bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacial transfer in Tryggvason's method
Authors: Ferziger Joel H. 
Published: January 2003

AbstractTryggvason's method computes two phase flows by smoothing the regions near the boundaries between the two fluids. This requires averaging of the fluid properties, which may differ by orders of magnitude and can lead to large errors. Traditional linear averaging produces a first order error that can be extremely large. In this paper, we show that for a number of simple test cases, averaging of the inverses of the properties can lead to a significant improvement in the quality of the results. Copyright © 2003 John Wiley & Sons, Ltd.
Application of the distributed hydrology soil vegetation model to Redfish Creek, British Columbia: model evaluation using internal catchment data
Authors: Whitaker Andrew , Alila Younes , Beckers Jos , Toews Dave 
Published: January 2003

AbstractThe Distributed Hydrology Soil Vegetation Model is applied to the Redfish Creek catchment to investigate the suitability of this model for simulation of forested mountainous watersheds in interior British Columbia and other high‐latitude and high‐altitude areas. On‐site meteorological data and GIS information on terrain parameters, forest cover, and soil cover are used to specify model input. A stepwise approach is taken in calibrating the model, in which snow accumulation and melt parameters for clear‐cut and forested areas were optimized independent of runoff production parameters. The calibrated model performs well in reproducing year‐to‐year variability in the outflow hydrograph, including peak flows. In the subsequent model performance evaluation for simulation of catchment processes, emphasis is put on elevation and temporal differences in snow accumulation and melt, spatial patterns of snowline retreat, water table depth, and internal runoff generation, using internal catchment data as much as possible. Although the overall model performance based on these criteria is found to be good, some issues regarding the simulation of internal catchment processes remain. These issues are related to the distribution of meteorological variables over the catchment and a lack of information on spatial variability in soil properties and soil saturation patterns. Present data limitations for testing internal model accuracy serve to guide future data collection at Redfish Creek. This study also illustrates the challenges that need to be overcome before distributed physically based hydrologic models can be used for simulating catchments with fewer data resources. Copyright © 2003 John Wiley & Sons, Ltd.
Soil moisture variability and land use in a seasonally arid environment
Authors: Williams A. G. , Ternan J. L. , Fitzjohn C. , de Alba S. , Perez‐Gonzalez A. 
Published: January 2003

AbstractSoil moisture patterns were recorded for six different land uses, including oak forest, matorral scrub, olives, and a cultivated field, in central Spain during 1998–99. Volumetric water content was determined using time domain reflectometry at more than 140 sites in each, extending across a range of topographic units. Soil moisture content was a function of land use, with the oak forest being wetter than either the matorral shrubby area or the cultivated site. The spatial patterns for a wet period were kriged and are presented as interpolated contour plots. Geo‐statistical analysis confirmed that the patterns were highly heterogeneous, as the variograms showed a pure nugget for each land use, except for the two olive sites, where some spatial structure could be observed. During the investigation the soils were in the dry state and the soil moisture distribution was controlled by ‘local’ factors; it was not possible to determine which environmental factor had the most influence. Copyright © 2003 John Wiley & Sons, Ltd.
Episodic increases in nitrate concentrations in streamwater due to the partial dieback of a pine forest in Japan: runoff generation processes control seasonality
Authors: Ohte Nobuhito , Tokuchi Naoko , Katsuyama Masanori , Hobara Satoru , Asano Yuko , Koba Keisuke 
Published: January 2003

AbstractNitrogen dynamics were investigated in tandem with groundwater monitoring in a temperate forest catchment in Japan, to determine the effect of the partial dieback of dominant tree stands on nutrient cycling and streamwater chemistry, especially temporal and spatial changes in the NO3− concentrations in soil and ground water. Decreased nitrogen uptake by roots and increased nitrogen supply from the litter fall that occurred with the 1992–94 pine dieback caused by pine‐wilt disease brought on a threefold increase in nitrate concentrations in streamwater and subsurface groundwater. It was found that, from 1992 to 1996, seasonal peaks occurred in the stream NO3− concentrations during the rainy season (July to August). This seasonal variation corresponded directly to groundwater levels in the riparian zone near the catchment outlet, suggesting that seasonal changes in groundwater levels were the dominant factor controlling temporal variation in stream NO3− concentrations. The mechanism of the seasonal pattern found in this watershed emphasizes the importance of hydrological seasonality with the high precipitation, groundwater levels, and runoff rates that are seen in summer in Japan, whereas in forested watersheds in Europe and the eastern USA the smaller inorganic nitrogen pools and low transportation forces simultaneously affect NO3− leaching during summer. Copyright © 2003 John Wiley & Sons, Ltd.
Runoff generation in relation to soil moisture patterns in a small Dartmoor catchment, Southwest England
Authors: Meyles Erik , Williams Andrew , Ternan Les , Dowd John 
Published: January 2003

AbstractA hydrological experiment was conducted in a small headwater catchment in southeast Dartmoor, UK, to monitor the temporal and spatial variations in soil moisture content at the hillslope scale in order to determine how the spatial organization affected runoff generation. Two distinctly different types of rainfall response were found. During the dry state the soil moisture pattern was very patchy and the increase in stream discharge was relatively small for most rainstorms. The catchment response was limited to about 10% of the area, a figure that is similar in extent to the saturated area identified in the valley bottom. During the wet state, however, modest to large storms resulted in significantly higher discharge rates. The area generating the runoff increased up to 65% of the area. The division between the two ‘preferred’ states occurred at a catchment wetness of about 0·60 cm3 cm−3. This figure was based firstly on the exceptional increase in range, as determined by geostatistical analyses, for the soil moisture content measured associated with very high stream discharges. Secondly, it was consistent with a steep rise in gradient noted for the soil moisture characteristic curves at about 0·60 cm3 cm−3. The greater catchment responses were therefore dependent on the pore size distribution plus other soil characteristics and the connectivity between the wet areas. Copyright © 2003 John Wiley & Sons, Ltd.
Checking a process‐based catchment model by artificial neural networks
Authors: Lischeid Gunnar , Uhlenbrook Stefan 
Published: January 2003

AbstractA process‐based, conceptual runoff model, the tracer‐aided catchment (TAC) model, is developed and applied to the 40 km2 Brugga catchment in the Black Forest Mountains of southwest Germany. The model accounts for different runoff generation processes and runoff components. A lumped artificial neural network (ANN) model was also applied using the same data set. We compared the output from the two models in an effort to improve the efficiency of the TAC model and its model structure using physical and chemical data. Both approaches yielded comparably good results for daily discharge simulation. The TAC model, which uses spatially distributed input data, was superior to the lumped ANN model in only one case. Dissolved silica concentration in catchment runoff was used to assess the runoff components mixing approach of the conceptual TAC model. The ANN simulation of silica time series was superior to that of the TAC model. However, using modelled discharge values instead of measured data markedly weakened the silica predictions and resulted in a performance similar to the TAC model. We conclude that this reflects the inevitable non‐linear error propagation within the TAC model. The ANN silica model improved substantially when hourly data were used instead of daily data. According to the ANN, silica dynamics are characterized by hysteresis loops in the discharge–silica concentration relationship in the short term. In addition, this relationship depends on the antecedent moisture conditions in the medium term. About 87% of the hourly silica time series variance was explained by non‐linear regression with the hydrograph only. The implications of these findings are as follows. A simulation of the silica dynamics is possible using rather simple models that take into account the dynamics described above. In this respect, the TAC approach was confirmed by the ANN. However, an appropriate silica modelling time step must be shorter than daily values to be in line with the process time scale. Last but not least, the silica time series were assumed to reflect the spatial distribution of single hydrotopes to the catchment runoff during single storms, and thus to provide an independent check for the spatially distributed model in addition to the hydrograph. This has proven wrong, as the information provided by the silica data is highly redundant to that of the hydrograph, illustrated by the fact that the silica dynamics can be well described by the empirical model without requiring any spatial information. Copyright © 2003 John Wiley & Sons, Ltd.
Runoff generation from successive simulated rainfalls on a rocky, semi‐arid, Mediterranean hillslope
Authors: Lange J. , Greenbaum N. , Husary S. , Ghanem M. , Leibundgut C. , Schick A. P. 
Published: January 2003

AbstractRunoff generation in a Mediterranean carbonate rock environment—the Judaean Mountains, West Bank and Israel—was studied by a 2 day sprinkling experiment on an 18 × 10 m2 plot. During the first day, three spells of 24·1 mm h−1 (12·3 mm), 27·8 mm h−1 (12·3 mm) and 14·4 mm h−1 (12·5 mm) were applied, almost saturating the runoff plot. On the second day, 20 h later, two spells of 18·7 mm h−1 (34·3 mm) and 35·2 mm h−1 (25·4 mm) followed. Surface runoff was a combination of infiltration excess runoff from rocky portions of the plot and saturation excess runoff from areas covered by soil. Soil saturation was accelerated by lateral runoff from adjacent rocky areas. Once the plot was saturated, 80–90% of the applied rainfall became surface runoff. Significantly different concentrations of chloride, sulphate, and nitrate ions in the sprinkled water on two successive days served as tracers. During the second day a two‐component hydrograph separation pointed to the importance of shallow reservoirs playing active parts in runoff generation. About 14% of the flow collected during the second day originated from water applied during the first day. During the second day of sprinkling, both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow. It is hypothesized that, at least during high‐magnitude rainfall, the steep rocky slopes investigated might be regarded as flood‐generating zones rather than areas of pronounced recharge into the underlying Yarkon–Taninim aquifer. Copyright © 2003 John Wiley & Sons, Ltd.
A comparative study in modelling runoff and its components in two mountainous catchments
Authors: Gurtz Joachim , Zappa Massimiliano , Jasper Karsten , Lang Herbert , Verbunt Mark , Badoux Alexandre , Vitvar Tomas 
Published: January 2003

AbstractIn mountainous catchments the quality of runoff modelling depends strongly on the assessment of the spatial differences in the generation of the various runoff components and of the flow paths as coupled with the amount and intensity of precipitation and/or the snow melting. These catchments are also suitable for the intercomparison of different kinds of hydrological models, particularly of different approaches for the simulation of runoff generation. Two differently structured catchment models were applied on the pre‐alpine Rietholzbach research catchment (3·2 km2) within the period 1981–98 and on the high‐alpine Dischmabach catchment (43 km2) within the period 1981–96 for the simulation of hydrological processes and of the runoff hydrographs. The models adopted are the more physically based WaSiM‐ETH model, with grid‐oriented computation of the water balance elements, and the rather conceptual PREVAH model, based on hydrological response units. The simulation results and the differences resulting from the application of the two models are discussed and compared with the observed catchment discharges, with measurements of evapotranspiration, soil moisture, outflow of a lysimeter, and of groundwater levels in three access tubes. The model intercomparison indicates that the two approaches for determining runoff generation with different degrees of complexity performed with similar statistical efficiency over a period longer than 15 years. The analysis of the simulated runoff components shows that the interflow is the main runoff component and that the portion of the runoff components depends strongly on the approach used. The snowmelt model component is of decisive importance in the snowmelt season and needs to take into account the role of air temperature and radiation for simulating runoff generation in a spatially distributed manner. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling runoff generation in a forested catchment in southern Finland
Authors: Koivusalo Harri , Kokkonen Teemu 
Published: January 2003

AbstractThe main objective of this study is to identify runoff generation mechanisms in a forested catchment (0·18 km2) by comparing model simulations against measurements of groundwater levels and streamflow, and against separation of runoff components based on isotope tracer analysis. The hydrological model used in this study had a physical basis, and it consisted of separate procedures for canopy, snow, and hillslope processes, and for routing in the channel network. This paper concentrates on calibration and validation of the hillslope and routing procedures. Winter and summer seasons were examined separately in order to isolate different mechanisms controlling groundwater level behaviour. The results indicated that seasonal runoff dynamics could be replicated without calibration of the hillslope procedure against measured streamflow. The routing procedure could merely delay the runoff input it received from the hillslope procedure, and it had no influence on how large a share of a throughfall/snowmelt event, under different preceding climatic conditions, eventually emerged as streamflow. Comparison against isotope tracer data suggested that use of groundwater level measurements in the model calibration could lead to a more plausible simulation of new and old water contributions to streamflow. Still, the modelled new water fraction in streamflow was nearly twice as large as the fraction derived from isotope tracer analysis. Improvement of the model structure towards a more realistic separation of runoff components would require the model to consider residence times of water in different parts of the soil domain. Copyright © 2003 John Wiley & Sons, Ltd.
Parameter identification for conceptual modelling using combined behavioural knowledge
Authors: Dunn Sarah M. , Soulsby Chris , Lilly Allan 
Published: January 2003

AbstractImproved methods for identification of conceptual parameter values are necessary if hydrological models are to be applied to catchments other than those to which they have been specifically calibrated. A technique has been devised to calculate conceptual parameter sets of a semi‐distributed hydrological model using a soil hydrological classification in addition to topographic data. The method is tested in this paper by converting multiple parameter sets, calibrated to two separate catchments, into parameter sets for a third catchment.The prediction capabilities of the parameter sets are studied for the new catchment in terms of both simulation of total streamflow and the separation of that flow into three components, corresponding to groundwater recharge, sub‐surface flow, and surface runoff. The results from an end‐member mixing analysis (EMMA) using geochemical tracers are employed to assess the flow separation. Results from the simulations demonstrate that there is quite wide variability in the success of the parameter sets at predicting streamflow for the new catchment. There is also considerable variation in the predicted stream flow separation, with only 28 out of 500 simulations giving a comparable result to the EMMA. By accepting or rejecting simulations using these results, the EMMA can be used to reduce the structural uncertainty of the model. However, it does not help to reduce constraints on acceptable parameter values for the simulations, and further research is still necessary to improve parameter identifiability. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling hydrologic responses in a small forested catchment (Panola Mountain, Georgia, USA): a comparison of the original and a new dynamic TOPMODEL
Authors: Peters Norman E. , Freer James , Beven Keith 
Published: January 2003

AbstractPreliminary modelling results for a new version of the rainfall‐runoff model TOPMODEL, dynamic TOPMODEL, are compared with those of the original TOPMODEL formulation for predicting streamflow at the Panola Mountain Research Watershed, Georgia. Dynamic TOPMODEL uses a kinematic wave routing of subsurface flow, which allows for dynamically variable upslope contributing areas, while retaining the concept of hydrological similarity to increase computational efficiency. Model performance in predicting discharge was assessed for the original TOPMODEL and for one landscape unit (LU) and three LU versions of the dynamic TOPMODEL (a bare rock area, hillslope with regolith <1 m, and a riparian zone with regolith ⩽5 m). All simulations used a 30 min time step for each of three water years. Each 1‐LU model underpredicted the peak streamflow, and generally overpredicted recession streamflow during wet periods and underpredicted during dry periods. The difference between predicted recession streamflow generally was less for the dynamic TOPMODEL and smallest for the 3‐LU model. Bayesian combination of results for different water years within the GLUE methodology left no behavioural original or 1‐LU dynamic models and only 168 (of 96 000 sample parameter sets) for the 3‐LU model. The efficiency for the streamflow prediction of the best 3‐LU model was 0·83 for an individual year, but the results suggest that further improvements could be made. Copyright © 2003 John Wiley & Sons, Ltd.
Soil water repellency as a potential parameter in rainfall‐runoff modelling: experimental evidence at point to catchment scales from Portugal
Authors: Doerr S. H. , Ferreira A. J. D. , Walsh R. P. D. , Shakesby R. A. , Leighton‐Boyce G. , Coelho C. O. A. 
Published: January 2003

AbstractSoil water repellency is generally thought to enhance runoff responses, thus representing a potentially important factor in hydrological modelling. Attempts to quantify its impacts have, however, either focused on soil profiles or plot scales and/or have been unable unequivocally to isolate repellency effects from other hydrologically important parameters. This research gap is addressed here by comparing responses of the same soil or terrain at a range of scales in highly repellent and wettable states, thereby limiting the impact of other variables. Hydrological responses of forest soils in north‐central Portugal are assessed using laboratory wetting and rainfall simulation experiments at the point (0·002 m2) and microplot scales (0·12 m2), and field runoff responses from plot (16 m2) and catchment scales (0·33 km2).At the point scale, water repellency reduced soil wetting by a factor of >700 and increased mean runoff for a microplot from 1·5 to 53% during the first 9 min of a simulated rainstorm. At the field‐plot scale impacts are evident, but less dramatic, with 16 of 45 of storms following dry, repellent conditions producing >3% overland flow compared with only one of 60 storms following moist, wettable conditions. In contrast, at the catchment scale, storm runoff responses were lower following dry, repellent, conditions than with moist, wettable conditions, although the time‐to‐peak was on average 62% shorter for the former compared with the latter conditions. The reduced correspondence between the scales is attributed mainly to increased capture of locally generated overland flow at the catchment scale by bypass routeways that are under‐represented at point and plot scales.It is concluded that addressing water repellency in distributed hydrological modelling has considerable potential for improving predictions for affected regions, but that impacts may vary considerably from those found in the Portuguese case example. Key parameters for determining its impacts are its severity, spatial distribution, transient characteristics, and the character and spatial distribution of any bypass routeways and wettable subsoil. Copyright © 2003 John Wiley & Sons, Ltd.
Simulating interactions between saturated and unsaturated storage in a conceptual runoff model
Authors: Seibert Jan , Rodhe Allan , Bishop Kevin 
Published: January 2003

AbstractThere is an increasing demand for modelling the fluxes of chemical constituents at the catchment scale. Conceptual runoff models provide a basis for such modelling tasks provided that they capture the essential hydrological processes. However, most conceptual models do not fully address interactions between unsaturated and saturated storage. This can lead to unrealistic simulations for watersheds with shallow groundwater, where a large part of the soil volume can contribute to both the unsaturated and the saturated storage, depending on groundwater levels. Adding a small amount of water to the saturated storage will cause a significant amount of water stored in the unsaturated zone to change its status to ‘saturated’. The maximum volume of the unsaturated storage also decreases with rising groundwater levels, i.e. increasing saturated storage. In this study, a new model concept was proposed in which special emphasis was put on the interaction between saturated and unsaturated storage. The total storage was divided into two compartments, representing saturated and unsaturated storage, with a boundary moving up and down in response to the water budget of the compartments. Groundwater dynamics show a distinct pattern along the hillslope studied. Groundwater levels in an area close to the stream had dynamics similar to runoff, whereas levels further upslope responded to rainfall with a delay. To represent these differences in the model, the hillslope was subdivided into a riparian and an upslope reservoir. The performance of the new model was compared with that of simpler model variants without spatial differentiation and with or without the new formulation allowing for interactions between unsaturated and saturated storage. The new model approach provided the best results for simulating both runoff and groundwater dynamics. The subdivision of the hillslope accounted for most of the performance increase. To test the model structure further, 18O concentrations in the stream were simulated and compared with measured values. Copyright © 2003 John Wiley & Sons, Ltd.