Basically, it was an important personal development for me. A doctoral thesis is simply a 360-degree experience that moves you forwards in many areas, for example in terms of self-confidence.
Both the interdisciplinary character of the project and the multicultural environment were exciting challenges. We had to find a common vocabulary among scientists with different backgrounds and the right way to communicate among different project partners.
Doing fieldwork in Africa was a completely new experience for me and being in the Zambezi River’s water was very exciting. During our river sampling I discovered a real fear of animals. In Zambia I experienced my first encounter with an elephant; he chased us in our car – that was scary. Then a crocodile tried to eat our instrument and he managed to break it; that was very frightening.
What are the most important results of your doctoral thesis?
With my doctoral thesis, I was able to show that there are two processes due to river damming that influence water quality: the deposition of sediments and nutrients and the thermal stratification in the reservoirs. Stratification occurs in most, if not all, large low-latitude reservoirs on at least a seasonal basis. Among other things, this leads to changes in water temperature and oxygen content in the reservoir water, which in turn affects the river ecosystems downstream.
For the sustainable management of a dam, it is therefore important to analyse the condition of the reservoirs in detail. In the case of the Kariba Dam, the largest artificial reservoir in the world by volume, the cooperation between the two countries, Zambia and Zimbabwe, whose border runs exactly through the middle of the dam, could potentially mitigate the actual downstream water quality alterations. These results reveal that transboundary dams may offer additional opportunities for optimised management.
Moreover, we assessed the carbon budget of the Kariba Reservoir and we found that the atmospheric CO2 emissions from the Zambezi River surface downstream of Kariba fluctuate strongly over different timescales, and failing to account for these fluctuations could lead to errors in the carbon budgeting of the hydroelectric reservoir. (See Eawag News of 14 June 2021: “When hydropower plants emit carbon dioxide”.)
Are the findings being implemented at the Kariba Dam today?
Not yet in practice, as far as I know. But the results are being discussed, as they are struggling with some water problems on the Zambezi, for example droughts and declining fish abundance. But the question of how to manage the dams without destroying the environment downstream is also on the minds of the authorities and operators. I hope that my research results can be a little puzzle piece that may help the sustainable management of the wonderful Zambezi River.