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Petzenkirchen, Austria

Wang S.,North China Electrical Power University | Zhang Z.,Beijing Forestry University | Sun G.,U.S. Department of Agriculture | Strauss P.,Federal Agency for Water Management | And 3 more authors.
Hydrology and Earth System Sciences

Model calibration is essential for hydrologic modeling of large watersheds in a heterogeneous mountain environment. Little guidance is available for model calibration protocols for distributed models that aim at capturing the spatial variability of hydrologic processes. This study used the physically-based distributed hydrologic model, MIKE SHE, to contrast a lumped calibration protocol that used streamflow measured at one single watershed outlet to a multi-site calibration method which employed streamflow measurements at three stations within the large Chaohe River basin in northern China. Simulation results showed that the single-site calibrated model was able to sufficiently simulate the hydrographs for two of the three stations (Nash-Sutcliffe coefficient of 0.65-0.75, and correlation coefficient 0.81-0.87 during the testing period), but the model performed poorly for the third station (Nash-Sutcliffe coefficient only 0.44). Sensitivity analysis suggested that streamflow of upstream area of the watershed was dominated by slow groundwater, whilst streamflow of middle- and down- stream areas by relatively quick interflow. Therefore, a multi-site calibration protocol was deemed necessary. Due to the potential errors and uncertainties with respect to the representation of spatial variability, performance measures from the multi-site calibration protocol slightly decreased for two of the three stations, whereas it was improved greatly for the third station. We concluded that multi-site calibration protocol reached a compromise in term of model performance for the three stations, reasonably representing the hydrographs of all three stations with Nash-Sutcliffe coefficient ranging from 0.59-072. The multi-site calibration protocol applied in the analysis generally has advantages to the single site calibration protocol. © Author(s) 2012. Source

Hosl R.,Federal Agency for Water Management | Strauss P.,Federal Agency for Water Management | Glade T.,University of Vienna
Landscape and Urban Planning

A vegetated filter strip (VFS) gains the best retention potential when surface runoff enters the strip as sheet runoff. However, surface runoff convergence may take place in linear flow structures long before approaching the river system. Limited information is available about the extent of these linear flow pathways and the factors that may influence their occurrence in the landscape. To better understand these effects, we carried out detailed field surveys in ten small headwater catchments in different climatic regions in Austria. Ditches and channels directly connected to the stream network were mapped. Surface flow pathways were calculated either with or without integrating the mapped structures. Effective placement of retention structures may also be influenced by the accuracy of digital elevation model (DEM) resolution. We therefore used three different DEMs with varying resolution. The catchment areas connected directly to the stream network via linear drainage structures were identified. In seven out of the ten catchments such unprotected areas (UA) were found. Their extent varied between 10% and 38% of the total catchment area. Factors influencing the extent of UA were length of the road network and annual precipitation. Without integrating the mapped linear structures, UA could not be detected in the broad-gridded DEMs. After integration of mapped linear structures, DEM resolution did not influence the calculated extent of UA. For our environmental setting, GIS-based design of placement of retention structures leads to considerable errors and should be verified by fieldwork. © 2011. Source

Zitek A.,University of Natural Resources and Life Sciences, Vienna | Irrgeher J.,University of Natural Resources and Life Sciences, Vienna | Kletzl M.,Federal Agency for Water Management | Weismann T.,Federal Agency for Water Management | Prohaska T.,University of Natural Resources and Life Sciences, Vienna
Fisheries Management and Ecology

The maternal transmission of a naturally occurring and non-toxic minor isotope of strontium (84Sr) to the central otolith region of the progeny of a typical European freshwater fish species, brown trout, Salmo trutta f.f. L. was accomplished. The focus was to apply minimum doses of a non-toxic solution at physiological salt concentration to minimise potential adverse effects on the fish. Female spawners were intraperitoneally injected with doses of 12.5 and 30.2 μg 84Sr kg-1 fish. Eggs were stripped and the resulting progeny were reared in a hatchery for about 1 year before sampling the otoliths. Strontium isotope ratios in the otoliths of the offspring were measured by cross-sectional line scans using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). Otolith cores of marked juveniles showed a significantly elevated 84Sr/86Sr ratio compared with control fish and to otolith regions created after hatching. Mass marking of cohorts of progeny from individually spiked brown trout with Sr isotopes is therefore possible for dispersal and migration studies without the necessity of handling eggs and applying other larval marking methods like immersion. © 2013 John Wiley & Sons Ltd. Source

Bauer T.,Federal Agency for Water Management | Strauss P.,Federal Agency for Water Management

Estimation of soil cover by residues and vegetation is a fundamental issue for many agriculture-related topics, especially topics dealing with mulching practices and soil erosion, because the amount of cover is a basic driver for erosion risk. Soil cover measurement in the field is very time consuming and subjective. Our ambition for this study was to develop a quick and easy-to-handle field method for calculating the amount of different soil cover types, i.e. simultaneously dead and living biomass, in a single-step analysis. We used an object-based image analysis methodology (OBIA) to quantify different cover types. Classification of the images used resulted in the following classes: residues, vegetation, stones, shadow and uncertainty. The shadow and uncertainty classes were used as an image quality parameter.We compared this method to manual image analysis for the range of between 0 and 50% total cover and different catch crops and winter crops. To increase the accuracy of manual analysis, it was necessary to repeat the assessment five times per image. Degree of agreement between the OBIA method and manual assessment for each of the three different cover types was in the region of 0.8 (r2=0.78 for total cover, r2=0.75 for residue cover, r2=0.82 for vegetation cover). Slopes of the regression intercepts between manual and automated analyses were not different from 1 for total cover and vegetation cover. 95% confidence intervals for the regression lines indicate that confidence limits at total soil cover of 25% (the mean of the investigated range of soil cover) are similar for both the manual evaluation (CI95%=2.8) and the OBIA method (CI95%=3.1). The time needed for evaluation was calculated at 115min per manual image classification and 15min per automated image classification, which we regard as a major advantage of the OBIA methodology. Finally we suggest that, while similar accuracies of evaluation for both methods have been obtained, the OBIA method allows greater objectivity because of predefined classification algorithms and thus the possibility of back tracing results. © 2013 Elsevier B.V. Source

Hosl R.,Federal Agency for Water Management | Strauss P.,Federal Agency for Water Management

If it comes to the advantages of conservation tillage practices, a considerable amount of evidence supports positive effects towards reduction of surface runoff and soil erosion. However studies concerning arable land frequently are conducted under ideal laboratory conditions or "controlled" field conditions, meaning that the experimental approaches were not managed by farmers in the way they usually perform conservation tillage but managed towards an optimisation of the tested features. In addition, applicability of different existing conservation tillage techniques such as no tillage or mulching may be regionally different. The alpine forelands of Central Europe are dominated by small scale farming systems which frequently have limited access to special machinery which is needed to successfully implement no tillage treatments. We therefore carried out rainfall simulation experiments employing conservation tillage practices to test the effectiveness of actual real life conservation tillage methods under conditions prevailing in the alpine forelands of Central Europe. Experiments were carried out in the years 2011 and 2012 for testing the relative performance of different mulching and no tillage treatments on surface runoff and erosion. The tested treatments for the year 2011 were a) no tillage with prior rough seedbed (NT1), b) no tillage with prior fine seedbed (NT2), c) mulching with rotary harrow (M1), d) mulching with rotary harrow and disc harrow (M2) and e) conventional tillage (CT11). The tested treatments for the year 2012 were a) combined mulching (MC), b) mulching with loosened wheel tracks (M. - T), c) mulching without loosened wheel tracks (M+T) and d) conventional tillage (CT12). In 2011, total surface runoff and total soil loss for the different treatments were ordered as follows: NT1. <. NT2. <. CT11. <. M1. <. M2. No significant differences for total soil loss could be identified. For total surface runoff differences were significant (p. <. 0.05) between all treatments, except for NT2 and CT11. The treatments also differed with respect to runoff initiation, sediment concentrations and shear stress. As a main reason for the unexpected bad performance of the mulching treatments M1 and M2 lack of sufficient soil cover (M1: 6%, M2: 11%) together with shallow surface cultivation were identified. In 2012, total surface runoff and total soil loss for the different treatments were ordered as follows: MC. <. M. - T. <. CT12. <. M+T. Although there were a visible trend in these results, significant differences could only be observed for total surface runoff between treatments MC and M+T (p. <. 0.05). We attribute the good performance of treatment MC to the improved soil cover (25%). Wheel tracks of treatment M+T obviously had influenced soil erosion and surface runoff. Under real life conditions of agricultural conservation practices in small scale farming systems, a sufficient soil cover was not obtained for mulching treatments in 2011 and only partially in 2012. In contrast to the vast majority of literature that stresses the positive and even dramatically positive effects of conservation tillage treatments compared with conventional agricultural management techniques, our results reveal possible problems when applying these best management techniques in small scale farming systems. © 2015 Elsevier B.V. Source

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