Abstract
Regional coupled system models require a high-resolution discharge component to couple their atmosphere/land components to the ocean component and to adequately resolve smaller catchments and the day-to-day variability of discharge. As the currently coupled discharge models usually do not fulfill this requirement, we improved a well-established discharge model, the HD model, to be globally applicable at 5 Min. resolution to prepare high-resolution discharge simulations over Europe and the Baltic Sea catchment. Here, no river specific parameter adjustments were conducted so that the model is generally applicable for climate change studies and over ungauged catchments. For the validation of the 5 Min. HD (HD5) model, we drive it with prescribed fields of surface and subsurface runoff. As no large-scale observations of these variables exist, they need to be calculated by a land surface scheme or hydrology model using observed or re-analyzed meteorological data. In order to pay regard to uncertainties introduced by these calculations, three different methods and datasets were used to derive the required fields of surface and subsurface runoff for the forcing of the HD5 model. 10-years simulations (2000-2009) show that for many European rivers, where daily discharge observations were available for comparison, the HD5 model captures the main discharge peaks reasonably well. As direct anthropogenic impact on the discharge, such as by regulation or dams, is not regarded in the HD model, those effects generally cannot be simulated. Thus, discharges for many heavily regulated rivers in Scandinavia or for the rivers Volga and Don are not well represented by the model. The comparison of the simulated discharges obtained indicates that the HD5 model is suitable to evaluate the terrestrial hydrological cycle of climate models or land surface models, especially with regard to the separation of throughfall (rain or snow melt) into surface and subsurface runoff.
Highlights
The hydrological cycle is crucially important to life on Earth since water is essential nourishment for all organisms
As the first coupled high-resolution discharge simulations are planned over Europe and the Baltic Sea catchment, we focus on the respective regions in the present study
As the HD5 model shall be applied in climate change studies and over ungauged catchments, no river specific parameter adjustments, e.g., by calibration, were conducted
Summary
The hydrological cycle is crucially important to life on Earth since water is essential nourishment for all organisms. Large irrigation activities in many parts of Middle Asia led to man-made climate change in the Aral Sea region that were caused by the lake’s catastrophic desiccation within the last five decades (Breckle and Geldyeva, 2012). This had severe consequences for the societies living in this area. Another example is the prominent drought period in the Sahel that began at the end of the 1960s and ended in the mid-1980s (Anyamba and Tucker, 2005). This caused a noticeable decline of per capita food production and food self-sufficiency ratios in the Sahel (Epule et al, 2014)
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