The waters that feed the Nyamwamba River in western Uganda start as meltwater from the glaciers high up in the Rwenzori Mountains. A small scale run-of-river hydropower plant, equipped with a low height tyrolean type intake weir, is now operating just upstream of the town of Kilembe, the first large community along this river. History has seen floods cause realignments of the river through the town and major damage to property and loss of life.
A devastating flood occurred during the design phase for the scheme prior to any construction commencing, which caused loss of life and significant damage to roads, bridges and buildings within the town, including the hospital. Design changes to improve resilience of all riverine connections were made, including relocation of the diversion weir to a stronghold point within the basic protection zone of a natural island. A flood diversion dyke was constructed across one of the river branches that flows around the island, with its alignment, type and height optimised to capture low flows for energy generation while deflecting large flows away from the weir to mitigate flood damage.
Another major flood arrived three months after completion. No damage was sustained which provided confidence in the resilience of the headworks. A major river dredging program contributed to the overall resilience of this reach of river through the town.
This paper describes the challenges for the development of the project site in terms of physical considerations to work with the river, adopting some lessons learned from the pre-construction floods.
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ANCOLD is an incorporated voluntary association of organisations and individual professionals with an interest in dams in Australia.