The sharp rise in the level of Lake Victoria between 1961 and 1964 has been found difficult to explain in terms of the components of the water balance. After reviewing lake inflows and the method of calculating lake rainfall from lakeside gauges, the historic lake water balance has been reproduced. The rise in lake level can be explained through rainfall and resulting tributary inflows, which would allow projections of possible future levels to be made by analysis of rainfall series. Bilan hydrologique du Lac Victoria RESUME L'élévation sensible du niveau du Lac Victoria enregistrée entre 1961 et 1964 était restée difficile à expliquer en terme de bilan hydrologique. Après révision des débits arrivant dans le lac et de la méthode de calcul des précipitations sur l'étendue du lac, un modèle historique a pu être reproduit. L'élévation du niveau du lac peut alors être expliquée par la combinaison des précipitations et de l'effet résultant des débits des tributaires. Les évolutions futures du niveau du lac pourraient être prévues par l'analyse des séries de précipitations.

Resilient water supplies in England need to be secured in the face of challenges of population growth, climate change and environmental sustainability. We propose a blueprint for water resources planning that uses system simulation modelling to estimate the frequency, duration and severity of water shortages at present and in the context of future plans and scenarios. We use multiobjective optimisation tools to explore trade‐offs between these risk metrics and cost of alternative plans, and we use sensitivity analysis to identify plans that robustly achieve targets for tolerable risk, alongside other performance objectives. The results of a case study in the Thames basin demonstrate that the proposed methodology is feasible given commonly available data sets and models. The proposed method provides evidence with which to develop water resource management plans that demonstrably balance the risks of water shortages, costs to water users and environmental constraints in an uncertain future.

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9Lake Malawi is the third largest lake in Africa and plays an important role in water 10 supply, hydropower generation, agriculture and fisheries in the region. Lake level

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