Passion for Hydrology Drives Unmanned Aerial Vehicle Research

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Ms Nobubelo Ngwenya’s cum laude result for her Master’s in Hydrology is evidence of her passion for the subject that developed during an undergraduate internship which demonstrated the real difference the skills she gained in the classroom could make in people’s lives.

Originally from Bulawayo in Zimbabwe where she completed her undergraduate studies in Civil and Water Engineering at the National University of Science and Technology (NUST).

An undergraduate internship working with a local non-governmental organisation partnering with rural communities to provide clean water from both surface and groundwater sources inspired Ngwenya to take her hydrological studies further. She realised the value of applying hydrological principles to manage water resources, design supply and irrigation systems, and support flood control, seeing how she could integrate water resources management and environmental sustainability.

Attracted to UKZN’s Master’s in Hydrology programme, Ngwenya found herself in a supportive academic environment that encouraged innovation, collaboration and professional growth.

Her research focused on using unmanned aerial vehicle (UAV)-based remote sensing to monitor water quality, specifically chlorophyll-a concentrations, in inland water bodies. UAVs provide high-resolution, cost-effective alternatives to traditional satellite imagery that often lacks the resolution needed for smaller water bodies.

She conducted a global review of UAV applications for monitoring chlorophyll-a and related parameters. In excessive concentrations, this compound can reduce water quality and threaten aquatic ecosystems. She applied the approach to a small agricultural reservoir in the Midmar sub-catchment. UAV imagery was collected alongside water samples, with machine learning models trained on ground data to predict water quality directly from UAV images. This method reduces the need for labour-intensive sampling and provides a flexible, scalable tool for high-resolution monitoring. By demonstrating its effectiveness in smallholder agricultural systems, Ngwenya highlighted how UAV-based remote sensing and machine learning approaches can support sustainable water resource management worldwide in similar environments.

She was interested in observing a seasonal variation in chlorophyll-a, with higher concentrations observed after winter rains and during low water levels, and the weak correlation between chlorophyll-a and nutrient levels, indicating complex nutrient dynamics that require continuous monitoring. She also found higher concentrations near inlets, shallow areas, and the periphery of the reservoir, suggesting that runoff and livestock activities nearby contributed to pollution.

Conducting a study using UAVs required navigating regulatory restrictions, which limited site selection, and was subject to favourable weather conditions, demanding carefully-aligned flight campaigns and a flexible schedule. Ngwenya also had to incorporate ground control points and thorough pre-flight checks to mitigate the UAV’s reduced GPS mapping accuracy.

Starting a family during her master’s studies also provided the impetus to complete her studies on time and inspired pride in Ngwenya as she attained a cum laude result despite this added responsibility.

She plans to go on to a PhD in Civil Engineering, focusing on water resources, while also working to contribute to applied research and practical solutions in water resource management.

Ngwenya thanked God for His guidance while completing her studies, and her supervisors, Dr Tsitsi Bangira and Dr Mbulisi Sibanda, for their support, as well as Dr Shaeden Gokool for UAV assistance.

Her thanks were also extended to Professor Seifu Kebede Gurmessa, Professor Tafadzwanashe Mabhaudhi, and the Water Research Commission for their support, while she was grateful to her colleagues who assisted with field data collection and laboratory staff for their technical contributions.

Finally, she thanked her family, her husband, daughter and parents for their unwavering encouragement.

Words: Christine Cuénod

Photograph: Sethu Dlamini