bluuebunny/crossref_metadata_2025 huggingface dataset:
Flame height correlation and upward flame spread modelling
Authors: Chung Tsai Kuang‐ , Drysdale Dougal
Published: January 2003

Previous work has demonstrated that flame height is one of the two most important parameters determining the rate of vertical flame spread on a wall. Flame spread models rely on empirical flame height correlations of the form Xf=KQ̇′n, but there have been no carefully controlled experiments designed to establish the validity of such correlations and there are no data for values of Q̇′< c.25 kW/m. Two new sets of data are presented here, one based on experiments with 6 mm thick PMMA slabs (heights 25–250 mm, width 50–150 mm) as the fire source, measuring Q̇′ and Xf simultaneously. This set relates to the early stages of a wall fire when Q̇′< 30 kW/m. The other set of data was obtained with a vertical gas‐fired panel which consisted of an array of 14 independent burners arranged to allow the aspect ratio of the burning surface to be varied. The data confirm that the flame height correlates with Q̇′, but reveal (inter alia) that there are two regions, for values of Q̇′ greater than and less than c. 20 kW/m.

An existing upward flame spread model was modified to allow these two correlations to be incorporated to predict the development of a small fire on a vertical surface for these two regions, which would provide more realistic modelling information. Copyright © 2002 John Wiley & Sons, Ltd.
Reducing salinity and organic contaminants in the Pearl Harbor dredged material using soil amendments and plants
Authors: Hue N. V. , Campbell S. , Li Q. X. , Lee C. R. , Fong J.
Published: January 2003

Phytoremediation is an emerging technique that can be used to economically remediate sites contaminated with
trace elements and/or man‐made organic contaminants. This technique was used on Pearl Harbor (Oahu,
Hawaii) dredged material (PHDM) containing polycyclic aromatic hydrocarbons (PAHs) and
some heavy metals. The dredged material was first amended with a high‐calcium soil (Waialua
Mollisol) and a biosolids‐based compost at different proportions to yield varying salinity levels. A
mixture that yielded an electrical conductivity (EC, a measure of salinity) of the saturated paste
extract of 15 to 20 dS/m was identified and used to evaluate the salt tolerance of five plant species. Relative
germination and one‐month‐old biomass indicated that common bermuda grass (Cynodon
dactylon), seashore paspalum (Paspalum vaginatum), beach pea
(Vigna marina), and cow pea (Vigna unguiculata) can produce
at least 40 percent of biomass of the control at an EC of approximately 18 dS/m, suggesting the four plants are
relatively salt tolerant. In contrast, Desmodium intortum either did not germinate or died within
two weeks after germination at the same salinity level. A subsequent greenhouse experiment, using mixtures of the
PHDM (0 or 25 percent dry weight), organic amendments (10 percent leucaena green manure or
biosolids‐based compost), and a Mollisol (65 or 90 percent dry weight) in 6‐liter pots
containing 4 kilograms of material yielded the following results: (1) a combination of transplanted
seashore paspalum, seeded bermuda grass, and seeded beach pea was effective in taking up sodium (Na),
thereby reducing salinity and making the medium more amenable to diversified microbes and plants, which may be
effective PAH degraders; (2) total PAH concentration was reduced by about 30 percent after three
months of active plant growth, but degradation of individual PAH members varied significantly, however;
(3) leguminous green manure, as a soil amendment, was more effective than compost for use in bio‐
and/or phyto‐remediations; and (4) soil amendments, when applicable, could supplement
living plants in reducing organic contaminants, such as PAHs. © 2003 Wiley Periodicals, Inc. Reprinted from
Remediation Volume 12, Number 4.
An implicit pseudo‐spectral multi‐domain method for the simulation of incompressible flows
Authors: Droll P. , Schäfer M. , Serre E. , Bontoux P.
Published: January 2003

A pseudo‐spectral method for the solution of incompressible flow problems based on an iterative solver involving an implicit treatment of linearized convective terms is presented. The method allows the treatment of moderately complex geometries by means of a multi‐domain approach and it is able to cope with non‐constant fluid properties and non‐orthogonal problem domains. In addition, the fully implicit scheme yields improved stability properties as opposed to semi‐implicit schemes commonly employed. Key components of the method are a Chebyshev collocation discretization, a special pressure–correction scheme, and a restarted GMRES method with a preconditioner derived from a fast direct solver. The performance of the proposed method is investigated by considering several numerical examples of different complexity, and also includes comparisons to alternative solution approaches based on finite‐volume discretizations. Copyright © 2003 John Wiley & Sons, Ltd.
Accurate multi‐level schemes for advection
Authors: Kim Cheolwan
Published: January 2003

The upwind leapfrog method for the advection equation, which is non‐dissipative and very accurate, is extended to higher‐order and multiple dimensions. The higher‐order version is developed by extending the stencil into space and time, and an analysis of the phase error is given. The schemes are then successfully applied to the classical test cases of rotating flow, and to a more realistic problem of non‐uniform advection. Copyright © 2003 John Wiley & Sons, Ltd.
A fourth‐order compact finite difference scheme for the steady stream function–vorticity formulation of the Navier–Stokes/Boussinesq equations
Authors: Tian Zhenfu , Ge Yongbin
Published: January 2003

A fourth‐order compact finite difference scheme on the nine‐point 2D stencil is formulated for solving the steady‐state Navier–Stokes/Boussinesq equations for two‐dimensional, incompressible fluid flow and heat transfer using the stream function–vorticity formulation. The main feature of the new fourth‐order compact scheme is that it allows point‐successive overrelaxation (SOR) or point‐successive underrelaxation iteration for all Rayleigh numbers Ra of physical interest and all Prandtl numbers Pr attempted. Numerical solutions are obtained for the model problem of natural convection in a square cavity with benchmark solutions and compared with some of the accurate results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd.
Application of the method of lines to unsteady compressible Euler equations
Authors: Šolín Pavel , Segeth Karel
Published: January 2003

In the sense of method of lines, numerical solution of the unsteady compressible Euler equations in 1D, 2D and 3D is split into three steps: First, space discretization is performed by the first‐order finite volume method using several approximate Riemann solvers. Second, smoothness and Lipschitz continuity of RHS of the arising system of ordinary dimensional equations (ODEs) is analysed and its solvability is discussed. Finally, the system of ODEs is integrated in time by means of implicit and explicit higher‐order adaptive schemes offered by ODE packages ODEPACK and DDASPK, by a backward Euler scheme based on the linearization of the RHS and by higher‐order explicit Runge–Kutta methods. Time integrators are compared from several points of view, their applicability to various types of problems is discussed, and 1D, 2D and 3D numerical examples are presented. Copyright © 2003 John Wiley & Sons, Ltd.
Artificial boundary method for the exterior Stokes flow in three dimensions
Authors: Zheng Chunxiong , Han Houde
Published: January 2003

In this paper, the artificial boundary method is considered for the numerical simulation of the exterior Stokes flow in three dimensions. First, an exact relation between the normal stress and the velocity field is obtained on a spherical artificial boundary. With the relation specified on the artificial boundary, the original problem is reduced to a new one only defined on a finite domain. After that, an variational problem equivalent to the reduced problem is derived. By truncating the series term in the formulation, a sequence of approximate variational problems are obtained, which can then be solved with a suitable finite‐element scheme. Finally, a numerical example is presented to show the performance of the method. Copyright © 2003 John Wiley & Sons, Ltd.
Interfacial transfer in Tryggvason's method
Authors: Ferziger Joel H.
Published: January 2003

Tryggvason'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

The 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

Soil 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

Nitrogen 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

A 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

A 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

Runoff 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

In 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

The 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

Improved 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

Preliminary 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

Soil 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

There 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.
A decision scheme to indicate dominant hydrological flow processes on temperate grassland
Authors: Scherrer Simon , Naef Felix
Published: January 2003

A decision scheme has been developed to indicate the likely dominant runoff forming on temperate grassland hill slopes. The decision scheme was developed from data collected from sprinkler experiments on 60 m2 plots at a number of grassland sites in Switzerland. The scheme requires input of hydrological properties of the surface and each major horizon of the soil. Worked examples of the application of the decision scheme to determine the dominant hydrological processes and runoff types are given for three actual grassland hill slopes. Copyright © 2003 John Wiley & Sons, Ltd.
Towards integrating tracer studies in conceptual rainfall‐runoff models: recent insights from a sub‐arctic catchment in the Cairngorm Mountains, Scotland
Authors: Soulsby Chris , Dunn Sarah M.
Published: January 2003

Hydrochemical tracers (alkalinity and silica) were used in an end‐member mixing analysis (EMMA) of runoff sources in the 10 km2 Allt a' Mharcaidh catchment. A three‐component mixing model was used to separate the hydrograph and estimate, to a first approximation, the range of likely contributions of overland flow, shallow subsurface storm flow, and groundwater to the annual hydrograph. A conceptual, catchment‐scale rainfall‐runoff model (DIY) was also used to separate the annual hydrograph in an equivalent set of flow paths. The two approaches produced independent representations of catchment hydrology that exhibited reasonable agreement. This showed the dominance of overland flow in generating storm runoff and the important role of groundwater inputs throughout the hydrological year. Moreover, DIY was successfully adapted to simulate stream chemistry (alkalinity) at daily time steps. Sensitivity analysis showed that whilst a distinct groundwater source at the catchment scale could be identified, there was considerable uncertainty in differentiating between overland flow and subsurface storm flow in both the EMMA and DIY applications. Nevertheless, the study indicated that the complementary use of tracer analysis in EMMA can increase the confidence in conceptual model structure. However, conclusions are restricted to the specific spatial and temporal scales examined. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of flowpath dynamics in a steep unchannelled hollow in the Tanakami Mountains of Japan
Authors: Uchida Taro , Asano Yuko , Ohte Nobuhito , Mizuyama Takahisa
Published: January 2003

Simultaneous measurements of runoff, soil pore water pressure, soil temperature, and water chemistry were taken to evaluate the spatial and temporal nature of flowpaths in a steep 0·1 ha unchannelled hollow in the Tanakami Mountains of central Japan. Tensiometers showed that a saturated area formed and a downward hydraulic gradient existed continuously in the area near a spring. The amplitude of the soil–bedrock interface temperature difference near the spring was smaller than that in the upper hollow, although soil depth near the spring was smaller than in the upper hollow. This suggests that, in the small perennially saturated area near the spring, water percolates through the vadose zone mixed with water emerging from the bedrock. During summer rainstorms, the soil–bedrock interface temperature increased as the ground became saturated. Silica and sodium concentrations in the transient saturated groundwater during these episodes were significantly lower than those in the perennial groundwater, suggesting that both rainwater and shallow soil water had important effects on the formation of transient saturated groundwater on the upper slope. In this case, the streamflow varied with the soil pore water pressure on the upper slope; the soil pore water pressure in the area near the spring remained nearly constant. Moreover, the spring water temperature was almost the same as the transient groundwater temperature on the upper slope. This indicates that the transient groundwater in the upper slope flowed to the spring via lateral preferential paths. The relative inflow of bedrock groundwater to the spring decreased as rainfall increased. Copyright © 2003 John Wiley & Sons, Ltd.
Quantifying uncertainties in tracer‐based hydrograph separations: a case study for two‐, three‐ and five‐component hydrograph separations in a mountainous catchment
Authors: Uhlenbrook Stefan , Hoeg Simon
Published: January 2003

The hydrograph separation technique using natural tracers, in which different runoff components are quantified according to their chemical signature, is a widely used method for investigating runoff generation processes at the catchment scale. The first objective of this study is to demonstrate a modified methodology for separating three and five runoff components using 18O and dissolved silica as tracers. The second is to evaluate, with an uncertainty propagation technique using Gaussian error estimators, the hydrograph separation uncertainties that arise due to different error effects.

During four summer storm events, an interaction among three main runoff components having distinct dissolved silica concentrations was demonstrated for the mountainous Zastler catchment (18·4 km2, southern Black Forest Mountains, southwest Germany). The three main runoff components are surface storage (low silica, saturated and impermeable areas), shallow ground water (medium silica, periglacial and glacial drift cover), and deep ground water (high silica, crystalline detritus and hard rock aquifer). Together with the event and pre‐event water fractions of surface runoff and shallow ground water runoff, five runoff components are considered in all. Pre‐event water from shallow ground water storage dominated the total discharge during floods and was also important during low flows. Event water from shallow ground water was detectable only during the falling limb of a larger flood with high antecedent moisture conditions and during the peaks of three events with low antecedent moisture conditions. Runoff from surface storage is only significant during floods and can be composed of event and pre‐event water. The latter reacts later and is important only during the peak of the large event with high antecedent moisture conditions. Runoff from the deeper ground water behaves quite consistently (pure pre‐event water).

It is demonstrated that large relative uncertainties must be considered for the quantification of runoff components. Uncertainties are caused by: (i) tracer analysis and discharge measurement; (ii) intra‐storm variability of 18O; (iii) elevation effect of 18O and silica; (iv) solution of minerals during runoff formation; and (v) general spatial heterogeneity of tracer concentrations. The last source of error was the most significant. The error structure was analysed in detail and showed varying error significance within an event and for different events. It is shown that, for the meso‐scale catchment investigated, only qualitative results of the contribution of a runoff component can be obtained by the hydrograph separation technique. The importance of reducing errors that have the largest impact is clearly demonstrated; therefore, a targeted sampling strategy is required. Copyright © 2003 John Wiley & Sons, Ltd.
Towards reduced uncertainty in conceptual rainfall‐runoff modelling: dynamic identifiability analysis
Authors: Wagener T. , McIntyre N. , Lees M. J. , Wheater H. S. , Gupta H. V.
Published: January 2003

Conceptual modelling requires the identification of a suitable model structure and the estimation of parameter values through calibration against observed data. A lack of objective approaches to evaluate model structures and the inability of calibration procedures to distinguish between the suitability of different parameter sets are major sources of uncertainty in current modelling procedures. This paper presents an approach analysing the performance of the model in a dynamic fashion resulting in an improved use of available information. Model structures can be evaluated with respect to the failure of individual components, and periods of high information content for specific parameters can be identified. The procedure is termed dynamic identifiability analysis (DYNIA) and is applied to a model structure built from typical conceptual components. Copyright © 2003 John Wiley & Sons, Ltd.
An experimental tracer study of the role of macropores in infiltration in grassland soils
Authors: Weiler Markus , Naef Felix
Published: January 2003

Water flow in macropores is an important mechanism of infiltration in natural soils and, as such, is crucial for the prediction of runoff generation. The major flow processes controlling macropore flow are the initiation of macropore flow (water supply into macropores) and the water transfer from the macropores into the surrounding soil matrix (interaction). The water movement during infiltration and the resulting flow paths were studied with combined sprinkling and dye tracer experiments under different rainfall intensities and initial soil moisture conditions. The dye tracer was continuously applied with the sprinkling water on 1 m2 plots. After the sprinkling, horizontal and vertical soil sections were prepared for surveying dye patterns, which showed the cumulated flow pathways in the soils. These experiments were carried out on four hillslope sites covered with grassland, where earthworms mainly built the macropore system. The evaluation of the flow processes in the soil was based on classified dye patterns and measurements of water content and matric potential. The results illustrate how flow in earthworm channels influences general hydrological flow processes during extreme rainfall events. Macropore flow was initiated from the soil surface or from a saturated or partially saturated soil layer. Transfer of water from the macropores into the soil matrix was mainly influenced by the soil properties and soil water content. The permeability of the underlying bedrock in combination with this transfer of water controlled the drainage of the macropores. Finally, major effects of macropore flow processes on the hydrological response were extracted. Infiltration excess overland flow was reduced if water bypassed the less permeable layer through macropores, saturation excess overland flow was less affected by macropores, and subsurface flow was activated very rapidly because the infiltrated water bypassed the soil matrix. This study highlights the most important processes that have to be considered in order to understand better and to model infiltration in natural soils in the future. Copyright © 2003 John Wiley & Sons, Ltd.
The clinical use of films in psychotherapy
Authors: Wedding Danny , Niemiec Ryan M.
Published: January 2003

This article discusses the ways in which client attitudes about mental illness, psychotherapy, and therapists are shaped by contemporary films. Five common myths about mental illness that are promulgated by films are discussed, and the potential applications of films in psychotherapy are reviewed. Numerous examples of films relevant to psychotherapy are presented, and a clinical vignette is used to demonstrate how films can enrich and expand psychotherapy. © 2003 Wiley Periodicals, Inc. J Clin Psychol/In Session 59: 207–215, 2003.
Brefeldin A‐induced neurotoxicity in cultured spinal cord neurons
Authors: Kikuchi Seiji , Shinpo Kazuyoshi , Tsuji Sachiko , Yabe Ichiro , Niino Masaaki , Tashiro Kunio
Published: January 2003

Brefeldin A (BFA) is a fungus metabolite that is known to cause the disassembly of the Golgi complex and apoptosis in exposed cells, both of which have been suggested as playing roles in the pathogenesis of neurodegenerative diseases, particularly amyotrophic lateral sclerosis (ALS). This study showed that BFA caused neurotoxicity and apoptotic nuclear changes in cultured spinal neurons of rat spinal cord in a dose‐ and time‐dependent manner. The spinal motor neurons were more vulnerable to this neurotoxicity. The cultured spinal neurons showed irreversible disassembly of the Golgi apparatus as early as 1 hr after exposure to BFA. BFA induced the expression and activation of caspase‐12 beginning 8 hr after exposure. The level of the cleaved form of caspase‐3 had increased 12 hr after the addition of BFA. Free radical generation and loss of mitochondrial membrane potential were observed in the later stages of neurotoxicity caused by BFA. Collectively, our data suggests that BFA is an excellent agent for reproducing the pathophysiological features of ALS. This in vitro model may be useful in attempts to study the mechanisms of this neurodegenerative disease and to examine therapeutic potentials. © 2002 Wiley‐Liss, Inc.
Phosphodiesterase inhibitors are neuroprotective to cultured spinal motor neurons
Authors: Nakamizo Tomoki , Kawamata Jun , Yoshida Kohei , Kawai Yuko , Kanki Rie , Sawada Hideyuki , Kihara Takeshi , Yamashita Hirofumi , Shibasaki Hiroshi , Akaike Akinori , Shimohama Shun
Published: January 2003

We have previously reported that cyclic guanosine‐3′,5′‐monophosphate (cGMP) protects spinal motor neurons against acute reactive oxygen species (ROS)‐induced toxicity but not against chronic ROS‐induced or glutamate (Glu)‐induced toxicity. In this study, we investigated the effects of phosphodiesterase (PDE) inhibitors on the survival of cultured spinal motor neurons. Selective PDE5 inhibitors (dipyridamole, T‐1032, and zaprinast) as well as a nonselective PDE inhibitor (aminophylline) protected motor and nonmotor neurons against both acute ROS‐induced and chronic Glu‐induced neurotoxicity, whereas selective inhibitors of PDE1–4 offered no protection. 8‐Bromo‐cGMP (8br‐cGMP), a cGMP analogue, protected both motor and nonmotor neurons against acute ROS‐induced toxicity but protected only nonmotor neurons against chronic Glu‐induced toxicity. This neuroprotection was blocked by KT5823, a cGMP‐dependent protein kinase (PKG) inhibitor. Immunohistochemical staining confirmed that PDE5 and PKG are located in almost all rat lumbar spinal neurons. Furthermore, semiquantitative analysis of the immunostaining intensity revealed that PDE5 was more abundant in motor neurons than in nonmotor neurons. Our results suggest that this difference in the amount of PDE5 may be responsible for the vulnerability of motor neurons to chronic excitotoxicity. In addition, the results of this study raise the possibility that PDE5 inhibitors might be used as a treatment for amyotrophic lateral sclerosis. © 2002 Wiley‐Liss, Inc.
Vitamin D3 inhibits proinflammatory cytokines and nitric oxide production by the EOC13 microglial cell line
Authors: Lefebvre d'Hellencourt Christian , Montero‐Menei Claudia N. , Bernard Rozenn , Couez Dominique
Published: January 2003

In recent years, a neuroimmunomodulatory role for 1,25‐dihydroxyvitamine D3 [1,25(OH)2D3] has emerged. Microglial cells present a potential target for the effects of this hormone in the brain. This study focuses on the effect of 1,25(OH)2D3 on the expression and production of inflammatory cytokines and nitric oxide (NO) by the EOC13 microglial cell line. The presence of the vitamin D3 receptor in microglia was demonstrated by RT‐PCR. 1,25(OH)2D3 inhibited the production of tumor necrosis factor‐α, interleukin‐6, and NO by stimulated microglia in a concentration‐related fashion. The production of transforming growth factor‐β1 (TGF‐β1), an anti‐inflammatory cytokine, was not modified in the presence of 1,25(OH)2D3, indicating that the effects of 1,25(OH)2D3 may not involve TGF‐β1 regulation. These results show that 1,25(OH)2D3 has direct anti‐inflammatory properties on microglia. It further supports the hypothesis that 1,25(OH)2D3 could be involved in the maintenance of the brain homeostasis and may have a therapeutic potential in inflammatory pathologies of the central nervous system. © 2002 Wiley‐Liss, Inc.