Integrated water resources modeling and its uncertainty analysis for coastal watersheds under climate and land-use change

• Applicant: Professor Dr. Stefan J. Kollet
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 162121866

It has been shown that three-dimensional groundwater dynamics may have strong influence on the mass-and energy balance (MEB) of the landsurface. On the other hand, the landsurface MEB, including processes such as evapotranspiration, plays a key role in groundwater recharge. Therefore, changes in land-use type and patterns may have significant influence on the MEB and groundwater recharge in the future, because evapotranspiration is strongly determined by the vegetation cover. This illustrates the reciprocity in the coupled hydrologic and energy cycles. Without explicit inclusion of groundwater dynamics, MEB calculations are burdened with significant inaccuracies and uncertainties (and vice versa), and may lead to wrong predictions. The goal is to study and quantify the influence of groundwater dynamics on the MEB of the landsurface over large spatial and temporal scales and to derive estimates of groundwater recharge and evapotranspiration influenced by future climate and land-use change. The proposed study will work under the scientific exemplar that the subsurface-landsurface system must be represented in a physically consistent and integrated fashion. This will be achieved by a fusion of theoretical approaches and measured data. An existing integrated, high-performance computing simulation platform for MEB calculations of the subsurface-landsurface system will be improved and applied to the large scale Luanhe watershed in China for validation and prognostic purposes. For the first time, the entire system from the water table across the landsurface will be considered, which will lead to more accurate predictions of the system state. The MEB at the landsurface is governed by complex processes including plant transpiration. Until now, these processes are approximated via ad-hoc empirical approaches that have not been validated adequately using measurements. In this study, a more complete transpiration and root water uptake model will be implemented to account for e.g., variable root density distributions depending on subsurface moisture conditions that are commonly neglected and optimized stomatal resistance parameterizations. These approaches will enter directly into the integrated simulation platform. In a validation exercise, the simulation platform will be applied to the Luanhe watershed. Groundwater recharge - a parameter of major interest in the study region - will be extracted and the influence of climate and land-use change will be investigated. This will include scenario simulations of future climate and landuse changes in the region. As a demonstration, high-resolution, long-term forecasts of the MEB of the Luanhe catchment will be generated. These results will provide the foundation for management and mitigation strategies of potential consequences of climate and land-use change, which is the primary subject of the Chinese research team.

• DFG Programme: Research Grants
• International Connection: China
• Participating Persons: Professor Dr. Clemens Simmer; Professor Dr. Dongxiao Zhang