Projecting the future levels of Lake Victoria
: A water balance model study

Scriptie/Masterproef: Master's Thesis

Samenvatting

Lake Victoria is the largest lake in Africa and one of the two major sources of the Nile River. The water level of Lake Victoria is determined by its water balance. Consisting of precipitation on the lake, evaporation from the lake, inflow from tributary rivers and lake outflow, controlled by two dams for hydropower, the water balance is controlled by both climatic conditions and human management. Future climate projections reveal a decrease of the precipitation and an increase of the evaporation over Lake Victoria, which has implications for the water balance and resulting lake level. Previous water balance studies of Lake Victoria encompass a lot of limitations, which made it so far impossible to develop projections of future lake levels. Therefore, the main objective of this thesis is to construct a high-quality water balance model that is able to provide projections of future lake levels based on future climate simulations.

A water balance model is constructed based on state-of-the-art satellite observations,a high-resolution reanalysis downscaling and outflow values recorded at the dam. The comparison with observed lake levels revealed that the model is able to closely represent the lake level fluctuations of Lake Victoria. Precipitation on the lake is the main cause of lake level fluctuations, as it experiences the largest seasonal and inter annual variability of all water balance terms. Next,the ability of current-generation regional climate models to provide the input for the constructed water balance model is tested. It is found that they are typically not able to reproduce lake levels, due to the imperfect representation of evaporation and precipitation in the Lake Victoria basin because the mesoscale circulation in the basin is not well resolved. Only one regional climate model (CRCM5) provides a reliable representation of the climatology above the region. Future lake levels are projected for different outflow scenarios using the climate simulations of this regional climate model, following the Representative Concentration Pathway 4.5 (RCP4.5), a stabilization emission scenario. Results indicate that the evolution of future lake levels is determined by both the driving global climate model of the simulation and the outflow scenario. Only the scenario in which outflow is dynamically adjusted based on the lake level to mimic natural outflow provided sustainable lake level projections. This highlights the importance of human outflow strategies at the dam, which will become even more important in the future regarding the need for (hydro-) electricity.

Since only a part of the total spread is sampled by the two water balance model projections and since they account for only one emission scenario, further research is needed to eventually include all regional climate simulations following different emission scenarios in the lake level projections. Nevertheless, in this study, an important step is made towards projecting future water levels of Lake Victoria and accounting for the impact of climate change and management decisions on water resources in this region.
Datum prijsjun 2017
Originele taalEnglish
Prijsuitreikende instantie
  • KU Leuven
  • Vrije Universiteit Brussel
BegeleiderNicole Van Lipzig (Promotor) & Wim Thiery (Promotor)

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