Stochastic water balance simulation for Lake Balaton (Hungary) under climatic pressure

Lake Balaton--due to its remarkable shallowness--is deemed to be sensitive to climatic variations. Historical records suggest, that the water level naturally fluctuated within significantly broader boundaries than the present regulation interval. We made a detailed, dynamic water balance simulations relying on a watershed model and two climatic scenarios. A periodic ARMA model simulated the natural water balance of the lake. The results confirmed, that the lake is not endangered under the expected climate changes. The probability of low levels may increase in the future by up to an order of magnitude. Uneven distribution and increased deviation of precipitation was found to be an important climatic factor from the aspect of low waters. A sensitivity analysis showed, that the sensitivity of the lake increases with the amplitude of climate change. The parameter uncertainty analysis revealed, that even with so long history of observations, the uncertainty of statistical estimates has larger effect than the anticipated climate change. Unfortunately, the time horizon of climate change is not far enough to make up for the necessary data collection, so possible interventions must dispense with a sound scientific justification.