Impact analysis of climate change for an Alpine catchment using high resolution dynamic downscaling of ECHAM4 time slices

International audienceGlobal climate change affects spatial and temporal patterns of precipitation and so has a major impact on surface and subsurface water balances. While global climate models are designed to describe climate change on global or continental scales, their resolution is too coarse for them to be suitable for describing regional climate change. Therefore, regional climate models are applied to downscale the coarse meteorological fields to a much higher spatial resolution to take account of regional climate phenomena. The changes of atmospheric state due to regional climate change must be translated into surface and sub-surface water fluxes so that the impact on water balances in specific catchments can be investigated. This can be achieved by the coupled regional climatic/hydrological simulations presented here. The non-hydrostatic regional climate model MCCM was used for dynamic downscaling for two time slices of a global climate model simulation with the GCM ECHAM4 (IPCC scenario IS92a, "business as usual") from 2.8° × 2.8° to 4 × 4 km2 resolution for the years 1991?1999 and 2031?2039. This allowed derivation of detailed maps showing changes in precipitation and temperature in a region of southern Germany and the central Alps. The performance of the downscaled ECHAM4 to reproduce the seasonality of precipitation in central Europe for the recent climate was investigated by comparison with dynamically downscaled ECMWF reanalyses in 20 × 20 km2 resolution. The downscaled ECHAM4 fields underestimate precipitation significantly in summer. The ratio of mean monthly downscaled ECHAM4 and ECMWF precipitation showed little variation, so it was used to adjust the course of precipitation for the ECHAM4/MCCM fields before it was applied in the hydrological model. The high resolution meteorological fields were aggregated to 8-hour time steps and applied to the distributed hydrological model WaSiM to simulate the water balance of the alpine catchment of the river Ammer (c. 700 km2) at 100 × 100 m2 resolution. To check the reliability of the coupled regional climatic/hydrological simulation results for the recent climate, they were compared with those of a station-based hydrological simulation for the period 1991?1999. This study shows the changes in the temperature and precipitation distributions in the catchment from the recent climate to the future climate scenario and how these will affect the frequency distribution of runoff. Keywords: coupled climate-hydrology simulations, dynamic downscaling, distributed hydrological modelling, ECHAM4 climate scenario, alpine hydrolog

Developing a presence in Southeast Asia -an inter-cultural challenge for medium-sized comapanies

European publications provide very little coverage of the current business activities of medium-sized companies in Southeast Asia. In Europe generally, far too little is known about the Asia-Pacific region of which Southeast Asia forms part. In particular, there is little awareness of the business opportunities and risks in this part of the world, not only in the short term but also - and more importantly - in the medium and long term. The impact on the Asian region of the events which took place in New York on September 11, 2001 will not be investigated here. It will be some time yet before their consequences can be properly assessed

Physically based distributed hydrological modelling of the Upper Jordan catchment and investigation of effective model equations

International audienceSufficient freshwater availability in the water scarce environment of the Upper Jordan Catchment (UJC) is a central prerequisite for peaceful agricultural and industrial development. Hydrological modelling is required to understand terrestrial water balance and to provide scientifically sound estimates on water availability. This article aims at two related objectives: First the water balance of the UJC, a hydrogeologically complex catchment located at the borders of Israel, Syria and the Lebanon, is investigated. It is for the first time that a physically based model is set up for this region that accounts both for the entire terrestrial water balance and in particular for the groundwater-surface water interaction. It is shown that the model is able to describe observed river discharges satisfactorily. Secondly, it is investigated if observed and simulated runoff components can be explained by simple lumped approaches based on 1) linear filter theory and 2) neural networks and what the number of degrees of freedom for the runoff components is. It is exemplary shown for the Ayun subcatchment of the UJC that the simulated river discharge, the direct runoff component and the interflow runoff component as modelled by the physically based distributed hydrological model WaSiM can be described by simple effective equations with only 3 to 5 degrees of freedom. Application of simple lumped approaches to observed river discharge values showed much weaker performance

Model based distributed water balance monitoring of the White Volta catchment in West Africa through coupled meteorological-hydrological simulations

Sustainable water management requires the quantification of the spatial and temporal changes of water balance variables. Fully distributed hydrological simulations of these variables are especially in regions with weak infrastructure challenging, because the required meteorological input data are often not available in a sufficient spatial and temporal resolution. One possibility to deal with this limitation is to provide the required input data with a meteorological model. This combination results in a one way meteorological-hydrological coupling system. Within the framework of the GLOWA-Volta project it is investigated to what extent meteorological models are able to provide the required meteorological fields with sufficient accuracy for the hydrological modeling. For this study the mesoscale meteorological model MM5 and the fully distributed water balance simulation model WaSiM-ETH were first adapted and validated separately. The research area is the White Volta catchment in the semi-arid to sub-humid climate zone in West Africa. The meteorological simulations tend toward overestimating measured precipitation sums. The coupled meteorological-hydrological runoff simulations show similar model performances as the simulations driven by observations indicating the potential of this system for a contemporary estimation of the terrestrial water balance