bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design and application of a constant head well permeameter for shallow high saturated hydraulic conductivity soils
Authors: Bell R. W. , Schofield N. J. 
Published: February 2007

AbstractA new constant head well permeameter has been designed to measure saturated hydraulic conductivities (Ks) ranging from 10−6 to 10−3 ms−1. Application to shallow soils of Western Australia in this Ks range highlighted problems with different aspects of the borehole discharge response. Firstly steady‐state borehole discharge was only reached in 13 out of 50 tests conducted. This was a consequence of the constraint placed on the volume of water storage (40 L) of the permeameter. For some non‐steady‐state cases, techniques of estimating steady‐state discharge from the available data are examined. Secondly borehole discharge was observed to increase with time in 34 per cent of cases. A satisfactory physical explanation of this phenomenon is not presently available. Other limitations in the application of the constant head well permeameter are noted.Examination of a number of recent theoretical developments in the determination of Ks led to a preference of saturated‐unsaturated flow solutions by Philip (1985) and Reynolds et al. (1985). These solutions involve the ‘sorptive number’ to which the solutions were sensitive but not critically sensitive. The theory was used to establish design criteria for the permeameter and to identify an optimum application strategy in terms of well dimensions and heads. Error estimation indicated that the designed permeameter was a practically useful field instrument.
Hydrology of a headwater basin wetland: Groundwater discharge and wetland maintenance
Authors: Roulet Nigel T. 
Published: February 2007

AbstractThe link between groundwater and surface hydrology in a small headwater drainage basin in the zone of glacial deposition of southern Ontario south of the Precambrian Shield was examined for two years. The basin is situated in a discharge zone of a regional aquifer and contains a small treed spring‐fed swamp. The swamp exists because of the groundwater and has little effect on the maintenance of streamflow. Groundwater input to the swamp is an order of magnitude larger than precipitation. Groundwater of local and regional origin passes through the swamp by two routes: surface streamlets, where groundwater that emerges at specific seepage points in the swamp is conveyed over the ground surface with little interaction with the swamp itself, and by diffuse seepage in the swamp and through the bed of the stream. While the diffuse seepage input is the smaller component of groundwater it maintains the swamp's saturation. Groundwater input to the swamp from the specific seepage points and diffuse flow varies little over a year; therefore the saturation of the swamp and baseflow from the basin display little seasonal variation compared to other wetland types. The existence of the valley bottom in the headwater basin alters the seasonal and storm hydrology and is important to biogeochemical transformation of emerging groundwater.
A continental hydrological assessment of a new grid‐based digital elevation model of Australia
Authors: Hutchinson M. F. , Dowling T. I. 
Published: February 2007

AbstractA rectangular grid digital elevation model (DEM) for Australia, with a horizontal resolution of 1/40 degree of latitude and longitude (approximately 2.5 km), has recently been calculated from continent‐wide coverages of point elevation and stream line data using an elevation gridding technique which incorporates a drainage enforcement algorithm. An automated drainage basin analysis of this DEM is in close agreement with existing basin analyses, both for the better surveyed coastal areas with well‐defined relief, and for large areas of low relief that make up much of the interior Lake Eyre basin and the Murray‐Darling basin. The analysis of the arid western plateau region differs from the currently accepted analysis but is in broad agreement with a previous analysis of palaeodrainage systems based on topographic and geological information. The drainage analyses is used to calculate cumulative distributions of spatially distributed, hydrologically significant, terrain parameters for the Murray‐Darling and Derwent River basins. The adequacy of the resolution of the DEM for continental hydrological analyses is assessed by comparing drainage basin analyses and cumulative distributions of terrain parameters at resolutions of 1/40th and 1/20th degree of latitude and longitude.
Terrain analysis for urban stormwater modelling
Authors: Djokic Dean , Maidment David R. 
Published: February 2007

AbstractA geographic information system (ARC/INFO) is used to develop a model of the urban environment for storm drainage analysis. The drainage system is divided into surface terrain, stormwater intakes, and the drainage network. The intakes hydrologically connect surface and subsurface flow elements. The drainage network consists of both man‐made structures (pipes and channels) and overland flow paths that connect them. The land surface terrain is defined by a triangulated irregular network (TIN), which is used to determine necessary parameters for design flow calculations. Each of the three basic elements of the urban terrain representation, inlets‐defined as points, drainage network‐defined as lines, and surface terrain‐defined as TINs, has its own specific data structure. The three databases are fully integrated, and the stored information is used to determine whether inlets and pipes can convey 10‐and 25‐year design flows, using the rational method.An ‘intelligent network builder’, is developed using the Nexpert Object expert system shell, to test for completeness of databases and flow paths prior to hydrological computations. If necesssary, the intelligent network builder starts up ARC/INFO procedures that fill in missing links in the drainage network and missing flow properties of its components. An example application is made to the drainage system of a section of City of Asheville, North Carolina.
Hydrological consequences of artificial drainage of grassland
Authors: Armstrong Adrian C. , Garwood E. A. 
Published: February 2007

AbstractSoil water regimes and water balances are presented for a series of drained and undrained experimental grassland plots, intended to examine the agronomic consequences of drainage. Although drainage has lowered the watertables and reduced the duration of waterlogging in the drained plots, its effects in terms either of the total water quantities leaving the site or of peak flows is quite small. The major effect of drainage is to alter the route of water loss from the site. In its undrained state, the soil is waterlogged for the majority of the winter, incident rainfall cannot infiltrate, and water leaves as surface runoff or near‐surface flow. The introduction of fissures by mole drainage both provides an outlet and enhances the macroporosity, so that the rain moves rapidly through the soil and appears as drainflow. Consequently, the additional delay in generating peak runoff through the drainage system is only of the order of 30 minutes on this site.
Use of a single‐bowl continuous‐flow centrifuge for dewatering suspended sediments: Effect on sediment physical and chemical characteristics
Authors: Rees Terry F. , Leenheer Jerry A. , Ranville James F. 
Published: February 2007

AbstractThe use of a single‐bowl continuous‐flow centrifuge (CFC, Sharples‐Pennwalt Model AS‐12) for dewatering suspended sediment from large volumes of river water is evaluated. Sediment‐recovery efficiency of 86‐91 per cent is comparable to that of other types of CFC units. The recovery efficiency is limited by the particle‐size distribution of the feed water and by the limiting particle diameter that is retained in the centrifuge bowl. The limiting particle diameter, using the parameters for this study (bowl radius = 10.5cm; bowl length = 71.1 cm; rotational velocity = 16000 r min−1; flow rate = 2 L min−1, and an assumed hydrated particle density = 1.7 gm cm−3), is 370 nm. There seems to be no particle‐size fractionation within the centrifuge bowl—the median particle size was the same at the top as at the bottom. Particle electrophoretic mobility plays some role in fractionation of particles within the centrifuge. The mobility ranged from −1.19 to −2.01 × 10−8 m2 V−1 s−1, which is typical of clays coated with organic matter, the charge of which is partially neutralized by divalent cations and iron. Contamination by trace metals and organics is minimized by coating all surfaces that come in contact with the sample with either FEP or PFA Teflon and using a removable FEP Teflon liner in the centrifuge bowl. Because of the physical and chemical factors affecting particle fractionation within the centrifuge, care must be exercised in interpreting the environmental consequences of particles collected by continuous‐flow centrifugation.
IV: EPSAT‐NIGER study of rainfall over the Sahel at small time steps using a dense network of recording raingauges
Authors: Thauvin V. , Lebel T. 
Published: February 2007

AbstractThe high density, static memory raingauge network of the EPSAT‐NIGER experiment was designed with the aim of: (1) studying the rainfall spatial variability in the Sahel, as may be seen from ground networks of varying density, and (2) providing reference values for the calibration of a C band radar system. A first subset of 37 raingauges was installed in 1988 and the remaining 43 in 1989, thus providing a network of 80 stations, spread over a 100 × 100 km square area. The data analysis is based on the indentification of the structural function for each rainfall event. This permits classification of the events into three main categories with respect to their spatial organization. Furthermore the differences between the shower body and the trail are important and it is shown that the analysis of the spatial organization at the event scale may not be applicable to the calibration of high temporal resolution radar data. Estimation of the areal rainfall over two reference areas is also carried out.
V: Daily catchment rainfall estimated from meteosat
Authors: Dugdale G. , Hardy S. , Milford J. R. 
Published: February 2007

AbstractMeteosat data for 1986 to 1988 have been used to estimate the daily rainfall over catchments of tributaries of the river Senegal in Mail and Guinea. The technique uses the methodology of the TAMSAT group of the University of Reading, which involves the selection of an appropriate cloud top temperature threshold to determine whether the cloud is producing rain and the rainfall is estimated from the period during which storm clouds remain over a site. After calibration against all available raingauges in the catchments, the daily rainfall estimates derived by this technique were used as inputs to rainfall‐runoff models. The results indicate that the streamflow models, which had themselves been calibrated using raingauge data, performed as well or better when the satellite derived estimates were used as inputs than when gauge data were used. An economical, automated operational system is described.
A model of dissolved organic carbon concentrations in soil and stream waters
Authors: Grieve Ian. C. 
Published: February 2007

AbstractThe release of dissolved organic carbon (DOC) into drainage waters was modelled using the hydrology of the Birkenes model of stream water chemistry and estimated parameters for the formation and decay of soluble organic matter in the soil. The model was first tested against soil water DOC concentrations over a three year period in the Loch Dee catchment in southwest Scotland. It predicted annual cycles in DOC at one site, but underestimated maximum DOC in the first year, overestimated in the following year, and predicted values very similar to the measured values in the third year. With small modifications to the parameters controlling organic matter addition and decay it successfully predicted DOC variations at two other soil water sites with smaller mean DOC.Further tests were made against short‐term DOC variations in a stream draining a subcatchment of Loch Ard in west‐central Scotland, using the same decay and addition parameters. Prediction of temporal variation was good, although predicted concentrations were about 25 per cent less than measured values. Considerable potential for the use of fully optimized models of DOC production in soil and stream waters is identified on the basis of these results.
Estimation of soil moisture status using near infrared reflectance
Authors: Whalley W. R. , Leeds‐Harrison P. B. , Bowman G. E. 
Published: February 2007

AbstractThe use of a prototype near infrared reflectance meter for estimating the water content of soil is described. The instrument, developed from one used for estimating the water content of forage is based on the measurement of reflectance of infrared light emitted at wavelengths of 1450 nm, a strong water absorption band, and 1300 nm a weak water absorption band. Calibration curves of reflectance and reflectance ratio versus moisture content for pure sands and sand/clay mixes are presented. Problems associated with the measurement of moisture content using this technique on swelling soils are highlighted. The use of a modified form of this instrument for estimating soil moisture status in the field is discussed.
Water repellency in a dry sclerophyll eucalypt forest — measurements and processes
Authors: Crockford H. , Topalidis S. , Richardson D. P. 
Published: February 2007

AbstractThe magnitude of soil water repellency in a dry sclerophyll eucalypt forest was measured periodically over four years. The varying responses from a range of sites within the forest are discussed and the effect of amount and frequency of rainfall is shown.It was found that some weeks of consistently wet weather were required for water repellency breakdown, and a frequency of rainfall much greater than normal in the study area for it to remain broken down. Even after an extended period of breakdown, it was found that repellency can be reestablished after one week of hot dry weather.Laboratory tests were used to examine the major repellency processes; three were identified and the relative importance of each considered in the context of the field study. The relative influence of each depended on the physical and chemical characteristics of the sites.The repellent soil samples were more repellent to water of throughfall origin, and even more repellent to stemflow than to distilled water. The repellency response also varied with the type of vegetative cover present. The influence of these phenomena on the preservation of water repellency and the relevance of repellency in macropore infiltration processes are discussed.
Measurement and prediction of water movement in a field soil: The matrix‐macropore dichotomy
Authors: Smettem K. R. J. , Ross P. J. 
Published: February 2007

AbstractThe saturated and unsaturated flow properties of a field soil under two tillage treatments were obtained with ponded rings and disc permeameters of dissimilar radii. No difference was observed between tillage treatments but the flow properties displayed a distinct macropore‐matrix dichotomy, with K changing by an order of magnitude as ψ0 went from just ‐ 30 mm to zero.Accurate prediction of time to incipient ponding was achieved using both numerical and analytical models calibrated with field hydraulic properties that were characteristic of the soil matrix. However, extension of the numerical model to the prediction of the wetting front development under non‐ponded conditions was less accurate due to localized preferred wettingIt is hypothesized that at this site, localized concentration of rainfall and hence, preferred wetting, May, occur by interception and stemflow associated with lines of standing stubble present in the original seeding slots.
A water balance study in lateritic terrain
Authors: Langsholt Elin 
Published: February 2007

AbstractThe water balance of a 600 m2field site on a lateritic hillslope in Kerala, southwest India, has been studied during two southwest monsoon seasons. Surface runoff was of minor importance while infiltration and evapotranspiration were the major components amounting to approximately 2/3 and 1/3 of the rainfall, respectively. Groundwater response was rapid, involving fluctuations of several metres. Recharge mechanisms hypothesized are water movement via preferred pathways from the ground surface to the capillary fringe where rapid rise in groundwater level is brought about by a transmitted pressure pulse. Groundwater recharge was found normally to take place during the southwest monsoon season only. the field study demonstrates that seasonal shallow groundwater recharge representing the major portion of the rainfall May, be observed in this lateritic terrain in the humid tropics. It indicates a good potential for further groundwater development. Moreover, conditions are conducive to a considerable contribution to possible recharge to deeper aquifers. the observed groundwater recharge is the result of a complex process on which further research will throw more light.
Systematic parameter estimation of watershed acidification model
Authors: Chang Fi‐John , Delleur J. W. 
Published: February 2007

AbstractA joint strategy for parameter estimation which can systematically identify the important model parameters is presented. the strategy includes a regionalized sensitivity analysis (RSA) and an automatic parameter calibration technique (APCT). the RSA is based on a large number of Monte‐Carlo simulations to identify the sensitive parameters and to establish a range of appropriate values for each sensitive parameter. the APCT adjusts the values of the sensitive parameters based on changes in the residual variances between the predicted and observed values. the strategy is applied to the watershed acidification model—ILWAS. the strategy succeeds in identifying the sensitive parameter and increases the likelihood of obtaining a global optimal parameter set. Improvements in the model prediction of the streamflow and chemistry are obtained.
Hydraulic and salinity regime of two affected sites in the Yizre'el valley, Israel
Authors: Gafni Abraham , Salingar Yigal 
Published: February 2007

AbstractCauses of recent salinization of numerous plots in the Yizre'el Valley of Israel were examined through a detailed field study of two severely affected sites. in particular, the theory of artesian influence on salt build‐up in the upper cultivated soil layer was investigated. Two piezometer nests and 12 wells were installed to study the subsurface hydraulic regime. Water samples and soil extracts were taken to characterize the chemical composition down to 10m. No significant head differences were measured at the lower site, while at the upper site 96 per cent of the head that existed at the deep (7.5 m) artesian layer was dissipated within the overlying thick clay layer. Slight head differences were noted in the shallow layers. the deep‐lying, coarse‐textured aquifer differs markedly from the upper confining layers and constitutes an independent water body that has little relevance to surface processes. Chemical and hydrological analyses indicate that applied low‐quality irrigation waters May, be the primary cause of downward‐moving salinity and alkalinity which, in turn, affect soil permeability and site productivity.
An analysis of snow cover patterns in a small alpine catchment
Authors: Bl G.öschl , Kirnbauer R. 
Published: February 2007

AbstractSnow cover patterns in a 9.4 km2 basin in the Austrian Alps are examined during spring and summer 1989. Digital mono‐plotting from oblique aerophotographs is used for mapping. on the basis of a square grid with 25 m spacing, snow cover as mapped during nine surveys is analysed as a function of elevation and slope. During winter conditions the snow cover is found to be much better related to these terrain features than during the late ablation period.
A simple and inexpensive turbidity meter for the estimation of suspended sediment concentrations
Authors: Lawler Damian M. , Brown Robert M. 
Published: February 2007

AbstractThe relatively high cost of commercially available turbidity meters has inhibited detailed and intensive research on spatiotemporal patterns of suspended sediment transport. We describe here the electronic and physical design of an inexpensive turbidity sensor which is easy to construct, simple to interface with portable millivolt meters, dataloggers, computers, or chart recorders, consumes exceptionally small currents, and is robust and reliable. the very low individual cost allows a large number of sensors to be distributed throughout the water body of interest to facilitate turbidity mapping. Turbidity profilers to detect vertical or lateral turbidity changes in rivers, lakes, estuaries, or near‐shore zones are also shown to be feasible. Test data are presented from a highly turbid glacial river in southern Iceland.
Particle size characteristics of suspended sediment in Southern Ontario rivers tributary to the great lakes
Authors: Stone M. , Saunderson H. 
Published: February 2007

AbstractIn spite of the important relationship between sediment particle size and the transport/deposition of adsorbed pollutants in fluvial systems, little information regarding the size characteristics of suspended sediment transported by southern Ontario Great Lakes tributaries is currently available. This paper examines long‐term sediment and hydrometric data collected by the Water Resources Branch of Environment Canada in order to provide information on (1) typical particle size distributions of suspended sediment, (2) relationships between source material and particle size characteristics of suspended sediment, and (3) temporal variation in the particle size characteristics of suspended sediment from six southern Ontario rivers. Results illustrate the complex behaviour and variability of sediment particle size transport in these rivers and demonstrate the need for a better understanding of seasonal effects on sediment availability and conveyance processes in fluvial systems.
Caesium‐137 estimates of erosion in agricultural areas
Authors: Sutherland R. A. 
Published: February 2007

AbstractSediment redistribution within near‐level agricultural fields in the Gray Wooded soil zone of Saskatchewan was studied using the artificial environmental tracer caesium‐137 (137Cs). the objective of this study was to estimate erosion rates caused by wind erosion, and land clearing techniques (i.e. bulldozing). Net rates of erosion and deposition were quantified over the past 30 years on three fields. Wind erosion was estimated to be approximately 1.0 t ha−1y−1on a near‐level field, with 50 per cent of the sampling sites having erosion rates in excess of soil formation. Bulldozing produced median net sediment flux values of between 40 and 90 t ha−1y−1. in addition, between 65 and 85 per cent of the sampling sites had erosion rates in excess of the maximum tolerable limit (i.e. 11.0 t ha−1y−1). These results indicate significant accelerated erosion results from land clearing techniques used in central Saskatchewan. Bulldozing of the fields removed the LFH‐horizon and exposed the underlying mineral horizon. Bulk densitites of the 0 to 15 cm layer in the cleared fields were 27 to 55 per cent greater than the comparable depth increment within the undisturbed forest site. Organic carbon concentrations within the 1930s, 1979, and 1987 fields were decreased by 47, 42, and 37 per cent, respectively following cultivation and bulldozing. Decreases in total nitrogen for the cultivated fields ranged from 33 to 38 per cent.