researchers at TU Graz have now developed a new type of measurement and simulation system for recording and evaluating the waves of lakes and their ecological effects together with partners as part of the WAMOS (wave monitoring system based on GNSS/INS integration) project. For the first time, the system enables precise analyses of how strongly boat waves and wind waves influence the ecological balance of lakes and makes it possible to determine which shore areas are particularly affected.
The results show that waves caused by boats have a significant impact on the ecological functioning of the lake. “For the first time, we were able to scientifically prove how much motorboat waves contribute to the stirring up of sediments and thus to the turbidity of the water and, in particular, to the underwater plants,” says Philipp Berglez from the Institute of Geodesy at TU Graz.
Waves measured to the closest millimetre
The monitoring system was developed for the Wörthersee and also tested there. Lake Wörthersee was selected as a test area due to the high number of boat licences. The number of boat licences for motorboats on Carinthia’s largest lake more than doubled between 2007 and 2025, from 400 to around 900.
To determine the heights of the waves, the team from Graz University of Technology (TU Graz) equipped buoys with sensors for precise positioning and movement determination using satellite positioning (GNSS) and acceleration sensors (INS). The sensor data from the buoys recorded in this way is used to calculate the wave height.
Laboratory and field tests show that the buoys measure the sea waves with an overall accuracy of less than 10 millimetres. “This is an absolute novelty. Until now, measuring buoys for determining wave height have been designed for maritime applications such as tsunami warnings and are nowhere near as accurate for measuring the much smaller wave movements in the lake,” explains Philipp Berglez.
In addition to the height, the monitoring system also determines the cause of the waves – motorboats or wind. This is a particular challenge on Lake Wörthersee because the high-frequency components of wind and boat waves are similar. A specially developed filter emphasises typical boat wave patterns so that they can be clearly distinguished in the data.
AI recognises boats automatically
Another innovative component of the WAMOS system is an AI-based boat recognition system that automatically distinguishes between motorboats, sailing boats and ships from drone images to an accuracy of around 96 per cent. This was contributed by the Carinthia University of Applied Sciences. This makes it possible to precisely assign the generated waveforms and their energy to a particular cause and thus to model the effects of boat traffic on the ecosystem.
Parallel to the wave measurements, the Viennese limnology company systema carried out extensive aquatic ecology studies, including turbidity measurements and macrophyte monitoring over two vegetation periods. These aquatic plants serve as bio-indicators for the ecological status of a body of water.
The German engineering firm Kobus und Partner also contributed meteorological surveys and integrated all the results and statements into a wave atlas. This wave atlas visualises the surface waves and shows how strongly exposed the shore areas are, taking into account shoreline obstructions and wind conditions. In addition, a boat model was developed to simulate individual scenarios, into which all measurements were incorporated.
Natural protective measures are the most effective
The investigations provided initial information on the effectiveness of protective measures. Protective reed fences are effective in that they keep strong waves away from the shore belt, allowing plants to colonise and spread. Due to their high wave energy, boat waves and their degree of attenuation can even be detected by reed fences. “However, natural unspoilt bays clearly offer the best protection,” emphasises Philipp Berglez. Lakes with heavily built-up shores, such as the Wörthersee, have not been in their original state for a long time and therefore offer less natural wave protection.
Fish factor
In the course of its investigations, the project team was able to confirm one assumption: in addition to the waves and associated currents, fish are also a significant factor in the loss of macrophytes. Carp, roach and rudd are a major threat to plant stocks, both by feeding and by stirring up the sediment. The agitated sediment is also transported by the wave action and is deposited on the aquatic plants. This impairs photosynthesis, which further weakens the underwater plants. Berglez summarises: “In combination with boat waves, this leads to a dangerous downward spiral for plant populations.”
The developed lake models utilise all these results and allow statements and simulations to be made for the entire lake based on selective measurements. WAMOS thus provides a sound basis for data-based and sustainable lake management. The aim now is to further develop the monitoring concept and to collect long-term data on other lakes as well.
About the WAMOS project:
The research project WAMOS (wave monitoring system based on GNSS/INS integration; Proj. No. FO999900575) was developed by TU Graz (Institute of Geodesy and Institute of Hydraulic Engineering and Water Resources Management) in cooperation with the Carinthia University of Applied Sciences (SIENA research group), systema Bio- und Management Consulting GmbH and the engineering company Prof. Kobus & Partner GmbH and funded by the Austrian Research Promotion Agency (FFG) in the Austrian Space Applications Programme 2022 funding line. The project was initiated and supported by the State of Carinthia, in particular the Carinthian Institute for Lake Research.