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Institut für Wasser- und Umweltsystemmodellierung - IWS

Abstract

 
   

"Groundwater water resources management models as a part of an integrative decision support system on the river basin scale"

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GLOWA-Danube aims at the development of innovative techniques, scenarios and strategies to investigate the impacts of Global Change on the hydrological cycle within the catchment area of the Upper Danube Basin (Gauge Passau, 77.000 km2). A prototype of the network-based decision support tool ‘DANUBIA’, comprised of 15 fully coupled disciplinary models, has been developed and is currently being validated. The research group ‘Groundwater and Water Management” at the Institute of Hydraulic Engineering of the Universitaet Stuttgart contributes two models to DANUBIA: A groundwater flow and nitrate transport model, and a water supply and distribution model. This paper introduces the DANUBIA objects ‘Groundwater” and ‘WaterSupply” and summarizes the aims, approaches, solutions, and results of the GLOWA-Danube project from the viewpoint of these DANUBIA elements. The crucial aspects of multidisciplinary modeling are exemplified on the basis of typical problems related to the modeling of groundwater and water supply that were identified over three years of collaborative research. The model ‘Groundwater” uses a finite difference approach (MODFLOW). Only regional aquifers with an almost basin-wide occurrence are considered due to restrictions in the availability of data, the common DANUBIA model grid size (1km2), and requirements of the MODFLOW approach. On the physical side, the groundwater model has interfaces to a soil water and a surface water model, which provide parameters that are used as boundary conditions. The model ‘WaterSupply” acts as a link between the various physical models determining water quality and availability on the one hand, and the socio-economic models determining water demand on the other. Its aim is not only to be able to simulate the present day system of water extraction, treatment and distribution, but also its development and change with time. In the Upper Danube Basin, groundwater is the dominant source of drinking and process water (95% in the domestic, 80% in the industrial sector). Therefore, groundwater related processes ranging from recharge, surface water in- and exfiltration, nitrogen leaching and transport, and extraction from wells for domestic, agricultural, and industrial purposes play an important role in both the physical and the socioeconomic parts of the hydrogeological cycle. It is evident that none of the corresponding processes should be treated independently, nor should they be represented in an over-simplified manner. Integrative modeling, however, is a challenging and demanding task. In addition to well known (technical) problems of coupled modeling, certain previously partly neglected aspects of groundwater management pose interesting challenges that are crucial in successful integrative water resources modeling. Such challenges are, for example, the difficulties in calibrating three strictly interdependent models (simulating saturated zone, unsaturated zone, surface water processes), and feedback problems between water demand, water resources, and water supply. This contribution points out problems and challenges of integrative modelling that have been identified by our group in the process chain from the land surface through the saturated zone to the consumers in the domestic, agricultural and industrial field.