Design, construction and evaluation of a drone-tethered river survey vessel

As part of the CGIAR Initiative on Digital Innovation, GroundTruth, in partnership with the International Water Management Institute (IWMI), investigated the use of Unmanned Aerial Vehicles (UAVs) to aid in performing bathymetric and water quality surveys. A key outcome of the research and development within this collaboration has been the design and construction of a low-cost survey system comprising a survey vessel equipped with multiple sensors that collect water quality and bathymetric data and can be connected to a UAV. Traditional point-sampling methods limit comprehensive assessments of river health over large spatial areas. This challenge was addressed by developing a drone-towed survey vessel for spatially extensive water quality and depth data collection. The aim of developing the survey vessel was to improve the data collection process which could be useful to further develop the linkages between river flow regimes and water quality parameters.

The vessel that was built was equipped with temperature sensors to capture thermal variations across a section of the river, a Total Dissolved Solids (TDS) sensor to monitor total dissolved solids, a Sound Navigation and Ranging (SoNAR) device to map variations in the riverbed profile, a turbidity sensor to provide a measure of water clarity and a Global Positioning System (GPS) module for precise geotagging of all sensor readings. The system was tested at the Lions River in KwaZulu-Natal, South Africa, and the drone-tethered data collection vessel enabled a safe and efficient survey of a river segment. The system was used to collect high-resolution data related to water quality along a reach of the river. The depth data acquired from the vessel was integrated with Light Detection and Ranging (LiDAR) data to generate detailed bathymetric maps for the site. This highlights the potential for expansion in terms of data collection capabilities compared to traditional point sampling methods.

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