Department Surface Waters - Research and Management


How are dams changing water quality in tropical African rivers?

Photo: Simon Spratley, ATEC3D

The fast growing African population triggers a rising demand of water, food and energy. Such needs lead to major anthropogenic pressures on African River systems. Among others, the ongoing boom of dam constructions will affect river water quantity and quality.
In my current Ph.D. project, we investigate the Zambezi River – Kariba Dam system: this case study can help to shed some light on the water quality alteration by large dams in tropical regions. In particular, we characterize Kariba Lake’s internal stratification dynamics to understand how this man-made lentic system plays a major role for the downstream Zambezi River’s thermal and oxygen regimes. Moreover, through a modelling approach, we assessed and quantified the thermal and oxygen alteration in the Zambezi River downstream the reservoir. Scenario calculations indicate a large potential for mitigating downstream water quality alterations by implementing a hypothetical selective withdrawal technology. However, we show that a different and cooperative management of the existing infrastructure of Kariba Dam has the potential to mitigate most of the actual water quality alterations. Finally, we carried out a one-year water quality monitoring campaign across the Zambezi River Basin to deepen our understanding about the relationship between lake dynamics, dam management and river water quality alterations. Ultimately, we aim to assess the degree of reversibility of the main downstream alterations (temperature, oxygen, CO2, pH, …) and consequently the quantification of their longitudinal extent.

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Calamita, E.; Schmid, M.; Kunz, M.; Ndebele-Murisa, M. R.; Magadza, C. H. D.; Nyambe, I.; Wehrli, B. (2019) Sixty years since the creation of Lake Kariba: thermal and oxygen dynamics in the riverine and lacustrine sub-basins, PLoS One, 14(11), e0224679 (21 pp.), doi:10.1371/journal.pone.0224679, Institutional Repository
Winton, R. S.; Calamita, E.; Wehrli, B. (2019) Reviews and syntheses: dams, water quality and tropical reservoir stratification, Biogeosciences, 16(8), 1657-1671, doi:10.5194/bg-16-1657-2019, Institutional Repository

Soft Publications