bluuebunny/crossref_metadata_2025 huggingface dataset:
Pollution Loads Discharged from Combined Sewer Overflows: Theoretical Approach and Long Term Numerical Assessment
Authors: Mignosa Paolo , Paoletti Alessandro
Published: May 2018

The paper describes a theoretical analysis and a numerical assessment of pollutant loads discharged from Combined Sewer Overflows (CSOs) - with or without stormwater tanks – into the environment.

The theoretical approach was based on certain simple assumptions, reasonably valid if the time scale of the problem involved is long enough (month/ year), in that single-event simulation is not interesting at all. Two main parameters related to the rainfall regime were found to be significant: the total volume of water discharged from the structure and the effective mixing factor between sanitary sewage and storm runoff.

A numerical assessment of these two parameters was then made, on an annual basis, by means of a long-term rainfall series recorded in Milan, Italy.

Both the “simple” CSO structure and the CSO coupled with stormwater tanks (on-line or off-line) were considered. The resulting graphs make it possible to evaluate the total annual load discharged from CSOs into the environment and the potential reduction obtained by adding a storage capacity to the overflow.

This estimation could be of interest for persistent pollutants (phosphorus, heavy metals) discharged into low-recirculation bodies (lakes, estuaries, lagoons, closed seas).
The Importance of Rainfall Distribution in Urban Drainage Operation
Authors: Nelen Fons , Mooijman Annemarieke , Jacobsen Per
Published: May 2018

A control simulation model, called LOCUS, is used to investigate the effects of spatially distributed rain and the possibilities to benefit from this phenomenon by means of real time control. The study is undertaken for a catchment in Copenhagen, where rainfall is measured with a network of 8 rain gauges. Simulation of a single rain event, which is assumed to be homogeneous, i.e. using one rain gauge for the whole catchment, leads to large over- and underestimates of the systems output variables. Therefore, when analyzing a single event the highest possible degree of rainfall information may be desired. Time-series simulations are performed for both an uncontrolled and a controlled system. It is shown that from a statistical point of view, rainfall distribution is NOT significant concerning the probability of occurrence of an overflow. The main contributing factor to the potential of real time control, concerning minimizing overflows, is to be found in the system itself, i.e. the distribution of available storage and discharge capacity. When other operational objectives are involved, e.g., to minimize peak flows to the treatment plant, rainfall distribution may be an important factor.
Evaluating the Effectiveness of a Mine Tailing Cover
Authors: Herbert Roger B.
Published: May 2018

This study presents a method for evaluating the effectiveness of a mine tailing cover. The cover is designed with a 0.5 m layer of clay covered by a 1.5 m layer of glacial till; full water saturation of the clay layer is assumed to be necessary for the maximal reduction of oxygen transport through the cover. The evaluation of cover effectiveness is based on: 1) the reduction of leachate production, and 2) the ability of the clay layer to remain water saturated and avoid cracking. Using 1990 precipitation data, the numerical model SUTRA simulates unsaturated flow in the cover, with results interpreted in terms of pressure head variations and vertical discharge from the cover. The modeling results indicate that this cover design would adequately reduce leachate production from a tailing deposit. In addition, the water saturation of the clay layer remains above its plastic limit during a simulated year of normal recharge conditions; it is therefore not likely that the clay layer would crack. A sensitivity analysis with different hydraulic parameter values is performed, and shows that leachate production is most sensitive to clay hydraulic conductivity, while the water saturation of the clay layer is sensitive to both clay hydraulic conductivity and till porosity.
Subsurface Flow in a Shallow Soil Canadian Shield Watershed
Authors: Renzetti Adrian V. E. , Taylor Colin H. , Buttle James M.
Published: May 2018

Past studies in Canadian Shield headwater catchments have identified the importance of subsurface flow mechanisms in generating storm runoff. Recent work in the Muskoka-Haliburton region of south-central Ontario has suggested that subsurface flow within hillslopes with shallow soils occurs primarily along impermeable bedrock surfaces. Two trenches were dug on the side slope of a small headwater catchment and instrumented to measure flows at different levels in the soil. Results show that flow over the bedrock surface constitutes the largest component of hillslope discharge during fall rain storms. Peak discharge and recession rates for bedrock surface flow hydrographs were synchronous with channel discharge. Calculations show that this component of hillslope flow could account for the majority of peak discharge during storm events.
Modelling the Hydrological Response of Extreme Floods in Sweden
Authors: Harlin Joakim
Published: May 2018

Hydrological models are today used for simulating extreme floods with the purpose of designing dams and spillways. In doing so, an extrapolation beyond the floods of the calibration period is made. This paper addresses this problem in connection to the HBV hydrological model. The model component describing flood dynamics, the runoff-response function, is studied. The methodology has been to calibrate different runoff-response functions over small to moderately large floods and to verify the performance over independent periods containing large experienced floods. Furthermore, the different model versions were run with extreme rainfall in order to generate design floods. It was found that the five-parameter response function of the original HBV model could be replaced by nonlinear functions including fewer parameters. However, it was difficult to select any response function formulation as significantly better than the others when extreme floods larger than those of the calibration period were simulated.
Tracer Test in Fractured Chalk
Authors: Brettmann K.L. , Jensen K. Høgh , Jakobsen R.
Published: May 2018

A two-well tracer test carried out in fractured chalk was analyzed using a three-dimensional finite-difference model for flow and transport which, was constructed on the basis of the geological and hydraulic information collected at the field site. The model was developed as a dual-porosity continuum model, in which advection was assumed to occur only in the fractures, and the water in the porous matrix was assumed to be static. The exchange of solute between the fractures (mobile phase) and the porous matrix (immobile phase) was assumed to occur as a diffusion process in response to the local concentration difference of solute between the two phases. Simulations from the dual-porosity model reproduced the shape of the observed breakthrough curves, although some portions of the tail were not accurately represented. The model was also applied as a single-porosity model for advection and dispersion in the fractures with no solute exchange with the porous matrix. The simulations from the single-porosity model greatly overestimated the observed lithium concentrations, and showed very little tailing effect in the falling limb. The study shows that, based on the given tracer test, solute transport in a fractured chalk cannot be represented by a single-porosity approach and hence when dealing with contaminant transport in such systems, both a fractured and a porous domain need to be considered.
Snowmelt Runoff and Total Solids Production in a Discontinuous Permafrost Basin
Authors: Chacho Edw. F.
Published: May 2018

Snowmelt runoff and total suspended solids were measured for two years on Glenn Creek, a small, second-order, subarctic stream located near Fairbanks, Alaska, within the Yukon-Tanana Uplands physiographic province. The stream drains a 2.25-km2 research watershed of which 70 % is underlain by permafrost. The two years of study represent very different snowmelt hydrographs due to differences in the snowpacks. In 1985, the snowpack was 180 % of the long-term average, while in 1988 it was only 56 % of the average. During both years, 60 % of the total snowmelt-season water yield had passed before a significant rate of solids yield was observed. Also in both years the peak in total suspended solids concentration lagged the stream discharge peak by three days. Diurnal fluctuations in discharge and total suspended solids concentrations are well-defined, including a peculiar occurrence of double diurnal peaks in the discharge hydrograph during portions of the snowmelt season. The diurnal fluctuations in solids concentration are shown to be consistent with water temperature fluctuations. In 1988, the percentage of organics in the total suspended solids was scattered from 0 % to 66 % during the snowmelt season.
Numerical Modelling of Phase Change in Freezing and Thawing Unsaturated Soil
Authors: Engelmark H. , Svensson U.
Published: May 2018

This paper presents a new method for handling the phase change process in numerical simultations of freezing and thawing soils. Moisture and heat transfer in soils subjected to both freezing and thawing are discussed. Simulated freezing results of temperature and total water content (water + ice) are compared with experimental data reported by Jame (1977). Simulated and experimental results were similar. The effects of different time-dependent temperature boundary conditions were evaluated and discussed. The method was used both with abrupt and smooth temperature boundary conditions and both resulted in stable numerical solutions. Finally, results from a simulation of a freezing and thawing cycle are presented and discussed qualitatively.
Temporal Variation in Snowcover Area During Melt in Prairie and Alpine Environments
Authors: Shook K. , Gray D.M. , Pomeroy J.W.
Published: May 2018

Information on the temporal variation in snow-covered area of watershed during melt is requisite for accurate predictions of runoff. The amount of the gross watershed area that is snow-covered affects runoff primarily in two ways: a) it influences the melt rate, because patches of bare ground affect the energy balance of the snow field, and b) it governs the contributing area of runoff.

This paper examines the area-frequency and perimeter-area characteristics of soil and snow patches that form during ablation of seasonal snowcovers in Prairie and Alpine environments. It uses fractal geometry as a basis for quantifying these properties.

Image analyses are applied to aerial photographs taken during snowmelt on two small watersheds: one in the West-central part of the Province of Saskatchewan in the Canadian Prairies, the other in the alpine region of the Austrian Alps. The results of the study suggest that the soil and melting snow patches behave as fractals, that is their perimeter-area and area-frequency characteristics can be described by simple power equations with patch area. The perimeter-area ratio of the soil and snow patches decreases with increasing size of patch, but at a smaller rate than for Euclidean objects. The area-frequency characteristics of snow patches follow a hyperbolic distribution with relatively few large patches and numerous small patches. It is suggested that the soil and snow patches have the same fractal dimension. It is concluded that snow patches are not random and their size distribution is predictable.

The variation in the edge length of a snow field per unit basin area during ablation is demonstrated. A maximum value of the ratio is reached when a basin has 45-65 % snowcover. With snow coverage in this range the potential for local advection increasing melt under a specific set of climatic conditions is greatest.
Cylindrical Piezometer Responses in a Humified Fen Peat
Authors: Baird Andrew J. , Gaffney Simon W.
Published: May 2018

Most studies of peat hydrology have concentrated on processes below the watertable where pore water pressures and hydraulic conductivity are measured using piezometers. While piezometer head recovery tests in poorly humified bog peats give responses similar to those expected from rigid soils, a number of studies have suggested that matrix compressibility might be important in affecting head recovery test results in well humified bog peats. Until now no data have been available for humified fen peats. We apply the response time theory of Brand and Premchitt (1982) for compressible soils, and Hvorslev (1951) for rigid soils, to head recovery test data obtained from open cylindrical piezometers installed in a humified fen peat in Somerset, England. To the best of our knowledge this is also the first quantitative application of compressible soil theory for piezometers to any peat. Our results show that compression and swelling of the peat matrix do affect the course of head recovery in the piezometers used in the study. We comment on the significance of this finding for the calculation of hydraulic conductivities and pore water pressures in this peat type.
Areal Extent of Seasonal Snow Cover in a Changed Climate
Authors: Rango A. , Martinec J.
Published: May 2018

In mountain snow basins, a change in climate will likely cause a change in the basin snow cover extent. A procedure for evaluating whether a given climate change scenario will speed up or slow down the seasonal decrease of snow covered area is outlined with hypothetical examples for a simple basin. This procedure has two main purposes. First, it can be used to generate snow covered area data in a new climate for input to runoff models such as the Snowmelt-Runoff Model (SRM). Second, it could potentially be used to provide input to climate models that require knowledge of the land area covered by snow at a given time. A computer program is now operational for use on real basins and is demonstrated on the Rio Grande basin in Colorado and the Illecillewaet River basin in British Columbia.
Entering the Era of Distributed Snow Models
Authors: Kirnbauer R. , Blöschl G. , Gutknecht D.
Published: May 2018

Traditionally, snowmelt modelling has been governed by the operational need for runoff forecasts. Parsimony in terms of model complexity and data requirements was a major concern. More recently, the increased importance of analyzing environmental problems and extreme conditions has motivated the development of distributed snow models.

Unfortunately, the use of this type of models is limited by a number of factors including a) the extreme heterogeneity of the hydrologic environment, b) the mismatch of scales between observed variables and model state variables, c) the large number of model parameters, and d) the observability/testability problem.

This paper discusses the implications of these constraints on the use of site and catchment scale concepts, regionalisation techniques, and calibration methods. In particular, the point is made that in many cases model parameters are poorly defined or not unique when being optimized on the basis of runoff data. Snow cover depletion patterns are shown to be vastly superior to runoff data for discriminating between alternative model assumptions. The patterns are capable of addressing individual model components representing snow deposition and albedo while the respective parameters are highly intercorrelated in terms of catchment runoff.

The paper concludes that site scale models of snow cover processes are fairly advanced but much is left to be done at the catchment scale. Specifically, more emphasis needs to be directed towards measuring and representing spatial variability in catchments as well as on spatially distributed model evaluation.
The Role of Turbulent Heat Fluxes in the Energy Balance of High Alpine Snow Cover
Authors: Plüss C. , Mazzoni R.
Published: May 2018

Energy balance measurements over a seasonal snow cover were performed near Davos, Switzerland at 2,540 m a.s.l. The energy fluxes were studied over dry and melting snow covers. The beginning of snowmelt clearly coincides with the beginning of positive daily sums of net radiation. During snowmelt, net radiation is the dominant energy source. Latent and sensible heat fluxes do not show a significant seasonal change and remain slight over most of the measuring period. This minor contribution of the turbulent heat fluxes can be attributed to generally low wind speeds in this inner alpine region and to frequent inversions over the melting snow cover.

In a changing climate the turbulent heat fluxes could become increasingly important in the energy balance. Therefore, evaluations of the turbulent heat fluxes from profile measurements and the eddy correlation method are compared with simple approximations commonly used in snowmelt models. The conditions under which these approximations can be used for routine discharge forecasts are identified.
Long-Term Records of Snow Cover Water Equivalent in the Swiss Alps
Authors: Rohrer M. B. , Braun L. N. , Lang H.
Published: May 2018

The snow-water equivalent (SWE) of the seasonal snow cover is an important component of the water cycle in the Swiss Alps. It is used for predicting seasonal discharge, for short-range discharge forecasts and also for assessing water quality aspects. The SWE has been measured every two weeks at about 50 stations located between 860 and 2,540 m a.s.l. for more than 30 years. In addition there are special investigation areas with stations located between 600 m and 2,900 m a.s.l. where SWE is measured once per winter. The main characteristics of temporal and spatial SWE distributions are analyzed. The variations of SWE values depend in ranking order on elevation, on the year-to-year variations, on the region and on the exposition. The standardized SWE-values depend mostly on the year-to-year variations and on the region.
Integration of Field Data into Operational Snowmelt-Runoff Models
Authors: Brandt M. , Bergström S.
Published: May 2018

Conceptual runoff models have become standard tools for operational hydrological forecasting in Scandinavia. These models are normally based on observations from the national climatological networks, but in mountainous areas the stations are few and sometimes not representative. Due to the great economic importance of good hydrological forecasts for the hydro-power industry attempts have been made to improve the model simulations by support from field observations of the snowpack. The snowpack has been mapped by several methods; airborne gamma-spectrometry, airborne georadars, satellites and by conventional snow courses. The studies cover more than ten years of work in Sweden. The conclusion is that field observations of the snow cover have a potential for improvement of the forecasts of inflow to the reservoirs in the mountainous part of the country, where the climatological data coverages is poor. This is pronounced during years with unusual snow distribution. The potential for model improvement is smaller in the climatologically more homogeneous forested lowlands, where the climatological network is denser. The costs of introduction of airborne observations into the modelling procedure are high and can only be justified in areas of great hydropower potential.
Prediction of Log-Transmissivity
Authors: Christensen Steen
Published: May 2018

Two physically based models are derived that can be used to predict the log-transmissivity from the lithology, e.g. as logged in boreholes. The first model uses the lithology as the only predictor, whereas the second model uses the lithology and the specific capacity as simultaneous predictors. The model parameters can be estimated by statistical methods from actual observations.

The methods are applied to three case studies. A comparison with Christensen (1995) shows that the lithology in some cases is a better single predictor of log-transmissivity than the specific capacty; in other cases the opposite is true. This suggests that the proposed joint model is preferable to either of the single predictor models. In two cases the joint model improves the prediction considerably when compared with the single predictor models; in the third case the joint model is at least as good as the single predictor models.
Comparative Model Estimates of Interception Loss in a Coniferous Forest Stand
Authors: Tallaksen Lena M. , Schunselaar Sandra , van Veen Rob
Published: May 2018

Measurements of throughfall in a coniferous forest stand were analyzed and compared with model estimates of interception loss using three different types of models: the Nordic HBV model, the AMOR model and a simplified Rutter model. Two years of seasonal data were available. The 90% confidence interval on estimated average throughfall over the area decreased with storm size and approached a constant value of 15% for events larger than 10 mm of rainfall. Average interception loss was 27% during both the 1993 and 1994 seasons. The Rutter model performed slightly better than the other two; however, all models failed to reproduce the very high interception losses following some of the largest storms. The AMOR model, which is a modified version of the British MORECS model, also underestimated the loss for small and medium-sized storms, and it is necessary to include a linked storage in the model. The Nordic HBV model proved satisfactory as compared to the other two more data demanding models; it does, however, require calibration. The Rutter model has the largest potential to account for the special meteorological conditions prevailing during periods of high losses.
The Exchange of Water and Salt across the Drogden Sill in Øresund September 1993-November 1994
Authors: Jakobsen FI. , Lintrup M.J.
Published: May 2018

In this paper accurate hourly time series of water and salt transport across the Drogden Sill in Øresund are presented for a period of more than one year. The investigation is based on measured current, salinity and water levels from two fixed stations in the Drogden Channel and the Flinten Channel. The water transport is calculated by the method outlined in Jakobsen and Castejon (1995), which is extended in the present paper to include salt transport. The resulting water and salt transport distributions are given as functions of time or salinity. The data analyses show a net water discharge out of the Baltic Proper across the Drogden Sill of 2.5×103 m3/s and a net salt flux into the Baltic Proper of 58 tonnes/s. The outflow is water with a salinity less than 12 g/kg, while the inflow takes place in the interval from 12 g/kg to 32 g/kg. The Knudsen relations are extended by two equations regarding gross transport, whereby the barotropically pulsating flow of changing salinity may be equated with a corresponding two-layer system of opposing residual fluxes.
The Use of SAR Satellite Imagery to Measure Active Layer Moisture Contents in Arctic Alaska
Authors: Kane D. L. , Hinzman L. D. , Yu Haofang , Goering D. J.
Published: May 2018

Synthetic aperture radar (SAR) has the potential for measuring near surface soil moisture contents for very large areas. The polar orbiting European Remote Sensing satellite (ERS-1) of the European Space Agency (ESA) has onboard an active C-band SAR sensor. We have analyzed SAR imagery over a small research watershed, Imnavait Creek, located in the northern foothills of the Brooks Range in Alaska, U.S.A. This watershed is treeless and completely underlain with permafrost. After geometrically and radiometrically correcting each pixel (25 m by 25 m) in the image, corrected pixel values were correlated with corresponding field moisture contents measured along transects in the watershed for two passes of the satellite. Coefficients of determination, r2, between the corrected pixel value and measured moisture content were 0.49 on June 12, 1993 and 0.53 on August 2, 1993; with the data sets combined the value was 0.50.
A Comprehensive Model for Correcting Point Precipitation
Authors: Allerup P. , Madsen H. , Vejen F.
Published: May 2018

Wind induced errors in precipitation measurements result in systematic deficits, which are particularly large when the precipitation falls as snow combined with high wind speed. The actual magnitude of the deficit can amount to more than half of the true precipitation. In order to correct for these deficits, newly developed statistical models for solid and mixed precipitation are presented; together with a correction model for liquid precipitation presented earlier, a comprehensive system of correction models is now available. Statistical errors on the corrections are estimated.
Comparison of Sediment Rating Curves Developed on Load and on Concentration
Authors: Jansson Margareta B.
Published: May 2018

A sediment rating curve developed as a linear regression on logged values which is back-transformed must be corrected for the bias introduced by the log transformation. This article shows that the variances are identical for linear regressions based on values of logged load and logged concentration from the same data set. This means that the bias correction factoss 101.1513σ2 for the back-transformed regressions are equivalent. Therefore a back-tranoformed log regression based on loads corrected for bias gives identical sedimett discharges to a back-transformed log regression on concentrations corrected for bias. Regression equations from gauging stations in two neighbouring basins in Costa Rica confirm this conclusion.

Mean loads for individual discharge classes were plotted on diagrams in log scales to find the points where the sedimett rating curve changes direction. When sediment rating curves were developed on logged mean concentrations, water discharge weighted mean concentrations had to be determined in order to produce equations comparable to those on logged mean loads. Consequently, discharge weighted mean concentrations must be used in a plot to determine the change in direction of a sedimett rating curve and to check the goodnsss of fit of a regression developed by any model employing concentration as the dependent variabe.
Observations of the Specific Resistance in the Øresund
Authors: Jakobsen FI. , Lintrup M. J. , Møller J. Steen
Published: May 2018

The specific resistance and three other secondary coefficients in the instantaneous integral energy equation describing the flow in the Øresund strait, are accurately estimated from over two years of high resolution measurements. Parameter variation due to stratification, effectively insulating the flow from the effect of bottom friction, is demonstrated and quantified. Also, parameter variation with the flow direction is quantified. Residual error dynamics is discussed and described. The relevance of an additional linear resistance term in the flow energy equation is discussed.
Using the Rational Method for Design in Complex Urban Basins
Authors: Bengtsson Lars , Niemczynowicz Janusz
Published: May 2018

Because of its simplicity the rational method is still frequently used in urban planning and design. In this paper using the time-area method and statistically derived design storms, the design peak flow is computed for urban basins of different complexity and compared with the design flow determined from the rational method. It is shown that the design flow is underestimated using the rational method unless a reduced time of concentration is used. The relation between travel times in different parts of a drainage system is used to correct the design flow computed by the traditional rational method.
Animal Communities in Icelandic Rivers in Relation to Catchment Characteristics and Water Chemistry
Authors: Gíslason Gísli Már , Ólafsson Jón S. , Adalsteinsson Hákon
Published: May 2018

Catchment areas of Icelandic rivers are mostly barren or with little vegetation cover in the highlands, but with heathland and mire vegetation in the lowlands. Chemical composition and nutrient availability in Icelandic rivers are influenced by geology, topography and vegetation cover in the river basins. This seems to determine the density and diversity of benthic invertebrates, species composition of anadromous fish and catch of salmon in Icelandic rivers. Species composition of benthic communities is determined by particulate organic matter drifting downstream from river head-waters. Filter feeding blackfly larvae dominate lake outlets, while algal grazing chironomid larvae dominate rivers not influenced by lakes. In well vegetated catchment basins, lake-fed rivers have higher catches of salmon than non-lake fed rivers. Only a few of the rivers flowing from poorly vegetated areas sustain salmon. Glacial rivers have the lowest density and diversity of benthic invertebrates of all river groups and do not sustain fish populations.
Concentration Data and Dimensionality in Groundwater Models: Evaluation Using Inverse Modelling
Authors: Barlebo Heidi Christiansen , Hill Mary C. , Rosbjerg Dan , Jensen Karsten Høgh
Published: May 2018

A three-dimensional inverse groundwater flow and transport model that fits hydraulic-head and concentration data simultaneously using nonlinear regression is presented and applied to a layered sand and silt groundwater system beneath the Grindsted Landfill in Denmark. The aquifer is composed of rather homogeneous hydrogeologic layers. Two issues common to groundwater flow and transport modelling are investigated: 1) The accuracy of simulated concentrations in the case of calibration with head data alone; and 2) The advantages and disadvantages of using a two-dimensional cross-sectional model instead of a three-dimensional model to simulate contaminant transport when the source is at the land surface Results show that using only hydraulic heads in the nonlinear regression produces a simulated plume that is profoundly different from what is obtained in a calibration using both hydraulic-head and concentration data. The present study provides a well-documented example of the differences that can occur. Representing the system as a two-dimensional cross-section obviously omits some of the system dynamics. It was, however, possible to obtain a simulated plume cross-section that matched the actual plume cross-section well. The two-dimensional model execution times were about a seventh of those for the three-dimensional model, but some difficulties were encountered in representing the spatially variable source concentrations and less precise simulated concentrations were calculated by the two-dimensional model compared to the three-dimensional model. Summed up, the present study indicates that three-dimensional modelling using both hydraulic heads and concentrations in the calibration should be preferred in the considered type of transport studies.
Observations of Ice and Its Sediments on the Baltic Sea Coast
Authors: Leppäranta Matti , Tikkanen Matti , Shemeikka Petri
Published: May 2018

Ice samples were taken in winter 1996 for determining the quality and quantity of sediment inclusions (suspended matter). The study area was the coast of the Gulf of Finland in the Baltic Sea. The data are from 13 sites and include for the water fraction of a melted ice sample pH, electric conductivity and soluble matter, and for the suspended matter within the ice include the total mass, organic proportion and concentrations of some chemical elements. Three lakes were sampled for regional freshwater references. The soluble matter was mainly due to the salts in sea water and amounted to around 1 g/l (25-50% of the water salinity), and the pH was 4.0-7.5. The sediment content was mostly 1-10 mg/l; larger values resulted from industrial and traffic fallout on ice and snow and from sea bottom sand. Of toxic metals, lead and zinc showed enriched concentrations in ice and snow. The snow cover was also investigated and the result was close to those of the ice samples, but the pH and amount of soluble matter was lower in the snow. A potential ecological risk exists in spring as the ice and snow meltwater, with possibly a very low pH and enriched in pollutants, is mixed with the surface water layer. This layer is particularly thin beneath the fast ice zone.
Modelling Snowmelt Induced Waste Water Inflows
Authors: Semádeni-Davies Annette
Published: May 2018

Impacts of urbanisation on hydrological processes are different for snowmelt and rainfall events. Furthermore, snowmelt and runoff generation differ between rural and urban areas. Within an urban area, melt intensities are increased at some sites; hence, the volume of water early in thaw can be greater than in rural areas. However, shading can reduce melt in other areas so that the melt period is extended. Many surfaces are at least seasonally impervious and generate overland flow - there is an apparent increase in the area contributing to quickflow as normally permeable surfaces become saturated or frozen or both. Water infiltrating permeable soil causes saturation and groundwater recharge so that water can seep into sewers. Regardless of whether water enters via inlets or sewer infiltration, drainage networks ensure swift delivery of melt water to outlets.

Snowmelt induced runoff reaching the Uddebo Waste Water Treatment Plant in Luleå, Sweden, is investigated and a model of urban snowmelt and meltwater routing is proposed. The role of surface type (permeable and impervious) and snow cover characteristics (snow-free, undisturbed, compacted and piled) upon model output is studied. Results are encouraging and provide a good platform for further research.
Estimation of Parameter Uncertainty in the HBV Model
Authors: Seibert Jan
Published: May 2018

Usually the HBV model is calibrated by seeking one optimal parameter set that represents the catchment. From experience we know, however, that it is hardly possible to find an unique parameter set. This is because of errors in both the model structure and the observed variables and because of interactions between the different model parameters. Therefore, there may be many sets of parameters which give similar good results during a calibration period, but their predictions may differ when simulating runoff in the future. In this study a Monte Carlo procedure was used to assess the uncertainty of the parameter estimation and to describe differences in this uncertainty for the various parameters. A fuzzy measure of model goodness was introduced to allow combination of different objective functions. Only a few of the parameters were well-defined, whereas for most parameters good results could be obtained over large ranges. Tentatively an indication of the uncertainty in model predictions arising from the uncertainty in the parameterization was given by viewing the predictions of runoff during two periods.
Geostatistic Interpolation of Soil Moisture
Authors: Kitterød Nils-Otto , Langsholt E. , Wong W. K. , Gottschalk L.
Published: May 2018

The spatial distribution of soil moisture defines preferential flow paths in the unsaturated zone. Hence, three dimensional (3D) estimates of soil moisture are of great importance to understand transport of contaminants as well as remediation processes in the unsaturated zone. In this study 3D estimates conditioned on spatially frequent observations of soil moisture, have been obtained by kriging. The observations were divided into subdomains consistent with the local stratigraphy and directional semivariogram analysis was applied. It was found difficult to clearly identify a 3D semivariogram function in this case, but from a georadar survey two semivariogram functions were derived, describing two different sedimentological units. By conditioning the estimates of soil moisture on the sedimentological architecture computed by indicator kriging, more accurate estimates were achieved. These improvements were quantified by a ‘jackknife’ cross validation procedure. Besides the practical aspects of finding the most important flow paths estimates of soil moisture are valuable when validating unsaturated flow models.
Runoff Processes on a Forested Slope on the Canadian Shield
Authors: Buttle J. M. , Turcotte D. S.
Published: May 2018

Throughfall reaching the ground surface on forested slopes may follow a variety of pathways to receiving water bodies, and travel times and chemical interactions between water and soil may differ between these pathways. We examine the controls that throughfall and pre-event soil water characteristics impose on: 1) separation of incident throughfall between flow over/through the soil's organic mat and subsurface flow; and 2) separation of subsurface runoff between bypassing flow via macropores and translatory flow through the soil matrix. Runoff response to summer and fall rainstorms in 1997 was examined for a forested slope in south central Ontario. Flow over and through the thin podzol soil cover was measured at a throughflow trench, while vertical profiles of soil water content were measured at various sites on the slope. Overland flow increased with throughfall intensity and decreased with antecedent soil wetness, implying that this pathway was most effective during drought conditions which promoted hydrophobicity of the organic layer. Vertical bypassing flow was directly related to throughfall intensity, but independent of pre-event soil water content on the slope. Subsurface runoff properties were also not related to antecedent soil wetness; however, strong association between throughfall intensity and slope runoff suggested that coupled vertical and lateral macropore flow controlled runoff generation during small-to-medium size events. Translatory flow displacement of pre-event soil water on the slope may increase in importance for larger events and greater antecedent wetness conditions than were observed in this study.
Application of a Global Discharge Model to Atmospheric Model Simulations in the BALTEX Region
Authors: Hagemann Stefan , Dümenil Lydia
Published: May 2018

In this study, a hydrological discharge model is presented which may be applied as a tool to validate the simulation of the hydrologic cycle of atmospheric models that are used in climate change studies. It can also be applied in studies of global climate change to investigate how changes in climate may affect the discharge of large rivers.

The model was developed for the application with the climate models used at the Max-Planck-Institute for Meteorology. It describes the translation and retention of the lateral waterflows on the global scale as a function of the spatially distributed land surface characteristics which are globally available. Here, global scale refers to the resolution of 0.5° and lower, corresponding to a typical average gridbox area of about 2,500 km2. The hydrological discharge model separates between the flow processes of overland flow, baseflow and riverflow. The model parameters are mainly functions of the gridbox characteristics of topography and gridbox length.

The hydrological discharge model is applied to the BALTEX (Baltic Sea Experiment) region using input from an atmospheric general circulation model (ECHAM4) as well as from a regional climate model (REMO). The simulated inflows into the Baltic Sea and its sub-catchments are compared to observed and naturalized discharges. The results of this comparison are discussed and the simulated values of precipitation, surface air temperature and accumulated snowpack are compared to both observed data and surrogate data.
Fractures and Biopores in Weichselian Clayey Till Aquitards at Flakkebjerg, Denmark
Authors: Klint Knud Erik S. , Gravesen Peter
Published: May 2018

The distribution of fractures and biopores in a clayey and sandy till aquitard was investigated in two excavations, on southern Zealand, Denmark. A large number of fracture data were measured and quantitative fracture properties calculated. The formation of fractures can be related to the depositional history of the tills during two glacier-advances/retreats and subsequent climatic changes during the Quaternary. The fractures including faults are separated into four systems: 1) Large vertical/subvertical fractures related to the oldest glacier-advance or interstadial climatic influence. 2) Horizontal -subhorizontal fractures related to subglacial drag/shear during a glacial advance from northeast and in an initial stage of a younger glacier-advance from southeast. 3) Normal faults related to subglacial loading during a late stage of the youngest glacier-advance and, 4) Minor desiccation and freeze-thaw fractures related to post-glacial climatic influence. A conceptual macropore distribution model was developed that consists of three zones with different macropore characteristics.
Spatial Variability of Contaminant Transport in a Fractured Till, Avedøre Denmark
Authors: McKay Larry , Fredericia Johnny , Lenczewski Melissa , Morthorst Jørn , Klint Knud Erik S.
Published: May 2018

A field experiment shows that rapid downward migration of solutes and microorganisms can occur in a fractured till. A solute tracer, chloride, and a bacteriophage tracer, PRD-1, were added to groundwater and allowed to infiltrate downwards over a 4 × 4 m area. Chloride was detected in horizontal filters at 2.0 m depth within 3-40 days of the start of the tracer test, and PRD-1 was detected in the same filters within 0.27 - 27 days. At 2.8 m depth chloride appeared in all the filters, but PRD-1 appeared in only about one-third of the filters. At 4.0 m depth chloride appeared in about one-third of the filters and trace amounts of PRD-1 were detected in only 2 of the 36 filters. Transport rates and peak tracer concentrations decreased with depth, but at each depth there was a high degree of variability. The transport data is generally consistent with expectations based on hydraulic conductivity measurements and on the observed density of fractures and biopores, both of which decrease with depth. Transport of chloride was apparently retarded by diffusion into the fine-grained matrix between fractures, but the rapid transport of PRD-1, with little dispersion, indicates that it was transported mainly through the fractures.
Leaching of Phosphate in Structured Soil – a Two Step Process
Authors: Jensen Marina Bergen , Bruun Hansen Hans Chr. , Jørgensen Peter R. , Magid Jakob
Published: May 2018

This paper summarizes a series of experiments on P-leaching in structured clayey soil, mostly conducted on intact soil columns with diameter 0.5 m, and length 0.5, 0.73 or 1.0 m. Breakthrough curves of pulse-applied 32P-. and 3H2O-tracers demonstrated that preferential flow was the dominant process controlling solute leaching. In the upper 0.5 m of the soil profile, dye tracing revealed the active preferential pathways to consist mainly of tubular biopores, while at increasing depths fracture planes became increasingly important. Tracing of surface applied phosphate by use of 32P-autoradiography pointed to larger diameter biopores (diam. > 3 mm) as sole contributors to long-distance phosphate transport. The impacts of ionic strength, reducing soil conditions, faeces application, and soil depth, on P-leaching were investigated, as were the P-sorption characteristics of different macropore wall materials and bulk top- and subsoil. The results suggested P leaching to proceed through two continuously repeated steps: A loading step in which P is loaded from its solid phase sources into mobile solution, and a translocation step in which P is translocated through the soil profile with the mobile solution. Both steps depend on a range of parameters, and P-leaching will occur only if both steps are completed successfully.
Response Time of Forested Mountainous Watersheds in Humid Regions
Authors: Loukas A. , Dalezios N. R.
Published: May 2018

This study proposes an analytical method for the estimation of time lag for forested mountainous watersheds. The water flow in a watershed is separated and analyzed in two phases, the land or hillslope phase and the stream channel phase. In many areas around the globe the flow in a forested high gradient watershed is generated through subsurface pathways as several field experiments have shown. The kinematic wave theory is used to describe the generation of flow from steep forested hillslopes. This hillslope runoff is, then, used as input to the stream channels. The equations were developed by assuming kinematic conditions in the stream channel and that the stream slope and the roughness coefficient i) vary according to a second order polynomial with the distance from the mouth of the watershed, ii) vary linearly with the distance from the outlet of the watershed, and iii) are constant throughout the watershed. Comparison of the results of the proposed equation with data from two experimental watersheds in Coastal British Columbia indicates that the three expressions of the proposed equation, even the simplest one assuming constant stream slope and roughness coefficient, are reliable and give good approximation of the observed time lag.
Design Values for Precipitation and Floods from M5 Values
Authors: Elíasson Jonas
Published: May 2018

The M5 method, originally proposed by the Natural Resource Council in UK, is used for estimating precipitation in Iceland. In this method the M5 (24-hour precipitation with 5-year return period) is used as an index variable. Instead of the usual approach in estimating regional values of the coefficient of variation another coefficient, Ci is used. The M5 and the Ci define together a generalised distribution that can be utilised to estimate the statistical distribution of precipitation anywhere in the country. M5 maps have been prepared for this purpose by the Engineering Research Institute of the University of Iceland. Methods have been devised to derive PMP values from the M5 values. This paper describes the method and gives examples of calculation. It is also shown that the same CDF applies for the observations of shorter duration precipitation available in Iceland. By applying the principle of identical statistical distribution for standardised annual maxima of any duration, IDF (Intensity – Duration – Frequency) curves have been derived. This allows the IDF – values to be calculated on basis of M5 and Ci, which are the two-parameters that define the generalised precipitation distribution.
Estimation of Regional Parameters in a Macro Scale Hydrological Model
Authors: Engeland Kolbjørn , Gottschalk Lars , Tallaksen Lena
Published: May 2018

Macro-scale hydrological modelling implies a repeated application of a model within an area using regional parameters. These parameters are based on climate and landscape characteristics, and they are used to calculate the water balance in ungauged areas. The regional parameters ought to be robust and not too dependent of the catchment and time period used for calibration. The ECOMAG model is applied for the NOPEX-region as a macro-scale hydrological model distributed on a 2×2 km2 grid. Each model element is assigned parameters according to soil and vegetation classes. A Bayesian methodology is followed. An objective function describing the fit between observed and simulated values is used to describe the likelihood of the parameters. Using Baye's theorem these likelihoods are used to update the probability distributions of the parameters using additional data, being it either an additional year of streamflow or an additional streamflow station. Two sampling methods are used, regular sampling and Metropolis-Hastings sampling. The results show that regional parameters exist according to some predefined criteria. The probability distribution of the parameters shows a decreasing variance as data from new catchments are used for updating. A few parameters do, however, not exhibit this property, and they are therefore not suitable in a regional context.