Hydroclimatic and flood inundation modelling of Lake Victoria using the LaVIWaB model

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Study region The Lake Victoria Basin has experienced increasing shoreline flooding in recent decades due to interactions among hydroclimatic variability, land use change, and regulated outflows at the Nalubaale–Kiira (Owen Falls) dam complex. Rising lake levels and extreme rainfall events have intensified flood risks for low-lying littoral communities across East Africa. These trends highlight the need for basin-scale hydrological modelling to better understand lake dynamics and shoreline flooding. Study focus This study develops the Lake Victoria Integrated Water Balance (LaVIWaB) Model, a physically based framework designed to simulate lake level dynamics and flood inundation under varying climatic conditions. The model integrates multi-decadal observations (1984–2023) of precipitation, evaporation, river inflows, regulated outflows, and lake bathymetry using satellite-derived and in-situ datasets. Model calibration shows strong performance in reproducing observed lake levels (NSE = 0.749, R² = 0.749, RMSE = 0.262 m). Validation against satellite-derived lake surface area datasets and high-resolution DEM products shows moderate agreement in capturing lake extent variability (Cor = 0.598, RMSE = 22.77 km²). New hydrological insights for the region The model reproduces seasonal and interannual variability in lake storage and better constrains the nonlinear lake level–area relationship. Once lake levels exceed ∼1132 m a.s.l., small increases trigger disproportionate expansion of inundated areas across low-gradient littoral floodplains, highlighting escalating flood risks and the value of integrated water balance–inundation modelling for regional flood management.