Climate Change Impacts on River Catchment Hydrology Using Dynamic Downscaling of Global Climate Models

Abstract

Impacts from climate change may affect vital factors of environmental and human security related to water uses, such as domestic water supply, hydropower and industrial production, agricultural irrigation and ecosystems needs. This is particularly important in regions with arid and semi-arid climates like the Mediterranean and the South Eastern Europe. In this presentation the coupling of different climate change models with a distributed hydrological model was developed in order to explore the impact of climate change on water resources at the river basin level. Firstly, the coupled atmosphere-ocean global climate model ECHAM5/MPIOM, developed by the Max Planck Institute for Meteorology in Hamburg, Germany, was used to provide boundary conditions of the regional climate model CLM. Simulation results at 6 hourly intervals were provided for Europe, using a spatial grid resolution of 20 × 20 km. Secondly, the spatially distributed hydrological model MODSUR-NEIGE (MODélisation des transferts de SURface en présence de NEIGE, in French), developed by the School of Mines, Paris, France, was used for dynamically downscaling boundary conditions provided by CLM over a spatially variable grid ranging between 250 m and 2 km in size. In this way temperature, precipitation and evapotranspiration distributions were adapted to local conditions, such as the river watershed relief, local geology and land uses. The methodology is illustrated for the Mesta/Nestos river basin, which is shared between Bulgaria and Greece and is part of the worldwide UNESCO-HELP initiative. The upstream northern part of the basin (Mesta) is in Bulgaria, and the downstream part (Nestos) is in Greece. Impacts from climate change have resulted in a significant reduction of river flow with serious consequences for hydropower production and agricultural activities mainly near the Nestos delta.