Technical Reports WATCH Technical Report Number 22: The WATCH forcing data 1958-2001: a meteorological forcing dataset for land surface- and hydrological-models New global sub-daily meteorological forcing data are provided for use with landsurface-and hydrological-models. The data are derived from the ERA-40 reanalysis product via sequential interpolation to half-degree resolution, elevation correction and monthly-scale adjustments based on CRU (corrected-temperature, diurnal temperature range, cloud-cover) and GPCC (precipitation) monthly observations combined with new corrections for varying atmospheric aerosol-loading and separate precipitation gauge corrections for rainfall and snowfall. Weedon, G.P., Gomes, S., Viterbo, P., Österle, H., Adam, J.C., Bellouin, N.,Boucher, O., and Best, M., February 26, 2010 -
WATCH Technical Report Number 20: Hydrological drought characteristics of the Nedožery sub catchment, Upper Nitra, Slovakia, based on HBV modelling A River Basin Hydrological Model (RBHM) using HBV has been developed for the Nedožery catchment, Upper Nitra (Slovakia), which is a a focal area in the WATCH Test Basin Upper-Nitra (Slovakia). The hydrological regime of the Nedožery catchment is affected by snow, in particular in the headwaters. It is a fast-responding catchment (crystalline rocks). The model has been tested against time series of observed river flow, groundwater levels and snow. Trend analysis on the model input data showed downward trends in the observed discharge and upward trends in the observed precipitation and the annual number of snow days, which resulted in an over- (1974-1990) and underestimation (1991-2006) of the observed discharge. Time series of observations and outcome from the models were used to identify different drought types (meteorological drought, hydrological drought). Hydrological droughts (both winter and summer) in Nedožery catchment develop due to above average temperatures combined with below average precipitation. In winter this leads to a below average snow cover (resulting in lower spring discharges) and the occurrence of above average evapotranspiration. In winter, hydrological drought can also be caused by below average temperature, because water is stored on the surface as snow for a longer period. Such a winter drought does not continue into summer, because it ends by above average snowmelt in spring. HBV’s results were compared with outcome from the lumped, conceptual hydrological model BILAN and the distributed, physically-based hydrological model FRIER to test the impact of model structure on drought assessment. The BILAN model gives a lower number of droughts which are longer as compared with HBV. Recession curves simulated with BILAN are long and response on precipitation events during the recession is almost invisible. FRIER output shows more, but shorter droughts which indicates FRIER reacts faster to precipitation than HBV and BILAN. The RBHM and the outcome will be used in the WATCH project: (1) to develop a generic method for drought propagation, (2) to test the usefulness of large-scale forcing data (WATCH Forcing Dataset), and (3) to test the ability of large-scale land surface models (LSHMs) and global hydrological models (GHMs) to capture droughts. Jacob Oosterwijk, Anne F. van Loon, Andrej Machlica, Oliver Horvát, Henny A.J. van Lanen & Miriam Fendeková, December 28, 2009 WATCH Technical Report Number 19: Drought analysis for the Upper-Metuje and Upper-Sázava catchments (Czech Republic) using the hydrological model HBV River Basin Hydrological Models (RBHMs) using HBV have been developed for the Upper-Metuje and the Upper-Sázava catchments, which are focal areas in the WATCH Test Basin Upper-Elbe (Czech Republic). Both catchments have been selected for their contrasting hydrogeology, i.e. the Upper-Metuje catchment is a more slowly-responding catchment (sandstones), whereas the Upper-Sázava catchment is fast-responding catchment (crystalline rocks). The models have been tested against time series of observed river flow and groundwater levels. Time series of observations and outcome from the models have been used to identify different drought types (meteorological drought, hydrological drought). The RBHM for the Upper-Metuje catchment performs rather well. In the period 1982-2006 about 100 streamflow droughts were identified. This is slightly less than the number of droughts in the precipitation, but significantly more than the number of droughts in groundwater. The RBHM for the Upper-Sázava catchment performs less, because of monitoring of water abstractions and sewage water releases at a too low temporal resolution. The RBHMs and the outcome will be used in the WATCH project: (1) to develop a generic method for drought propagation, (2) to test the usefulness of large-scale forcing data (WATCH Forcing Dataset), and (3) to test the ability of large-scale land surface models (LSHMs) and global hydrological models (GHMs) to capture droughts. Oldrich Rakovec, Anne F. van Loon, Stanislav Horacek, Ladislav Kasparek, Henny A.J. van Lanen & Oldrich Novicky, September 16, 2009 -
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