bluuebunny/crossref_metadata_2025_split huggingface dataset:
Factors controlling the major ion chemistry of streams in the blue ridge and valley and ridge physiographic provinces of Virginia and Maryland
Authors: Puckett Larry J. , Bricker Owen P. 
Published: February 2007

AbstractThe factors controlling the chemistry of 69 low‐order streams in the Blue Ridge and Valley and Ridge physiographic provinces of Virginia and Maryland were studied over a 13‐month period. Principal component analysis was used to examine regional patterns in stream chemistry and to examine the degree to which the chemistry of low‐order streams is controlled by the bedrock upon which they flow. Streams clustered into regionally isolated groups, strongly related to bedrock type, with SO2−4 and HCO−3 the chemical variables of most importance. Sulphate concentrations appear to be strongly controlled by climate and hydrology, and sorption in the soils within the watershed. Much of the atmospherically derived SO2−4 accumulates in watersheds during the growing season and is later flushed out. Weathering reactions were found to be particularly important in the production of HCO−3, accounting for 91 per cent on an annual basis, and export of divalent cations from these watersheds, accounting for 48–50 per cent on an annual basis. About half of non‐anthropogenic Na+ was derived from weathering of silicates, whereas nearly all K+ was identified with leaching by SO2−4. Water chemistry was strongly related to the rock type in the watershed and the weatherability of the component minerals. Rock type is not a randomly distributed function; instead, it is controlled by geologic factors that result in clusters of similar rock types in a given region. When planning large synoptic studies, it is extremely important to consider that a sampling scheme based on random sampling of a non‐randomly distributed function May, not provide the most accurate representation of the variables of interest. Instead, a hierarchical sampling scheme May, be indicated. Our results also suggest that, although one sample in time May, be sufficient to characterize the primary geochemical factors controlling stream chemistry throughout the year, it May, not be sufficient to detect subtle, flow‐related alterations in chemistry.
Estimating the effects of spatial variability of infiltration on the output of a distributed runoff and soil erosion model using Monte Carlo methods
Authors: De Roo A. P. J. , Hazelhoff L. , Heuvelink G. B. M. 
Published: February 2007

AbstractMonte Carlo procedures were used to evaluate the effects of spatial variations in the values of the infiltration parameter on the results of the ANSWERS distributed runoff and erosion model. Simulation results obtained were compared with measured values. Field infiltration measurements indicated spatial correlation at much smaller distances than the size of an element. Therefore, at first only the error of the mean had to be taken into consideration for block infiltration rates. Consequently, not only single hydrographs were produced, but also error bands. Secondly, nine other hypothetical spatial correlation structures were also evaluated using Monte Carlo methods. in particular at low nugget variances, increasing spatial correlation of infiltration resulted in increasing coefficients of variation in model outputs.In general, rainstorms with low rainfall intensities were more difficult to simulate accurately than extreme events with high rainfall intensities. This is explained by the greater influence of the infiltration uncertainties at low rainfall intensities.
Developing a sediment budget for a small drainage basin in Australia
Authors: Loughran R. J. , Campbell B. L. , Shelly D. J. , Elliott G. L. 
Published: February 2007

AbstractA sediment budget was developed for the 1.7 km2 Maluna Creek drainage basin located in the Hunter Valley, New South Wales, Australia, for the period 1971‐86. the impact of viticulture, which commenced at Maluna in 1971, was studied using erosion plots, with caesium‐137 as an indicator of both soil erosion and sedimentation. Two methods were used to estimate vineyard soil losses from caesium‐137 measurements. Sediment output from the catchment was measured for three years, and extrapolated from readings taken at a nearby long‐term stream flow gauging station for the remaining 13 years. Relative amounts of soil loss from forest (60 per cent basin area), grazing land (30 per cent) and vineyards (10 per cent) were calculated. Soil losses by rain splash detachment were ten times greater from bare/cultivated sufaces than from the forest. Erosion plots of area 2 m2 showed no significant differences in soil loss between forest and grassland but, under bare soil, losses were 100 times greater. the 137Cs method was employed to calculate net soil loss from all vineyard blocks using both a previously established calibration curve and a proportional model. the latter method gave estimates of soil loss which were 3‐9 times greater than by the calibration curve, and indicated that average soil losses from the vineyard were equivalent to 62 t ha−1 y−1 (1971‐86). It was estimated that the forest contributed 1‐8 per cent, the grazing land 1.6 per cent, and the vineyard 96.6 per cent of the total soil loss during that period. Sediment storages within the fluvial system adjacent to the vineyard ws 9460 t for the period, whereas sediment output was equivalent to 215 t km−1 y−1. Independent measurements of soil erosion, storage, and output showed that 56 per cent of the eroded sediment remained in the catchment, and 34 per cent was transported out by Maluna Creek. the budget was able to be balanced to within 10 per cent.
Flow frequency responses to hardwood‐to‐grass conversion and subsequent succession
Authors: Burt T. P. , Swank W. T. 
Published: February 2007

AbstractA 8.9 ha (22 acre) catchment at the Coweeta Hydrologic Laboratory in western North Carolina was cleared of hardwood forest in 1958 and 1959 and seeded to Kentucky 31 fescue grass in 1959 and 1960. Grass production was high in years when fertilizer was applied and water yield was very similar to that expected from the original forest cover. as grass production declined, so water yields rose, with important increases in the magnitude of both low frequency flows and, particularly, in baseflow. in 1967 and 1968, when all vegetation was deadened in the catchment, the discharge levels in all flow frequency classes were higher. Natural revegetation was then allowed and water yields gradually declined towards the expected level, although there remained a tendency for winter flows to remain higher, and for summer flows to be lower than expected. This paper updates the earlier work of Hibbert (1969) and uses flow duration curves to extend his results.
Particle size characteristics of suspended and bed sediments in the rhône river
Authors: Santiago S. , Thomas R. L. , McCarthy L. , Loizeau J. L. , Larbaigt G. , Corvi C. , Rossel D. , Tarradellas J. , Vernet J. P. 
Published: February 2007

AbstractTen large volume water samples were taken from the Rhône River (Switzerland‐France) in November, 1989 for recovery of total suspended sediment by continuous flow centrifugation. the samples were freeze‐dried and analysed for particle size, organic carbon, total nitrogen, and carbonate. for comparative purposes, four bed sediments collected in July, 1989 are also described. the Rhône can be subdivided into three sections on the basis of the origins of the water. the first section is the Upper Rhône River draining into Lake Geneva. Waters are derived from glaciers, with low temperature and conductivity and high turbidity. Suspended sediment is coarse, has a bimodal distribution, and is low in both organic matter and carbonate. the second reach is from Lake Geneva to the confluence with the Saône at Lyon and has warmer water with higher conductivity and very low turbidity. Suspended sediment is higher in organic matter, with high carbonate originating from the lake. the final section is from Lyon to Arles, with warmer water and higher conductivity and turbidity due to modification by the Saône. Sediment is rich in organic matter, which May, account for an observed decline in oxygen in the river waters downstream from Lyon. Carbonate in these sediments also decreases due to increased turbidity from the Saône. Suspended sediments other than from the Upper Rhône show a remarkable consistency in grain size, predominantly in the fine silts (mode 9‐11 μm). This consistency indicates a high degree of suitability for geochemical analysis. Bed sediments were bimodal throughout, with a dominant coarse population in two out of the four samples. Grain size statistical parameters could be easily explained by application of the theory of mixing of two major populations in the sand size (bed traction load) and the fine silt/clay size (suspended sediment load).
Subsurface flow simulation of a small plot at loch chon, Scotland
Authors: Koide S. , Wheater H. S. 
Published: February 2007

AbstractSubsurface flow through a small forested hillslope plot in central Scotland has been studied by simulating the flow dynamics using a two‐dimensional saturated‐unsaturated subsurface flow finite element model. Parameter calibration based on the extensive hydrological data available at plot scale, has been performed using various search strategies and alternative objective functions. Good soil water potential simulations were obtained for mainly saturated events, although the simulated throughflows were significantly overestimated. the simulation of unsaturated events was less satisfactory. Throughflow overestimation May, reflect measurement uncertainty, but is also consistent with the effects of macroporosity.
Three‐dimensional modelling of hillslope hydrology
Authors: Binley Andrew , Beven Keith 
Published: February 2007

AbstractPhysically‐based models of catchment hydrology are computationally demanding. the cost of even small scale simulations of multidimensional subsurface flow problems is often considered too high and yet May, be important if one is to appreciate the complex flow pathways in heterogeneous catchments. This is likely to be the case for problems concerned with transport of chemical substances in soils, in particular those with some localized origin. Recent advances in computer hardware technology and numerical algorithms are beginning to make detailed simulations more feasible. We discuss here issues relating to using these new tools in modelling hillslope flow processes and document an example three‐dimensional simulation of a heterogeneous Darcian headwater.
Modelling soil water dynamics in a forest ecosystem. II: Evaluation of spatial variation of soil profiles
Authors: Bouten W. , Witter J. V. 
Published: February 2007

AbstractThis paper is the second in a series of three papers, dealing with the hydrology of a forested lowland catchment, within the context of soil acidification research. the hydrological behaviour of the unsaturated soil zone is described with the numerical simulation model SWIF. the first paper presents a site specific model calibration and discusses the implications of the hydrological behaviour for soil acidification (Bouten et al., 1992). the present paper deals with the extension of the model results from one specific site to a larger research area. a third paper gives a model description and discusses its numerical behaviour (Tiktak and Bouten, 1992).In order to evaluate the effects of the field variability of soil horizon thicknesses, the model SWIF is validated by using measured groundwater table dynamics of three sites, each having different soil horizon thicknesses. Subsequently, a sensitivity analysis is carried out in order to select the location‐dependent model parameters that cause the main variation in hydrological behaviour. Finally, the spatial patterns of model results and of the location‐dependent model parameters are compared.The drainage depth and the depth of the boundary between the sandy top soil and the underlying boulder clay appear to be the key parameters that cause large differences in transpiration and in the vertical distribution of root water uptake and soil water fluxes. Spatial patterns of model results, therefore, also show resemblance with the spatial patterns of these location‐dependent model parameters.Simulation results for a reference location with averaged soil horizon thicknesses turn out to be beyond the 90 per cent confidence interval of the areal mean model results. This emphasizes the necessity to simulate first and then average.
Effects of lithology and land use on storm run‐off in east luxembourg
Authors: Hendriks Martin R. 
Published: February 2007

AbstractFor a large part of the year, the forested catchments in the Keuper formation of east Luxembourg produce more direct run‐off on a storm basis than paired cultivated catchments. The occurrence of shrinkage cracks, their pronounced opening and closing, and the occurrence of natural pipes in the forested environment play a major role in explaining this phenomenon. The effect of land use on storm run‐off is studied in relation to that found for lithology in the same area.
Spatial and temporal mapping of water in soil by magnetic resonance imaging
Authors: Amin M. H. G. , Chorley R. J. , Richards K. S. , Bache B. W. , Hall L. D. , Carpenter T. A. 
Published: February 2007

AbstractExperiments on model and real soil blocks designed to assess the feasibility of using magnetic resonance imaging for three‐dimensional mapping of the time‐varying spatial distribution of water in structured soils are reported. The results show that, notwithstanding inherent problems in imaging natural soils with a significant iron content, experimental parameters can be identified which allow satisfactory images to be obtained. Magnetic resonance imaging may therefore provide important information on soil structure and water movement in dual porosity soils, with attendant benefits for the calibration of models of non‐Darcian flow in such soils.
Soil erosion and conservation on land cultivated and drained for afforestation
Authors: Carling P. A. , Glaister M. S. , Flintham T. P. 
Published: February 2007

AbstractErosion of soil from pre‐afforestation plough furrows has been measured on four soil types in Scotland for 12 to 18 month periods between 1987 and 1990. Rainfall‐run‐off was also measured at one site. Run‐off is directly proportional to furrow length and rainfall intensity, and for a wide range of intensities (typically > 6 mm hr−1) small amount of soil is flushed out of the furrows. However, for furrow spacings of 3.8 m, a critical downslope run‐off increment associated with significant soil loss is of the order of 25 cm3 s−1 m−1, which is in accord with a storm of five years return period and a maximum intensity of 25 mm hr−1. The total run‐off volume for any hydrograph is commensurate with the total rainfall in the rainstorm — typically 40–80% by the hydrograph peak and approaching 100% by the end of the hydrograph; i.e. long term storage is negligible. A positive relationship was recorded between furrow length, slope angle and sediment yield, with deposition predominating in furrows less than 30 m in length on slopes less than a few degrees. Soil loss is proportional to the excess streampower expended by the run‐off with an exponent in the range 1–1.5. For the soils examined, significant differences in soil loss when comparing sites for low power expenditure become undifferentiated at high power expenditures. For the rainfall regimes monitored, maximum soil losses were in the region of 40 kg per meter run‐length of furrow, when soil peds were ripped from the bed. Laboratory data concerning the critical erosion threshold power and shear stress to erode soil peds are in general accord with the threshold furrow run‐lengths defined using the field data for a five year storm and the soil losses observed.
Sediment source tracing using environmental magnetism: A new approach with examples from Australia
Authors: Caitcheon G. G. 
Published: February 2007

AbstractEnvironmental magnetism can be used for sediment source tracing in situations such as stream junctions where two catchments deliver magnetically distinguishable, well combined average source mixes to a trunk stream. Consistent mineral magnetic parameter relationships show that spatially and temporally constant magnetic mineral assemblages occur along reaches of natural streams. For most of the confluence mixing situations examined it is possible to distinguish between tributaries using magnetic parameter relationships. Using these relationships, relative tributary contributions to the resultant downstream mix can be quantified. The method can be used for tracing suspended and bedload sediments so that the principal source catchments can be determined by a sequence of measurements at stream junctions along a drainage network. There is considerable potential for using this new and easily applied method for studies of sediment delivery processes and sediment movement in fluvial environments.
Effect of mining and related activities on the sediment trace element geochemistry of lake coeur D'Alene, idaho, USA. Part I: Surface sediments
Authors: Horowitz Arthur J. , Elrick Kent A. , Cook Robert B. 
Published: February 2007

AbstractDuring the summer of 1989 surface sediment samples were collected in Lake Coeur d'Alene, the Coeur d'Alene River and the St Joe River, Idaho, at a density of approximately one sample per square kilometre. Additional samples were collected from the banks of the South Fork of the Coeur d'Alene and the Coeur d'Alene Rivers in 1991. All the samples were collected to determine trace element concentrations, partitioning and distribution patterns, and to relate them to mining, mining related and discharge operations that have occurred in the Coeur d'Alene district since the 1880s, some of which are ongoing.Most of the surface sediments in Lake Coeur d'Alene north of Conkling Point and Carey Bay are substantially enriched in Ag, As, Cu, Cd, Hg, Pb, Sb and Zn relative to unaffected sediments in the southern portion of the lake near the St Joe River. All the trace element enriched sediments are extremely fine grained (mean grain sizes « 63 μm). Most of the enriched trace elements, based on both the chemical analyses of separated heavy and light mineral fractions and a two step sequential extraction procedure, are associated with an operationally defined Fe oxide phase; much smaller percentages are associated either with operationally defined organics/sulphides or refractory phases.The presence, concentration and distribution of the Fe oxides and heavy minerals indicates that a substantial portion of the enriched trace elements are probably coming from the Coeur d'Alene River, which is serving as a point source. Within the lake, this relatively simple point source pattern is complicated by a combination of (1) the formation of trace element rich authigenic Fe oxides that appear to have reprecipitated from material solubilized from anoxic bed sediments and (2) physical remobilization by currents and wind driven waves. The processes that have caused the trace element enrichment in the surface sediments of Lake Coeur d'Alene are likely to continue for the foreseeable future.
Aquatic weed growth and flow resistance: Influence on the relationship between discharge and stage over a 25 year river gauging station record
Authors: Gurnell Angela M. , Midgley Peter 
Published: February 2007

AbstractIn developing a method for establishing reliable flow estimates from monthly current metered discharge measurements and continuous stage records at a site subject to seasonal aquatic weed growth, a 25 year series of estimates of the resistance of the channel to flow was generated. Analysis of this data set produced estimated relationships between flow resistance, discharge and stage which support the models developed from shorter term research investigations. In addition, the annual cycle in flow resistance at the section studied was found to range from a minimum resistance in January to a maximum in August and September.
Differences in oxygen‐18 content of throughfall and rainfall in hardwood and coniferous forests
Authors: Dewalle David R. , Swistock Bryan R. 
Published: February 2007

AbstractThe differences between δ18O in throughfall and open rainfall were studied for 16 selected spring and summer storms in deciduous, pine and spruce forests in central Pennsylvania, USA. Throughfall δ18O averaged 0.17, 0.32 and 0.24%o greater than δ18O of open rainfall for all storms at the deciduous, pine and spruce sites, respectively. Throughfall 18O enrichment was greater in low intensity spring rainfall events than higher intensity growing season storms and greater in the coniferous stands than the deciduous hardwood stand. Maximum throughfall 18O enrichment of l.61%o occurred in the spruce forest during one spring event. The differences between rainfall and throughfall 18O observed in this study for individual storm events may have important implications for isotope flow separation studies.
Water balance modelling in lateritic terrain
Authors: Langsholt Elin 
Published: February 2007

AbstractAn analytical approximate model for unsaturated flow in a spatially variable field, coupled with infiltration and evapotranspiration at the upper boundary and a fluctuating water‐table at the lower boundary, has been developed. The unsaturated flow equations depend on parameterizations of θ(Φ) and K(Φ). They are based on the notion of a moving, discontinuous front. The field heterogeneity refers to saturated hydraulic conductivity only. Horizontal variability is considered, and the flow medium is approximated as a set of uncorrelated, vertically homogeneous columns. Expectations and variances obtained with this approach have been compared with observations of the field hydrological processes. Three important aspects of the hydrology in this lateritic terrain are rapid water‐table response, Hortonian surface runoff generation and soil suction variability. The stochastic conceptualization used explains to a high degree these characteristics, although some limitations are demonstrated.
In‐channel surficial fine‐grained sediment laminae. Part I: Physical characteristics and formational processes
Authors: Droppo I. G. , Stone M. 
Published: February 2007

AbstractAn in‐channel surficial depositional feature (surficial fine‐grained laminae) composed of loosely bound fine sediment deposited during low flow conditions has often been observed in river systems in south‐western Ontario. The physical characteristics of this feature have been determined by a direct observation image analysis system. This sediment consists primarily of flocculated fine‐grained material. The size distributions of surficial fine‐grained laminae and suspended sediment were not significantly different. Each distribution is bimodal in nature and shows a characteristic grain size deficiency in the 4‐5 μm size range. This observation suggests that flocculation and not low discharge or low competence is the dominant mechanism for the formation of surficial fine‐grained laminae under conditions of low flow in fluvial systems of south‐western Ontario. A quantitative assessment of this feature shows its potential importance as a source of fine‐grained sediment and associated contaminants for downstream transport.