Assessment of the impact of climate change on hydrological safety of dams with gated spillways

Dam breaks can cause important economic and human losses. Usually, design floods are estimated by using a statistical analysis of observed data in the past, though such data are usually short. Moreover, design floods are usually estimated for high return periods. In addition, climate change is expected to increase the frequency and magnitude of floods in the future. A stochastic methodology to assess hydrological dam safety considering climate change is presented. The methodology is applied to the Eugui Dam on the Arga river in the north of Spain. The stochastic model STORAGE is used to simulate long time series of precipitation. Precipitation projections of 12 climate models, three periods and two emission scenarios are used to consider climate change in the STORAGE model. The precipitation time series generated stochastically are transformed into runoff time series by using the continuous COSMO4SUB hydrological model that uses a high-resolution digital terrain model, soil type data, and the precipitation supplied by the STORAGE model as input data. It provides continuous runoff time series as output from which annual maximum hydrographs are extracted. Time series of annual maximum hydrographs are considered as inflow hydrographs to the reservoir. The Volume Evaluation Method is applied to simulate the operation of spillway gates, obtaining maximum water levels in the reservoir and outflow hydrographs. Therefore, the methodology proposed allows practitioners and dam owners to check the hydrological dam safety requirements detailed in the regulations, accounting for climate change.