bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the method of collecting suspended sediment from large rivers by discharge‐weighted pumping and separation by continuous‐flow centrifugation
Authors: Moody John A. , Meade Robert H. 
Published: February 2007

AbstractA method for collecting suspended sediment samples has been developed that pumps a discharge‐weighted volume of water from fixed depths at four to 40 locations across a river and separates the suspended sediment in the sample using a continuous‐flow centrifuge. The efficacy of the method is evaluated by comparing the particle size distributions of sediment collected by the discharge‐weighted pumping method with the particle size distributions of sediment collected by depth integration and separated by gravitational settling. The pumping method was found to undersample the suspended sand sized particles (> 63 μm) but to collect a representative sample of the suspended silt and clay sized particles (< 63 μm). The centrifuge separated the silt and clay sized particles (< 63 μm) into three fractions. Based on the average results of processing 17 samples from the Mississippi River and several of its large tributaries in 1990, about 10% of the silt and clay sized material was trapped in a centrifuge bowl‐bottom sealing unit containing the nozzle and consisted of mostly medium and coarse silt from 16 to 63 μm. About 74% was retained on a Teflon liner in the centrifuge bowl and consisted of sizes from 0–1 to 63 μm. About 9% was discharged from the centrifuge in the effluent and was finer than 0–1 μm. About 7% was lost during the processes of removing the wet sediment fractions from the centrifuge, drying and weighing.The success of the discharge‐weighted pumping method depends on how homogeneously the silt and clay sized particles (< 63 μm) are distributed in the vertical direction in the river. The degree of homogeneity depends on the composition and degree of aggregation of the suspended sediment particles.
Mountain hydrology of Canada and China: A case study in comparative hydrology
Authors: Woo Ming‐Ko , Liu Changming 
Published: February 2007

AbstractComparative hydrology attempts to identify regions with similar environmental attributes and then compares the hydrological activities in these regions to facilitate the transfer of knowledge and exchange of techniques. As a case study, the mountainous regions of Canada and China were compared. Vertical zonation is a characteristic feature of such regions, generating contrasts in microclimate, vegetation, soil and the resultant hydrological responses. An increase in precipitation with altitude is modified by aspect and other local factors. In temperate and colder latitudes, snow and ice are important, especially at higher elevations. Both countries have conducted many hydrological studies on snow and glaciers, but evaporation in mountainous terrain merits more attention. Runoff from mountainous catchments is often generated by a range of processes including rainfall, snowmelt and glacier melt, and runoff response to water input tends to be rapid. This study identifies some of the strengths and weaknesses of our current knowledge of mountain hydrology in both countries, and suggests that a more comprehensive treatment of the subject will improve the prediction of the hydrological behaviour of such regions.
Accuracy of kinematic wave and diffusion wave approximations for space‐independent flows on infiltrating surfaces
Authors: Singh V. P. 
Published: February 2007

AbstractError equations for the kinematic wave and diffusion wave approximations were derived under simplified conditions for space‐independent flows occurring on infiltrating planes or channels. These equations specify error as a function of time in the flow hydrograph. The kinematic wave, diffusion wave and dynamic wave solutions were parameterized through a dimensionless parameter γ which is dependent on the initial conditions. This parameter reflects the effect of initial flow depth, channel bed slope, lateral inflow and channel roughness when the initial condition is non‐vanishing; it reflects the effect of bed slope, channel roughness, lateral inflow and infiltration when the initial condition is vanishing. The error equations were found to be the Riccati equation.
Effect of mining and related activities on the sediment trace element geochemistry of Lake Coeur D'Alene, Idaho, USA part II: Subsurface sediments
Authors: Horowitz Arthur J. , Elrick Kent A. , Robbins John A. , Cook Robert B. 
Published: February 2007

AbstractDuring the summer of 1990, 12 gravity cores were collected in Lake Coeur d'Alene, Idaho at various depths and in a variety of depositional environments. All core subsamples were analysed to determine the bulk sediment chemistry; selected subsamples were analysed for trace element partitioning and 137Cs activity. The purpose of these analyses was to determine the trace element concentrations and distributions in the sediment column and to try to establish a trace element geochemical history of the lake in relation to mining and mining‐related discharge operations in the area.Substantial portions of the near‐surface sediments in Lake Coeur d'Alene are markedly enriched in Ag, As, Cd, Hg, Pb, Sb and Zn, and slightly enriched in Cu, Fe and Mn. Variations in the thickness of the trace element‐rich sediments, which range from more than 119 cm to as little as 17 cm, indicate that the source of much of this material is the Coeur d'Alene River. An estimated 75 million tonnes of trace element‐rich sediments have been deposited on or in the lake bed. Estimated trace element masses in excess of those considered representative of background conditions range from a high of 468 000 tonnes of Pb to a low of 260 tonnes of Hg.The similarity between the trace element‐rich surface and subsurface sediments with respect to their location, their bulk chemistry, their interelement relations and their trace element partitioning indicate that the sources and/or concentrating mechanisms causing the trace element enrichment in the lake sediments have probably been the same through‐out their depositional history. Based on a Mt St Helens'ash layer from the 1980 eruption, ages estimated from 137Cs activity and the presence of 80 discernible and presumably annual layers in a core collected near the Coeur d'Alene River delta indicate that deposition rates for the trace element‐rich sediments have ranges from 2.1 to 1.3 cm/year. These data also indicate that the deposition of trace element‐rich sediments began, at least in the Coeur d'Alene River delta, some time between 1895 and 1910, dates consistent with the onset of mining and ore processing activities that began in the area in the 1880s.
Sensitivity to space and time resolution of a hydrological model using digital elevation data
Authors: Bruneau P. , Gascuel‐Odoux C. , Robin P. , Merot Ph. , Beven K. 
Published: February 2007

AbstractThe space and time resolutions used for the input variables of a distributed hydrological model have a sufficient impact on the model results. This resolution depends on the required accuracy, experimental site and the processes and variables taken into account in the hydrological model. The influence of space and time resolution is studied here for the case of TOPMODEL, a model based on the variable contributing area concept, applied to an experimental 12 km2 catchment (Coët‐Dan, Brittany, France) during a two month winter period. A sensitivity analysis to space and time resolution is performed first for input variables derived from the digital elevation data, secondly for the optimized values of the TOPMODEL parameters and finally for modelling efficiency. This analysis clearly shows that a relevant domain of space and time resolutions where efficiency is fairly constant can be defined for the input topographic variables, as opposed to another domain of larger resolutions that induces a strong decrease of modelling efficiency. It also shows that the use of a single set of parameters, defined as mean values of parameters on this relevant domain of resolution, does not modify the accuracy of modelling. The sensitivity of the parameters to space and time resolution allows the physical significance of the parameter values to be discussed.
Potential of turbidity monitoring for measuring the transport of suspended solids in streams
Authors: Gippel Christopher James 
Published: February 2007

AbstractInvestigating the transport of suspended solids by water sampling usually leads to an underestimation of loads and an unrealistically high sampling frequency is required to properly characterize temporal trends. An alternative method is to use in situ optical turbidimeters to estimate the suspended solids concentration; however, the relationship between turbidity and suspended solids concentration is potentially confounded by variations in particle size, particle composition and water colour. Field measurements, and laboratory measurements using the type of natural material suspended in streamwater, were made to quantify the influences of these factors on nephelometric turbidity (Hach 2100A) and attenuance turbidity (Partech 7000 3RP MKII). The attenuance turbidity was approximately 2.5 times higher than nephelometric turbidity. The turbidity instruments were most sensitive to dispersions with a median diameter of 1.2‐1.4γm. Particle size variation can cause the turbidity to vary by a factor of four for the same concentration of suspended solids. However, the numerous close correlations between turbidity and suspended solids concentration reported previously suggests that either the particle size variations are not usually great, or that particle size variations are often associated with variations in suspended solids concentration. For the same concentration and particle size, organic particles gave attenuance turbidity values two to three times higher than mineral particles. However, shortterm temporal variations from purely organic to purely mineral particle loads are rare in nature, so variations in the percentage of organic matter in the paniculate load will not confound turbidity to this extent. Coloured dissolved organic matter is unlikely to alter the turbidity reading by more than 10%. An adequate relationship between turbidity measured in the field and suspended solids concentration should be expected in most situations. Some variance can be tolerated because a continuous estimate of suspended solids concentration overcomes the problem of infrequent sampling, which is the greatest source of error in the estimation of stream sediment loads.
Soil erosion and overland flow in forested areas with pine plantations at coastal mountain range, central chile
Authors: Oyarzun C. E. , Peña L. 
Published: February 2007

AbstractThe effects of timber‐cutting on sediment concentrations, soil loss and overland flow in an insigne pine (Pinus radiata) plantation were studied in a mountain watershed of the Cordillera de la Costa, central Chile. Soil formation rates for the lithological conditions of the watershed were estimated.Soil loss measurements on the plantation were taken in 100 m2 plots, equipped with Coshocton samplers, during the years 1991 and 1992. Treatments were: clear‐cutting no residues/burned, clear‐cutting with residues and undisturbed controls.First‐year soil losses were greater from the no residues/burned (2128 kg ha−1) than from the residues (1219 kg ha−1) or undisturbed (48 kg ha−1) plots. During the second post‐treatment year, soil loss was greater from the burned plots (1349 kg ha−1) than from the residues (243 kg ha−1) or the undisturbed (72 kg ha−1) plots. Sediment concentrations for the three treatments were 561, 340 and 59 mgl‐1 during the first year, and 400, 150 and 83 mgl−1 in the second year. Runoff from the no residues/burned plots was greater than from residues or undisturbed plots during the two post‐treatment years. Long‐term soil losses were projected to average 240 kg ha−1 yr−1 from areas without residues/burned and 120 kg ha−1 yr−1 in areas with residues treatment, over a 25 year rotation period, whereas control areas were projected to average 60 kg ha−1 yr−1.
Estimation of vertical water and heat fluxes in the semi‐confined aquifers in tokyo metropolitan area, japan
Authors: Dapaah‐Siakwan S. , Kayane Isamu 
Published: February 2007

AbstractGroundwater circulation is known to be one of the agents responsible for the redistribution of geothermal energy by acting as a source or sink in the course of its movement through porous media. Heat transport in groundwater systems is considered to be a coupled process and the theory based on this was used to analyse temperature profiles of 30 thermally stable observation wells in a deep, semi‐confined aquifer system in the Tokyo Metropolitan area. Vertical water fluxes in the semi‐confined aquifers and the associated upward heat fluxes were estimated from a heat flux equation that describes convection and conduction processes of heat transport in one dimension. The vertical downward water fluxes in Shitamachi lowland, Musashino and Tachikawa terraces were 0.69.26.91 × 10−9, 1.46‐70.92 × 10−9 and 2.61.2204 × 10−9 m/s, respectively. A vertical upward water flux of 1.80‐33.60 × 10−9 m/s was estimated in Shitamachi lowland. The water flux generally decreased with increasing depth for observation wells which intercepted more than one semi‐confining layer. The estimated upward heat fluxes for Shitamachi lowland, Musashino and Tachikawa terraces were 0.32‐1.12, 0.49‐1.21 and 1.00‐11.62 W/m2, respectively. The heat flux was highest in Tachikawa terrace where a major fault, the Tachikawa fault, is located. Generally, the estimated heat flux was higher in the semi‐confining layers than in the aquifers. Areas with heat sources and sinks as well as groundwater flow patterns in the semi‐confined aquifers were revealed by heat flux and temperature distributions in the study area.
Influence of sea salt on stream water chemistry in an upland afforested catchment
Authors: Soulsby Christopher 
Published: February 2007

AbstractThe chemistry of bulk precipitation and stream water was monitored in an acidic afforested catchment at Llyn Brianne in upland Wales between 1985 and 1990. Throughfall, stemflow and soil water chemistry were also monitored between 1988 and 1989. Marine‐derived solutes dominated the ionic composition of precipitation and stream water, which had mean Cl concentrations of 113 μequiv. 1−1 and 245 μequiv. 1−1, respectively. The higher concentrations in stream water reflect occult and dry deposition on the forest canopy and the effect of interception and transpiration losses. Chloride variations in stream water (112‐454μequiv. 1−1) were damped compared with bulk precipitation (28‐762μequiv. 1−1) due to the mixing of event (‘new’) water with pre‐event (‘old’) water in the catchment soils. A storm episode monitored in the catchment in April 1989 was associated with high sea salt inputs and Cl concentrations in throughfall (1466μequiv. 1−1) and storm runoff were exceptionally high (392μequiv. 1−1). The Cl signal in stream water during the episode was consistent with an event (‘new’) water contribution to the storm response. However, a short‐term hydrochemical budget estimated that although Cl outputs from the catchment during the event (1.17 kg ha−1) were equivalent to 8% of inputs in throughfall and stemflow, the storm runoff was equivalent to 32% of effective precipitation. This indicates that pre‐event (‘old’) water was the dominant source (> 75%) of storm runoff. Although sea salt inputs during the event had a marked impact on stream water chemistry, the anomalously high levels of acidity sometimes associated with sea salt events were not observed in this particular study.
Topographic zonation of infiltration in the hilly loess region, north china
Authors: Li Gang , Luk Shiu Hung , Cai Qiang Guo 
Published: February 2007

AbstractField infiltration tests using portable rainfall infiltrometers were conducted in the Wangjiagou experimental basin in the hilly loess region of north China. Based on data collected at 27 sites, a topographic zonation of infiltration characteristics was observed. The average steady infiltration rate and the average ponding time decreased from the hilltop to the hillslope and further decreased to the gully wall. Such a zonation is closely related to the variations of topography, soil and land use conditions in the study area. A general infiltration model is proposed. Collected field data are used to establish the applicability of the proposed model in the study area.
Scale issues in hydrological modelling: A review
Authors: Blöschl G. , Sivapalan M. 
Published: February 2007

AbstractA framework is provided for scaling and scale issues in hydrology. The first section gives some basic definitions. This is important as researchers do not seem to have agreed on the meaning of concepts such as scale or upscaling. ‘Process scale’, ‘observation scale’ and ‘modelling (working) scale’ require different definitions. The second section discusses heterogeneity and variability in catchments and touches on the implications of randomness and organization for scaling. The third section addresses the linkages across scales from a modelling point of view. It is argued that upscaling typically consists of two steps: distributing and aggregating. Conversely, downscaling involves disaggregation and singling out. Different approaches are discussed for linking state variables, parameters, inputs and conceptualizations across scales. This section also deals with distributed parameter models, which are one way of linking conceptualizations across scales. The fourth section addresses the linkages across scales from a more holistic perspective dealing with dimensional analysis and similarity concepts. The main difference to the modelling point of view is that dimensional analysis and similarity concepts deal with complex processes in a much simpler fashion. Examples of dimensional analysis, similarity analysis and functional normalization in catchment hydrology are given. This section also briefly discusses fractals, which are a popular tool for quantifying variability across scales. The fifth section focuses on one particular aspect of this holistic view, discussing stream network analysis. The paper concludes with identifying key issues and gives some directions for future research.
Investigating the representative elementary area concept: An approach based on field data
Authors: Woods Ross , Sivapalan Murugesu , Duncan Maurice 
Published: February 2007

AbstractChanging the scale of observation or averaging has a significant, but poorly understood, impact on the apparent variability of hydrological quantities. The representative elementary area (REA) concept is used as a motivation for measuring inter‐storm streamflow and calculating wetness index distributions for the subcatchments of two small study areas in New Zealand. Small subcatchments are combined to provide larger scale samples, and then the variance of specific discharge between similar sized subcatchments is calculated. For small subcatchments (area less than ∼1 km2) this variance is found to decrease with area more quickly than might be expected if the catchments were random samples. Such behaviour is tentatively interpreted as evidence supporting the concept of ‘organization’. At larger scales, variance between catchments decreases in a way that is consistent with sampling from a stationary random field. The results from the streamflow data are reinforced by an analysis of topographic data for the two study areas, although some questions remain open.Both the flow and topographic data support the idea that it is possible to find an averaging scale where the variability between catchments is sufficiently small for a ‘distribution function’ approach to be used in distributed rainfall‐runoff modelling. Consistent estimates of the scale at which the study areas become stationary (0.5 km2 for Little Akaloa, 2 km2 for Lewis) are obtained using both flow and topographic data. The data support a pragmatic REA concept which allows meaningful averages to be formed: this may be a useful base for further conceptual developments, but it is not appropriate for a classical continuum approach. Further conceptual development combined with field measurement and computer simulation are still required for the REA to have operational impacts. In particular, it is not clear which models are appropriate for use at the REA scale.
Scaling behaviour of hydrological fluxes and variables: Empirical studies using a hydrological model and remote sensing data
Authors: Wood Eric F. 
Published: February 2007

AbstractThe effects of small‐scale heterogeneity in land surface characteristics on the large‐scale fluxes of water and energy in the land‐atmosphere system has become a central focus of many of the climatology research experiments. The acquisition of high resolution land surface data through remote sensing and intensive land‐climatology field experiments (such as HAPEX and FIFE) has provided data to investigate the interactions between microscale land‐atmosphere interactions and macroscale models. One essential research question is how to account for the small‐scale heterogeneities and whether ‘effective’ parameters can be used in the macroscale models. To address this question of scaling, it is important to carry out modelling studies by analysing the spatial behaviour of process‐based, distributed land‐atmospheric models and available data from land surface climate experiments such as those designed under ISLSCP (e.g. FIFE and BOREAS) and HAPEX (e.g. HAPEX‐MOBILY, HAPEX‐SAHEL) and GEWEX (e.g. GCIP) and from smaller scale remote sensing experiments. Using data from FIFE'87 and WASHITA'92, a soil moisture remote sensing experiment, analyses are presented on how the land surface hydrology during rain events and between rain event varies; specifically, runoff during rain events, evaporation between rain events and soil moisture. The analysis with FIFE'87 data suggests that the scale at which a macroscale model becomes valid, the representative elementary scale (REA), is of the order of 1.5‐3 correlation lengths, which for the land processes investigated appear to be about 750‐1250 m. For the Washita catchment data, analysis of soil‐based infiltration data supports an REA of this spatial scale, but model derived and remotely sensed soil moisture data appear to suggest a larger scale. Statistical self‐similarity is investigated to further understand how soil moisture scales over the Washita catchment and to provide a basis for macroscale models.