bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic and salinity regime of two affected sites in the Yizre'el valley, Israel
Authors: Gafni Abraham , Salingar Yigal
Published: February 2007

Causes 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

Snow 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

The 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

In 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

Sediment 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.
DISTRIBUTED MODELS 7: A CIS APPROACH
Authors: Drayton R. S. , Wilde B. M. , Harris J. H. K.
Published: February 2007

A rainfall and run‐off model has been developed which is based on a rectangular grid cell network. the run‐off in each cell is estimated empirically and is routed through the network to the principal drainage lines. Information on the land cover in each 50 × 50 m cell is interpreted from remotely sensed data, gathered by an orbiting satellite. Values of topographic parameters for each cell are derived from a digital model of the terrain. Other more conventional data are acquired by digitizing maps. the large amounts of data required in this approach are handled by a geographical information system (GIS), which is a management system specially designed for data with spatial characteristics. a GIS has functions which allow the user to combine the many layers of data within the GIS arithmetically or logically to provide fresh information. At the current stage of development the GIS provides estimates of the United States Department of Agriculture Soil Conservation Service curve number for estimating the run‐off in each cell. an analysis of the digital terrain model defines the pathway taken by run‐off from each cell and the run‐off is routed from cell to cell as far as the principal drainage lines, where a conventional hydraulic analysis is used. the model benefits from a simple and robust approach to run‐off estimation distributed on a very fine grid. an important feature of the model is its ability to use historical satellite images to estimate changes in the catchment's response over a period of time. Future changes in land use May, also be easily incorporated into the GIS. the model is being tested on data from the Tywi catchment in West Wales, UK, which had undergone large changes in land cover due to forestation.
Modelling soil water dynamics in a forested ecosystem. I: A site specific evaluation
Authors: Bouten W. , Schaap M. G. , Bakker D. J. , Verstraten J. M.
Published: February 2007

Soil water dynamics in a forested lowland catchment are studied in order to support a research on biogeochemical processes and soil acidification in particular.

The numerical simulation model SWIF, describing soil water dynamics in forests, is calibrated and validated for a specific site by using three years of daily measurements of pressure head profiles. on the basis of model results, the hydrological behaviour of the forest system is discussed, with special attention to transpiration and to the vertical and temporal dynamics of soil water contents, root water uptake and soil water fluxes. as water uptake by oaks and beeches is restricted to the unsaturated soil zone, high groundwater tables in the rather poorly drained duplex soil appear to have a large impact on the soil water dynamics.

Suggestions are made on the implications of the hydrology for soil acidification. This discussion shows that a thorough knowledge of the hydrological behaviour of the system can greatly contribute to the understanding of biogeochemical processes and soil acidification.

This paper is the first in a series of three papers. the second discusses the possibilities of extrapolating model results from the calibration site to other locations within the research area, which have varying soil horizon thicknesses (Bouten and Witter, 1992). the third paper gives a full description of the model SWIF with some technical details. It also discusses its numerical behaviour (Tiktak and Bouten, 1992).
Modelling soil water dynamics in a forested ecosystem. III: Model description and evaluation of discretization
Authors: Tiktak A. , Bouten W.
Published: February 2007

The model SWIF (Soil Water in Forested ecosystems) is presented. SWIF is a model for the simulation of water flow in the unsaturated soil zone, including water extraction by roots and lateral saturated drainage. the model gives a halfimplicit finite difference solution to the flow equation. for minimizing computing time, the model chooses its integration time steps based on the rate of change of soil water conditions. the model is not a conceptually new model. However, it meets the requirements of an entirely modular programme in which new theories can easily be implemented. the hydrology of the canopy and the forest floor is described in independent modules.

Simulation results are evaluated in relation to temporal and vertical discretization, using a simulation of soil water dynamics in a forest over a period of two growing seasons. Both the site description and the simulation results are given in an accompanying paper (Bouten et al., 1992). in another paper a sensitivity analysis of the model is given (Bouten and Witter, 1992).

In order to evaluate the effects of temporal discretization of boundary condition's, the length of the interval of constant averaged boundary conditions was varied from one hour to one month. the simulated annual transpiration is found to be dependent on this interval for a wet year, but not for a dry year. When the boundary conditions are taken constant for intervals shorter than one day, simulated soil water contents show a highly dynamic behaviour during and directly after heavy rainfall. Then small integration time steps are required and computing time increases strongly.

For the evaluation of the effects of vertical discretization, the number of soil layers was varied from 5 to 40. the yearly transpiration appears to be almost independent of the layer thickness as long as the horizon boundaries are not altered, but the temporal distribution of transpiration and water contents are affected. the required computing time for the simulation of the water balance of a full growing season increases from 2.5 minutes for a simulation of five layers to 18 minutes for a simulation of 40 layers.

When model results are evaluated on a yearly basis, they appear to be not very sensitive to the temporal and vertical discretization. Only if research aims require more detailed model results on a shorter timescale, higher computing times are to be accepted.
Temporal and spatial variations of runoff and rainwash erosion on an agricultural field
Authors: Mathier L. , Roy A. G.
Published: February 2007

This paper investigates the spatial and temporal variations of runoff, erosion and rate of sediment transport on an agricultural field submitted to natural rainfalls. The site, located in the Eastern Townships (Québec, Canada), is a corn field (10000 m2) where sheetwash erosion is active. Water (Q) and sediment (Qs) discharges were measured from June to October at eight locations on the field and for ten rainfall events. Analysis of the data was carried out on an aggregate data set and on the distributed measurements in time and space. The results showed that changes in vegetation, soil compaction and crusting are critical in determining temporal variations of runoff and erosion. Until August, the increase in soil compaction reduced infiltration capacity and depression storage and generated greater runoff for a given rainfall intensity (I). Sediment transport decreased as particle detachment is less likely to occur when vegetation breaks the drop impact and the soil surface is sealed. Later in the season, we observed an increase in sediment concentration associated with the presence of burrowing insects and harvest activity, providing loose sediments to the broken down surface. Intercepts and slopes of the relationship between Q and Qs also vary during the period of measurement. High sediment availability over the soil surface in June and October gives high intercept values. The slope of the relationship is more stable but difficult to estimate for extreme events (high values of I or low Q values) where the number of sampled points are small. During a rainfall, the response of the field is dominated by the topography and drainage area. The largest amount of runoff and erosion occurred on straight and steep slopes with small drainage areas, and on converging gentle slopes with large drainage areas. Although aggregate runoff and erosion values are decreasing with drainage area, parameters of the Qs‐Q relationship for different locations on the field are not statistically different. These results bear important consequences for models of sheetwash erosion on agricultural fields.
Longer‐term water temperature behaviour in an upland stream
Authors: Webb B. W. , Walling D. E.
Published: February 2007

Water temperature behaviour in a small upland Exmoor catchment (the Black Ball Stream) has been studied over a 14‐year period since January 1976. Results from continuous records revealed annual mean stream temperatures to have a coefficient of variation of less than 5 per cent, and values of 5,10 and 15°C to be equalled or exceeded 90,41.8 and 4 per cent of the time respectively. The annual regime of water temperature was relatively predictable but diel cycles of varying magnitude were superimposed on the seasonal march. A clear seasonal hysteresis was evident whereby diel range in spring exceeded that in autumn by typically more than 2°C. Trend analysis of monthly temperature time series highlighted the stability of the thermal regime in recent years, although investigation of air‐water temperature relationships indicated that an increase in mean surface air temperature projected for southwest England by the Year 2050 would result in a rise of mean winter and summer stream temperatures by 1.6 and 1.3°C respectively. Analysis of streamflow effects on water temperature suggested that future indirect impacts of climatic change on thermal regime via changes in stream discharge are likely to be minor.
Sensitivity analysis on processes affecting bypass flow
Authors: Booltink H. W. G. , Bouma J.
Published: February 2007

Bypass flow in structured soils is dominated by soil hydrological processes, such as rain intensity, initial pressure head of the soil, surface storage of rain, horizontal contact area and absorption rate, and hydraulic conductivity of the soil matrix. This study was conducted to determine the relative impact of these processes in different soil types. A quasi 3‐dimensional simulation model was used to calculate the effects of these soil hydrological input parameters on surface infiltration, macropore flow (with related horizontal absorption) and drainage. For light textured soils, surface infiltration was the most important term in the water balance. Heavy textured soils, in contrast, had drainage as the main term. In the latter soils bypass flow, when occurring, was almost equal to the amount of rain applied, indicating that absorption processes were strongly reduced. Lateral absorption on macropore walls was a minor fraction in the total mass balances, due to limited contact area and relatively weak diffusivity forces. Surface infiltration is a crucial parameter in bypass flow and is mainly dependent on rain intensity, initial pressure head and conductivity of the soil matrix. This requires measurement methods for hydraulic conductivity that specifically consider the effect of macropores.
A gis‐based distributed parameter hydrologic model for urban areas
Authors: Smith Michael B.
Published: February 2007

A hydrologic model for urban areas has been developed which incorporates distributed parameter modelling concepts and functions in the context of a geographic information system. In the proposed model, the watershed is represented as a cascade of grid cells, whose size can be specified by the user. Preliminary processing includes the determination of overland flow directions for each cell. An automated procedure is used to establish the cell‐to‐cell connectivity scheme, which is used to order the computations within each time step. Infiltration is computed using the Green‐Ampt equation, while runoff rates are computed using a coupling of the continuity equation and Manning's equation for turbulent flow. Storm sewer flows are routed using time‐shift routing. The model is capable of simulating flow through streets and offers the possibility of predicting the downstream movement of sewer system overflows. In preliminary testing on a small residential watershed, the model was able to reproduce measured hydrographs.
Obtaining basic simulation data for a heterogeneous field with stratified marine soils
Authors: Finke P. A. , Bosma W. J. P.
Published: February 2007

Thinly stratified sedimentary deposits in a heterogeneous field were investigated to obtain basic physical data for the simulation of water flow. A procedure is described which translates a thinly stratified soil profile into a number of functional layers using functional hydrological properties. A functional layer is defined as a combination of one or more soil horizons and should (i) be recognizable during a soil survey using an auger and (ii) show significantly different functional hydrological properties when compared with another functional layer. This procedure gave three easily recognizable functional layers. Sets of hydrological characteristics of these three functional layers were obtained by physical measurements of the soil and by estimation, using textural data for classification into a standard Dutch series. The performance of several combinations of these sets was tested by comparing simulated and measured soil matric potentials for seven plots during one year. The best simulation results were obtained if measured soil hydraulic characteristics were used for relatively homogeneous functional layers and if the soil hydraulic characteristics were estimated at each location for the most heterogeneous layer.
II. Snow hydrology processes and remote sensing
Authors: Rango Albert
Published: February 2007

In the last 20 years remote sensing research has led to significant progress in monitoring and measuring certain snow hydrology processes. Snow distribution in a drainage basin can be adequately assessed by visible sensors. Although there are still some interpretation problems, the NOAA‐AVHRR sensor can provide frequent views of the areal snow cover in a basin, and snow cover maps are produced operationally by the National Weather Service on about 3000 drainage basins in North America. Measurement of snow accumulation or snow water equivalent with microwave remote sensing has great potential because of the capabilities for depth penetration, all‐weather observation and night‐time viewing. Several critical areas of research remain, namely, the acquisition of snow grain size information for input to microwave models and improvement in passive microwave resolution from space. Methods that combine both airborne gamma ray and visible satellite remote sensing of the snowpack with field measurements also hold promise for determining areal snow water equivalent. Some remote sensing techniques can also be used to detect different stages of snow metamorphism. Various aspects of snowpack ripening can be detected using microwave and thermal infra‐red capabilities. The capabilities for measurement of snow albedo and surface temperature have direct application in both snow metamorphism and snowpack energy balance studies. The potentially most profitable research area here is the study of the bidirectional reflectance distribution function to improve snow albedo measurements. Most of the remote sensing capabilities in snow hydrology have been developed for improving snowmelt‐run‐off forecasting. Most applications have used the input of snow cover extent to deterministic models, both of the degree day and energy balance types. Snowmelt‐run‐off forecasts using satellite derived snow cover depletion curves and the models have been successfully made. As the extraction of additional snow cover characteristics becomes possible, remote sensing will have an even greater impact on snow hydrology. Important remote sensing capabilities will become available in the next 20 years through space platform observing systems that will improve our capability to observe the snowpack on an operational basis.
Sensitivity of bocage landscapes to surfaces run‐off: Application of the kirkby index
Authors: Merot Ph. , Bruneau P.
Published: February 2007

The Breton bocage is a landscape of fields enclosed by a network of hedgerow banks and ditches. Organization of this bocage varies considerably in different areas of Brittany. However, one constant feature of the different bocage landscapes is the presence of banks enclosing bottom lands, which enclose elongated plots in the thalweg bottoms. The banks enclosing the bottom lands influence the sensitivity of the basin to surface run‐off and also the presence of excess surface water zones. To analyse the part played by banks enclosing bottom lands, the topography of a typical first order basin was modelled and the existence of such a bank within the catchment was simulated. The effect of the bank on the Kirkby index, a topographical parameter defining the sensitivity of soils to surface run‐off was analysed. Modification of its spatial distribution is considerable for mean values of the index. The saturation zone, the storm run‐off source area, is reduced to that area of bottom land enclosed by the bank; it thus varies very little so that run‐off conditions are almost constant whatever the climatic conditions. From the methodological point of view, the interest of analysing the spatial distribution of morphometric parameters of a catchment may be noted; in the example studied, the heterogeneity of the Kirkby index distribution is an important factor in the analysis.
Melt water chemistry and its impact on stream water quality
Authors: Jenkins Alan , Ferrier Robert , Waters David
Published: February 2007

Samples of snowpack leachate were collected over a 60 day period of the spring melt season in 1988 and 1989 at a 10 km2 upland catchment in the Cairngorm mountains of Scotland. These were analysed for major ions to assess snowpack chemistry dynamics through the spring and to assess the melt water influence on stream water chemistry. The data clearly show preferential elution of sulphate and nitrate over chloride and hydrogen over the other cations during the early melt of 1988. Following the addition of ions to the snow surface, either as snow or later in the season as rain, the elution sequence is reproduced. Comparison of leachate chemistry with stream chemistry samples taken at the basin outlet indicate that snow pack melt water contributes directly to stream water. The stream water chemistry signal is, however, noisy and the stream concentrations are considerably damped relative to the snowpack leachate. This is thought to be a consequence of differential melting within the catchment as the snowpack at lower altitudes is at a more advanced stage of melt and so holds fewer solutes and mixing with groundwater contributions. Temperature observations at different altitudes within the catchment support this interpretation.
The calibration and use of pressure transducers in tensiometer systems
Authors: Hoelscher James R. , Nuttle William K. , Harvey Judson W.
Published: February 2007

The uncertainty in a transducer/tensiometer system was assessed with temperature and pressure calibrations. A reference transducer/tensiometer pair was used to factor out temperature related deviations from two monitoring pairs. The reference pair removed most of the deviations, resulting in a high estimate of precision. In contrast to earlier reports of high accuracy, these estimates of accuracy were considerably reduced by a time correlated residual pattern. The calibrations suggested that the electronic components may be responsible for these residual errors and illustrated the need for experimentation which isolates the error among groups of components. The complexity of transducer/tensiometer networks, and the differing response of each component to thermal loading, demonstrated the necessity of using a reference system, which when properly designed can yield reliable pressure readings for soil water.
Analysis of storm run‐off sources using oxygen‐18 in a headwater swamp
Authors: Hill A. R. , Waddington J. M.
Published: February 2007

A combination of hydrometric data and observations of natural isotope (oxygen‐18) variations in saturation overland flow and stream discharge were used to investigate the sources of storm run‐off in a headwater swamp located in a permanent groundwater discharge zone near Toronto, Canada. The results of a two‐component hydrograph separation indicated that pre‐event water formed 80–90% of the stream hydrograph volume for six of the seven storms analyzed in June–November 1990. However, the instantaneous event water contribution showed considerable variability, ranging from maximum values of 20–25% for four moderate intensity storms to 63% for a high intensity thunderstorm with a return period of two years. The relative contribution of event and pre‐event water to storm run‐off from saturated areas and small streamlets within the swamp was similar to the main outlet stream. The dominance of pre‐event water during storms could be accounted for by the mixing of a small volume of event water with a large pool of pre‐event water on the surface of permanently saturated areas within the swamp. Occasional storms of high intensity or long duration produced a greater shift towards an event water signature in the saturated areas and a larger event water contribution to the outlet stream hydrograph.
Design of stable drainage networks in upland forestry plantations
Authors: Flintham T. P. , Carling P. A.
Published: February 2007

Erosion of man‐made, forestry drainage channels occurs when the plough cuts through the surface peat layer into the underlying erodible mineral soil. A procedure is developed, based on hydraulic considerations, which will allow the drainage engineer to design stable drainage networks in upland forestry plantations. An example design chart is given for an erodible sandy loam type soil.
Spatial and temporal predictions of soil moisture dynamics, runoff, variable source areas and evapotranspiration for plynlimon, mid‐wales
Authors: Quinn P. F. , Beven K. J.
Published: February 2007

For many years hydrologists have tried to build physically realistic models which are still simple enough to be fitted to a range of observations made in the field. This is an ongoing process which will become even more difficult as the quality and variety of field and remotely sensed data improves. Hence models must be able to predict soil moisture patterns in time and in space as well as the outflow hydrograph. The model presented here (TOPMODEL) aims to predict the nature of variable source areas in a way that reflects their dynamics over space and time. All component processes are described and shown in operation. As TOPMODEL and similar models have a growing popularity, this paper can be seen as a demonstration of the model's predictive capabilities. The model is applied to the catchments of Plynlimon, mid‐Wales for 1984, 1985 and 1986 data sets. The model has been thoroughly tested and cross‐validated against independent data sets for different time periods, for a separate catchment, for internal gauges and for wet and dry periods. The resulting predicted soil moisture patterns show a small, semi‐permanent variable source area that has the ability during large storms to expand dynamically over short time periods. Spatial predictions of evapotranspiration are also shown which reflect the influence of soil moisture patterns on this process. The weakest component of the model is the representation of root zone evaporation and how this pre‐sets the antecedent condition of the catchment during long dry periods.
Determination of basin lag time in rainfall‐runoff investigations
Authors: Jin Chang‐Xing
Published: February 2007

Basin lag time varies not only between basins but also within a basin. To explain this variation, the basin lag time was hypothesized as a function of the ratio of the channel length from the centroid to the outlet of the basin, divided by the velocity of flow at the gauging site at the time of passage of peak discharge. The records of six basins were used to test this hypothesis. The results are not incompatible with this hypothesis.
Sampling strategy to describe the temporal hydrochemical characteristics of an alpine proglacial stream
Authors: Gurnell A. M. , Brown G. H. , Tranter M.
Published: February 2007

A hierarchical sampling programme (including continuous monitoring, twice‐daily sampling and sampling at hourly intervals over selected 24 hour periods) was devised to support hydrochemical and hydrological research programmes on an alpine proglacial stream. The rationale for the research and for the sampling programme are explained and the hydrochemical time series generated over an ablation season are analysed to assess the degree to which they support the study aims. It appears that there is no satisfactory substitute for the chemical analysis of at least two water samples taken at approximately maximum and minimum discharge every day, if seasonal variations in meltwater chemistry are to be effectively characterized. Such time series data can be used to estimate Box‐Jenkins transfer function‐noise models between particular solutes (SO2−4, Ca2+, Mg2+, Na+ and possibly K+) and either discharge or electrical conductivity, which can then be used to fill any short gaps in the data. This approach is not satisfactory even for filling short gaps in the twice‐daily determinations of pH, HCO−3 and NO−3. At the diurnal time‐scale (based on hourly determinations over 24 hour periods) electrical conductivity seems to provide a good surrogate for most of the solutes studied. HCO−3, SO2−4, Ca2+ and Mg2+ were found to be particularly strongly related to electrical conductivity and there was little if any significant serial autocorrelation in the residuals from all of the simple linear regression relationships that were estimated between individual species and conductivity. It is concluded that the hierarchical sampling design was suitable for the purposes of the study, and that the continuous monitoring of electrical conductivity provides excellent supporting information to the chemical analysis of water samples if it is used carefully as a means of short term calibration and interpolation of the solute record.
In‐channel surficial fine‐grained sediment laminae. Part II: Chemical characteristics and implications for contaminant transport in fluvial systems
Authors: Stone M. , Droppo I. G.
Published: February 2007

Samples of surficial fine‐grained laminae (SFGL) were collected in three south‐western Ontario rivers. Each sediment sample was subjected to a sequential extraction procedure designed to partition particulate metals (Cd, Pb, Cu, Zn) into five operationally defined fractions: (1) exchangeable; (2) bound to carbonates; (3) bound to Fe‐Mn oxides; (4) bound to organic matter; and (5) residual. Particulate phosphus was sequentially extracted from the sediment samples into three fractions: (1) non‐apatite inorganic P; (2) apatite P; and (3) organic P.

The major accumulate phases of trace metals in SFGL are carbonates, Fe‐Mn oxides and organic matter. The content of NAIP in SFGL ranged from 17 to 38% of total particulate P. Compared with suspended and bed sediments, levels of P and trace metals in SFGL were lower at the study sites. A conceptual overview of physical, chemical and biological processes influencing formation of SFGL and the potential role of this fine‐grained sediment for contaminant transport in fluvial systems is presented.
Invariance and scaling properties in the distributions of contributing area and energy in drainage basins
Authors: La Barbera P. , Roth G.
Published: February 2007

The cumulative probability distributions for stream order, stream length, contributing area, and energy dissipation per unit length of channel are derived, for an ordered drainage system, from Horton's laws of network composition. It is shown how these distributions can be related to the fractal nature of single rivers and river networks. Finally, it is shown that the structure proposed here for these probability distributions is able to fit the observed frequency distributions, and their deviations from straight lines in a log‐log plot.
Flow transmission along an arid zone anastomosing river, cooper creek, australia
Authors: Knighton A. David , Nanson Gerald C.
Published: February 2007

Cooper Creek is characterized by an exceptionally wide floodplain and a complex system of anastomosing channels which together can accommodate a large range of highly variable flows. In consequence flood frequency curves are unusually steep. With minimal tributary contribution over the two study lengths — Currareva‐Nappa Merrie (> 400 km) and Nappa Merrie‐Innamincka (32 km) — downstream output is largely controlled by upstream input, so that similar flow regimes and hydrograph forms can be maintained despite transmission losses and the variable activation of channels.

Input‐output relationships defined in terms of total flow volume and peak discharge suggest that, above a threshold flow of about 25% duration, transmission losses exceed 75% on average over the Currareva‐Nappa Merrie length. The large difference in absorption between primary channels on the one hand and subsidiary channels and the floodplain surface on the other means that transmission losses vary non‐linearly with stage. They are relatively low when flow is confined to the primary channels, but increase at higher stages as lesser channels and the floodplain are activated. Early levels do not recur until flows of < 0.5% duration are attained when output/input ratios increase rapidly with discharge. The influences of seasonality and background flow on output discharge are small relative to that of input discharge.

Despite the long river distance, peak flows at Currareva and Nappa Merrie are well correlated. However, over the shorter Nappa Merrie‐Innamincka length with its more confined system of channels, correlations are better and transmission losses less. They vary from 60% just above the threshold discharge to <10% at flows below 20% duration. Over this length outflow hydrographs can be effectively estimated by the three parameter Muskingum procedure, at least on an event by event basis, but further application must await additional records to understand fully how the parameters vary in an environment where streamflow is transmitted through a highly variable system of channels.
Testing and comparison of four ionic tracers to measure stream flow loss by multiple tracer injection
Authors: Zellweger Gary W.
Published: February 2007

The ionic tracers lithium, sodium, chloride and bromide were used to measure flow loss in a small stream (≈︁ 10 ls−1). An injectate containing all four tracers was added continuously at five sites along a 507 m study reach of St Kevin Gulch, Lake County, Colorado to determine which sections of the stream were losing water to the stream bed and to ascertain how well the four tracers performed. The acidity of the stream (pH 3.6) made it possible for lithium and sodium, which are normally adsorbed by ion exchange with stream bed sediment, to be used as conservative tracers. Net flow losses as low as 0.8 ls−1, or 8% of flow, were calculated between measuring sites. By comparing the results of simultaneous injection it was determined whether subsections of the study reach were influent or effluent. Evaluation of tracer concentrations along 116 m of stream indicated that all four tracers behaved conservatively. Discharges measured by Parshall flumes were 4–18% greater than discharges measured by tracer dilution.
Sources and sinks of sea salt in a newfoundland blanket bog
Authors: Price Jonathan S.
Published: February 2007

Over an oceanic peatland, the concentration of Na in fog averaged 38.1 mgl−1 compared with 1.8 mgl−1 in rain, resulting in a significant flux of mineral elements to the surface. Between 16 May and 20 June 1990 the average mass flux of Na to the bog surface by fog, rain, and dry deposition was 21.9, 10.4 and 7.0 mg m−2 d−1. There was little long‐term storage of Na within the peatland system, where Na losses measured in stream runoff averaged 34.8 mg m2 d−1, and deep groundwater losses 4 mg m−2 d−1. Calcium and Mg were preferentially retained in the organic soil, whereas K was relatively mobile. Potassium tended to become concentrated in the unsaturated zone. Stream runoff had a consistently higher pH than groundwater, corresponding to higher Ca and Mg concentrations, which may have been from mineral sources in the headwater ponds. Otherwise, the stream water chemistry was closely related to groundwater in the upper layers of the peat deposit.
Converting tropical rain forest to forest plantation in sabah, malaysia. Part I. Dynamics and net losses of nutrients in control catchment streams
Authors: Grip H. , Malmer A. , Wong F. K.
Published: February 2007

Streamwatcr chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, including controls in rain forest and secondary vegetation after the [Borneo fire] of 1982–3 and comparing the effects of different ways of establishing forest plantations with Acacia mangium. Three catchments were covered with selectively logged lowland hill dipterocarp forest (W4‐W6) and three (W1‐W3) with secondary vegetation after forest fires. The control catchments, W3 and W6 reported in this paper, had no treatments applied. Reference monitoring at all streams was for 25 months and the total period of study reported here is 64 months. The soils in the catchments were mainly Orthic Acrisol in W3 and Gleyic Podsol in W6 and a mix of both soil types in the other catchments.

Element baseflow concentrations were generally low and not significantly different from stormflow concentrations for all streams during the reference period. Concentrations were also generally consistently low for the two control streams during the whole period of measurement. Chemical inputs as wet deposition were low as a result of a high input from local convection.

The rain forest on the Podsol had a tight nutrient circulation indicated by small net losses of macronutrients. The Podsol was found to have poorer conditions for soil mineralization and more surficial runoff, resulting in higher loads of S, C and N in the organic phases, with higher organic C/N ratio, in the discharge. Nitrogen was found to accumulate in both catchments. An almost double accumulation of N in W3 was attributed to a larger biomass accumulation continuing after the forest fire 3–8 years earlier. On the other hand, the Acrisol in W3 had much larger net losses of S, Si, K, Ca, Mg and Na. Most of differences could be attributed to differences in weathering between the soils and local mineralogical differences.
Hydrological management of a cutover peatland
Authors: Heathwaite A. L.
Published: February 2007

Mechanisms for preserving the hydrological balance of Thorne Moors National Nature Reserve (NNR) while allowing peat extraction to continue in the surrounding peatland are examined. Three strategies exist for modifying seepage losses from the NNR: (I) re‐direction of pump drainage waters from the peat extraction areas; (II) provision of a hydrological buffer zone around the NNR; and (III) mechanical compaction of the boundaries of the buffer zone. Strategy II (increased width of the buffer zone) should be used together with strategy III (compaction) for the maximum reduction of seepage losses from the NNR. If strategy I (water level manipulation) is also adopted, it may be possible to reduce the width of the hydrological buffer zone around the NNR.
Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 2. The native forest water balance and changes in streamflow after harvesting
Authors: Rowe L. K. , Pearce A. J.
Published: February 2007

Six small, steep, south‐west facing catchments (1.63–4.62 ha) have been monitored in Westland, New Zealand since 1974. Two catchments were retained in native mixed evergreen forest and the rest were subjected to various harvesting and land preparation techniques before being planted with Pinus radiata between 1977 and 1980.

The 11‐year water balance for the native forest catchments was: rain = streamflow + interception loss + transpiration + seepage (2370mm = 1290mm + 620mm + 360mm + 100mm). In the year after treatment streamflow generally increased by 200–250 mm, except for one treatment (clearfelling, herbicide application, no riparian reserve) where the increase was 550 mm. The catchments were planted with Pinus radiata, but rapid colonization by bracken (Pteridium esculentum) and Himalayan honeysuckle (Leycesteria formosa) led to a rapid decline in streamflow, which returned to pre‐treatment levels after an average of about five years. Streamflow yields then continued to decline for another two to three years before stabilizing at a level about 250mm yr−1 lower than pre‐treatment levels. At this time the catchments had a dense bracken/honeysuckle understorey beneath 5 m tall pine trees.
Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 3. Stream temperatures
Authors: Rowe L. K. , Taylor C. H.
Published: February 2007

Eight small steep south‐west facing catchments (1‐63‐8‐26 ha) have been monitored in Westland, New Zealand since 1974. Two catchments were retained in native mixed evergreen forest and the rest were subjected to various harvesting and land preparation techniques before being planted with Pinus radiata between 1977 and 1980. Stream temperatures were measured in all catchments for 11 years, including up to four years before harvesting.

The streamwater temperature regime under the native forest cover has a seasonal cycle, with an annual mean of about 9°C and mean daily temperatures ranging between a winter minimum of about 5.8°C and a summer maximum of 12.S°C. After harvesting, the winter minimum stream temperatures in all trials were unchanged as topography exerts the major control over incoming solar radiation. The largest rises in mean summer stream temperatures, up to 5.5°C, were in the catchments that had been clearcut and burnt before planting. The maximum stream temperature recorded was 22.8°C in a clearcut catchment with no riparian reserve. Summer stream temperatures in this catchment were up to 11°C higher than in an adjacent control catchment. Summer stream temperature rises in catchments with riparian reserves were less than 1.5°C.

Seven years after harvesting, stream temperatures were dropping towards pre‐treatments levels in only two of the six treated catchments as revegetation of the riparian areas occurred and the plantations became established.

As these small headwater streams discharge into streams with flows one or two orders of magnitude larger, the increases in summer stream temperatures will be rapidly dissipated. However, the cumulative impact of harvesting many small headwater catchments that discharge into a larger stream could have a noticeable effect on stream temperature if intact riparian reserves were not retained in both headwater and main streams.
Accuracy of kinematic wave and diffusion wave approximations for space‐independent flows with lateral inflow neglected in the momentum equation
Authors: Singh V. P.
Published: February 2007

Error equations for the kinematic wave and diffusion wave approximations with lateral inflow neglected in the momentum equation are derived under simplified conditions for space‐independent flows. These equations specify error as a function of time in the flow hydrograph. The kinematic wave, diffusion wave and dynamic wave solutions are 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; and it reflects the effect of bed slope, channel roughness and acceleration due to gravity when the initial condition is vanishing. The error equations are found to be the Riccati equation. The structure of the error equations in the case when the momentum equation neglects lateral inflow is different from that when the lateral inflow is included.
Multiple flow direction algorithms for runoff modelling in grid based elevation models: An empirical evaluation
Authors: Holmgren Peter
Published: February 2007

When pathways for groundwater flow are defined in grid based elevation models, the grid structure creates some obstacles as it only allows for eight flow directions. Earlier algorithms have used arbitrarily designed flow distributions, which have resulted in either too diverging or too converging flow patterns. This study defines a computationally simple distribution function, where the converging nature (x) can be altered. A material of reference flow distributions was produced through simulation in four elevation models. The distribution function was tested for different values on x, against the reference. The results show a stable correlation pattern between the tested function and the reference. Optimum values on x were found, which suggest that the flow distribution from a grid cell should be weighted with the slope gradient raised to the power of 4–6.