Long Term Land Use - Precipitation Feedbacks in the Hai River and Poyang Lake Regions
Zusammenfassung der Projektergebnisse
On all scales, the components of the hydrological cycle are continuously changing and affect the availability and quality of water as essential pre‐requisites for human development and sustainable ecological conditions. Climate and land‐use changes are thereby the main drivers for changes in the hydrological cycle. For a correct quantification of past, current and future‐expected water availability, the feedback mechanisms between the atmosphere, the land surface, and the subsurface play a crucial role. The investigation of these feedback mechanisms requires coupled atmospheric‐ hydrological modelling systems. But in particular for meso‐scale catchments these investigations are hampered by the lack of appropriate regional model systems which allow in addition long‐term, climatic relevant analysis. It was therefore the objective to develop and apply a fully two way coupled, meso‐scale regional model system and to investigate long term feedback mechanisms between groundwater‐, soil moisture dynamics and precipitation. Our approach combines the regional atmospheric model WRF‐ARW (Skamarock et al, 2008) with the distributed hydrological model HMS (Yu et al, 2006). We selected these two models because they share the same land surface model, the Noah‐LSM (Chen, Duddhia, 2001) i.e. compatible water and energy flux formulations of state variables and interfaces for the boundary layer, the land surface and subsurface in both models. The computational demand of this coupled model system allows long‐term simulations for climate‐relevant scales of tens of years. In addition, we implemented methods allowing for the interaction between the groundwater and soil moisture states of the LSM. By capillary rise, the groundwater table can affect the moisture content of the upper unsaturated zone and therefore alter the lower boundary conditions for evapotranspiration or infiltration. This upward flux is often not taken into account in LSMs that are typically used with regional climate models. Before the application of the developed fully coupled model system uncoupled simulations of the dynamical regional atmosphere model as well as the hydrological model are required to identify suited setups and calibrate the model for the target region. The first long‐term application of the fully coupled modelling system was performed for the Poyang Lake basin in China which is located in southern China and covers an area of about 160 000 km². For this purpose, the developed model system is applied for the fine nest of a double nest approach with a spatial resolution of 10x10 km² using 123 x 123 grid cells. The simulation results show that the model system is able to simulate the atmospheric and hydrological conditions up to streamflow in the rivers. Furthermore the added‐value, potentials and benefits of the fully coupled atmospheric-hydrological modelling system was demonstrated allowing investigations of the hydrometeorological flux response to climate and land‐use changes at regional scales. Due to the successful development of the fully coupled modelling system we decided to test, apply and validate it further for other basins in different regions and climate zones of the world.
Projektbezogene Publikationen (Auswahl)
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(2012): Coupled atmospheric‐hydrological modeling for feedback investigations in the Poyang lake catchment, China. AGU Fall meeting San Francisco, USA, December 03‐07
Wagner S., Fersch B., Kunstmann H., Yang C., Yuan F., Yu Z.
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(2012): Coupling approaches for groundwater‐soil‐atmosphere interaction in a pre‐Alpine environment. AGU Fall meeting San Francisco, USA, December 03‐07
Fersch B., Wagner S., Rummler T., Gochis D., Kunstmann H.
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(2013): Hydrometeorological modelling for Poyang Lake region, China. IAHS Publ. 359, 152‐157
Wagner S., Fersch B., Kunstmann H., Yuan F., Yang C., Yu Z.
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(2013): Impact of groundwater dynamics and soil‐type on modelling coupled water exchange processes between land and atmosphere. IAHS Publ. 359, 140‐145
Fersch B., Wagner S., Rummler T., Gocchis D., Kunstmann H.
