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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2018-160
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Modelling the water balance of Lake Victoria (East Africa), part 2: future projections
Inne Vanderkelen1, Nicole P. M. van Lipzig2, and Wim Thiery1,3 1Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Brussels, Belgium
2Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
3Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Abstract. Lake Victoria, the second largest freshwater lake in the world, is one of the major sources of the Nile River. The outlet to the Nile is controlled by two hydropower dams of which the allowed discharge is dictated by the Agreed Curve, an equation relating outflow to lake level. Some regional climate models project a decrease of precipitation and an increase of evaporation over Lake Victoria, with potential important implications for its water balance and resulting level. Yet, nothing is known about the potential consequences of climate change for the water balance of Lake Victoria. In this second part of a two-paper series, we feed a new water balance model for Lake Victoria presented in the first part with climate simulations available through the Coordinated Regional Climate Downscaling Experiment (CORDEX) Africa framework. Our results reveal that most regional climate models are not capable of giving a realistic representation of the water balance of Lake Victoria. Therefore we applied two bias correction methods, resulting in both cases in a closed water balance. Our results reveal that for two emission scenarios (RCP4.5 and 8.5), the decrease in precipitation over the lake and an increase in evaporation are compensated by an increase in basin precipitation leading to more inflow. The future lake level projections show that the outflow scenario and not the emission scenario is the main controlling factor of the future water level evolution. Moreover, inter-model uncertainties are larger than emission scenario uncertainties. The comparison of four different outflow scenarios for the future uncovers that the only sustainable outflow scenario is regulating outflow following the Agreed Curve. The associated outflow encompasses however large uncertainties ranging up to 177 %, which are important to take into account regarding future hydropower generation and water availability downstream.
Citation: Vanderkelen, I., van Lipzig, N. P. M., and Thiery, W.: Modelling the water balance of Lake Victoria (East Africa), part 2: future projections, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2018-160, in review, 2018.
Inne Vanderkelen et al.
Inne Vanderkelen et al.
Inne Vanderkelen et al.

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Short summary
Lake Victoria is the second largest freshwater lake in the world and one of the major sources of the Nile River, which is controlled by two hydropower dams. In this paper we estimate the potential consequences of climate change for future water level fluctuations of Lake Victoria. Our results reveal that the operating strategies at the dam are the main controlling factors of future lake levels and that regional climate simulations used in the projections encompass large uncertainties.
Lake Victoria is the second largest freshwater lake in the world and one of the major sources of...
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