TY  - JOUR
A1  - Vormoor, Klaus Josef
A1  - Heistermann, Maik
A1  - Bronstert, Axel
A1  - Lawrence, Deborah
T1  - Hydrological model parameter (in)stability
BT  - "crash testing" the HBV model under contrasting flood seasonality conditions
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - This paper investigates the transferability of calibrated HBV model parameters under stable and contrasting conditions in terms of flood seasonality and flood generating processes (FGP) in five Norwegian catchments with mixed snowmelt/rainfall regimes. We apply a series of generalized (differential) split-sample tests using a 6-year moving window over (i) the entire runoff observation periods, and (ii) two subsets of runoff observations distinguished by the seasonal occurrence of annual maximum floods during either spring or autumn. The results indicate a general model performance loss due to the transfer of calibrated parameters to independent validation periods of -5 to -17%, on average. However, there is no indication that contrasting flood seasonality exacerbates performance losses, which contradicts the assumption that optimized parameter sets for snowmelt-dominated floods (during spring) perform particularly poorly on validation periods with rainfall-dominated floods (during autumn) and vice versa.
KW  - hydrological modelling
KW  - flood seasonality
KW  - differential split-sample test
KW  - flood generating processes
KW  - Nordic catchments
Y1  - 2018
U6  - https://doi.org/10.1080/02626667.2018.1466056
SN  - 0262-6667
SN  - 2150-3435
VL  - 63
IS  - 7
SP  - 991
EP  - 1007
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - GEN
A1  - Kormann, Christoph
A1  - Bronstert, Axel
A1  - Francke, Till
A1  - Recknagel, Thomas
A1  - Gräff, Thomas
T1  - Model-Based attribution of high-resolution streamflow trends in two alpine basins of Western Austria
N2  - Several trend studies have shown that hydrological conditions are changing considerably in the Alpine region. However, the reasons for these changes are only partially understood and trend analyses alone are not able to shed much light. Hydrological modelling is one possible way to identify the trend drivers, i.e., to attribute the detected streamflow trends, given that the model captures all important processes causing the trends. We modelled the hydrological conditions for two alpine catchments in western Austria (a large, mostly lower-altitude catchment with wide valley plains and a nested high-altitude, glaciated headwater catchment) with the distributed, physically-oriented WaSiM-ETH model, which includes a dynamical glacier module. The model was calibrated in a transient mode, i.e., not only on several standard goodness measures and glacier extents, but also in such a way that the simulated streamflow trends fit with the observed ones during the investigation period 1980 to 2007. With this approach, it was possible to separate streamflow components, identify the trends of flow components, and study their relation to trends in atmospheric variables. In addition to trends in annual averages, highly resolved trends for each Julian day were derived, since they proved powerful in an earlier, data-based attribution study. We were able to show that annual and highly resolved trends can be modelled sufficiently well. The results provide a holistic, year-round picture of the drivers of alpine streamflow changes: Higher-altitude catchments are strongly affected by earlier firn melt and snowmelt in spring and increased ice melt throughout the ablation season. Changes in lower-altitude areas are mostly caused by earlier and lower snowmelt volumes. All highly resolved trends in streamflow and its components show an explicit similarity to the local temperature trends. Finally, results indicate that evapotranspiration has been increasing in the lower altitudes during the study period.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 364 
KW  - trend attribution
KW  - trend detection
KW  - climate change
KW  - trend drivers
KW  - hydrological modelling
KW  - alpine catchments
KW  - streamflow
KW  - hydroclimatology
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400641
ER  -