bluuebunny/crossref_metadata_2025 huggingface dataset:
The Application of Radioactive Tracers for Determination of Bed-Load Transport in Alluvial Rivers
Authors: Thomsen Thorkild
Published: May 2018

Radioactive isotopes have been applied for determining the transport rate of bed load in an alluvial river on the basis of: centroid velocity of the tracer particles, size and material-transporting width of mobile layer. These parameters were found by detailed measurements in the field. Computed values were produced on the basis of Engelund and Fredsøe's model on sediment transport (1976) and on the propagation of bed forms. When comparing measured and computed values, the difference was about 25%. Finally, the applicability of tracer methods for solving practical problems is discussed.
Diversion of the River Neva
Authors: Pedersen Flemming Bo , Møller Jacob Steen
Published: May 2018

Diverging part of the river Neva discharge to the dry regions in the southern USSR has raised the question, to what extent such a river diversion will influence the hydrographic conditions in the Baltic Sea and the Danish Inland waters. In order to quantify the influence, the system has been divided into eight subareas, each of which is characterized by an equation for the mass, the volume and the dynamic balance (the mixing), respectively. The man-made change in the river runoff has been introduced in the equations, which have then been linearized and solved with respect to changes in the salinities, the discharges and the layer depths in the system.

As a quantitative example the hydrographic consequences of a 25% reduction in the river Neva discharge have been outlined. The most pronounced influence is on the salinities, which are increased by 0.2 to 0.4 ‰ allover in the system. Hence, if the river diversion had become executed in the beginning of this century a 30 to 40% higher salinity-variation would have been encountered in the Baltic Sea – compared to the actual variations during this century.
Diverging Overland Flow
Authors: Singh V. P. , Agiralioglu N.
Published: May 2018

Kinematic wave theory is utilized to investigate diverging overland flow which does not appear to have been previously investigated in watershed hydrology. This paper is the first in a sequel of two. It developes analytical solutions for a diverging geometry for two cases: (1) when infiltration is considered through rainfall-excess, and (2) when infiltration is treated concurrently with runoff; this gives rise to a free boundary problem. Part II discusses the application of the proposed model to natural watersheds.
Extreme Rainfall Events in Lund 1979–1980
Authors: Niemczynowicz Janusz , Jonsson Olle
Published: May 2018

All raingauge measurements give only one-point values. Since the practical applications of rain data always deal with areal measures, the knowledge of areal distribution of rain is very important for correct evaluation of the rain volumes. Two types of rainfall input data are generally used: design rainfall hyetographs and long historical rainfall records. The third type of input data has to be recognized: the observed single rainfall event, during which the consequences such as runoff, flooding or pollution loads have been observed and recorded. Good areal characterization of such single event is necessary if the results are to be generalized.

In the paper a set of extreme rainfall events observed in Lund during a period of two years is presented. Point and areal intensities are presented for ten extreme events. Storm centered Areal Reduction Factors (AFR-s) calculated for different durations are also presented. Size, shape and movement of the raincells is discussed in the context of the meteorological background observed.
Effect of Scale on the Complexity of Snowmelt Systems
Authors: Braun L.N. , Slaymaker H.O.
Published: May 2018

During the melt season of 1978, the nature of snow and ice storage, the energy sources and the stream flow response were investigated at a site, a small-scale and a meso-scale watershed in the Coast Mountains of British Columbia, Canada. Differences in system internal homogeneity and system response times at each of these scales indicated the usefulness of this empirical classification. It is also demonstrated that different methods of analysis of snowmelt systems are appropriate at the different scales.
Infiltration Rates of Rainwaters in Sri Lanka Measured by Using Tritium Tracer
Authors: Dharmasiri J. K. , Dharmawardena K. G. , Wijesinghe M. W. P. , Thiranagama P. , De Mel I. D. T. , Wickremarchchi D. A. , Goel P. S.
Published: May 2018

Tritium tracer, injected below the surface soil, is used to follow the movement of soil moisture in the unsaturated zone at several geo-hydrologically different sites in Sri Lanka. Depth profiles of tritium activity and moisture contents have been measured after rainfall. For two well-established aquifers, Vanathavillu and Mannar, the recharge to groundwater is close to 30% of the rainfall. Infiltration is much higher. The moisture movement is apparently like piston flow. In the central highland regions, where the surface cover is composed of an overburden of fractured rocks overlain by a few metres of soil cover, the infiltration rate is very high.
A Numerical Model of Aquifer Tests in Multi-Layered Aquifer/Aquitard Systems
Authors: Mucha Igor , Kærgaard Henrik
Published: May 2018

A numerical model is presented, capable of computing drawdowns anywhere in a multiaquifer/aquitard system, resulting from pumping from a single well, screened in arbitrarily chosen aquifer(s) in the system. The model is of radial, symmetric type, in the sense that inhomogeneities in horizontal directions cannot be taken into account. The model was created primarily to compute the effects of any kind of stratification in an aquifer system on the results of pumping tests.

The computing principles are described, and drawdowns in a hypothetical system are computed to be compared with standard aquifer test formulas in order to illustrate the behaviour of the system.

The model is finally used for interpretation of two earlier reported aquifer tests from localities in Denmark.
Runoff Chemistry at a Mini-Catchment Watered with “Unpolluted Precipitation”
Authors: Christophersen N. , Stuanes A.O. , Wright R.F.
Published: May 2018

600 mm of artificial, “unpolluted” precipitation with a chemical composition of assumed preindustrial quality ([H+] = 9 μeql−1, [SO4] = 11 μeql−1) was sprayed on a “mini-catchment” (98 m2) over a period of 3½ weeks. The mini-catchment is a granitic bowl partially covered with shallow, acid soils. It is located in the Storgama area, Telemark county, southern Norway, an area which today receives acidic precipitation ([H+] = 54 μeql−1, [SO4] = 59 μeql−1).

The treatment resulted in lowered values for [H+], [Al] and [SO4] in runoff within a week. Excluding the spring snowmelt, [H+] ≈ 50 μeql−1 (pH = 4.3) under natural conditions, whereas during the experiment [H+] levelled off at 30 μeql−1 (pH = 4.5). Correlation analysis suggests that SO4 and organic anions are related to the runoff acidity. The level of total organic carbon in runoff was, however, elevated compared to undisturbed conditions. Under the present natural conditions S04 is the most important anion.

The amount of water-extractable sulfate in the soil is equivalent to about ½ of the present yearly input. The response in the sulfate output to a reduced input is difficult to predict because of processes which transform sulfur to and from various compounds in the soil and vegetation. Several years may be required before a new steady state is reached after a substantial decrease in input. Long-term experiments in which the catchment is shielded against natural precipitation are required to obtain more certain estimates of the response in runoff composition.
Water Resources Planning in the Suså-Basin by Means of a Simulation Model
Authors: Knudsen Jesper , Rosbjerg Dan
Published: May 2018

As part of the »Suså-project« a combined hydrological/water quality simulation model has been developed for water resource planning purposes. The model provides a detailed analysis of the consequences of meeting the demands of conflicting interests (water supply, waste water disposal, irrigation, recreation). The model is presented along with simulation results for a number of different dispositions of the water resource, in order to illustrate the applicability.
A New Technique for the Analysis of Extreme Rainfall with Application to Lagos Metropolis, Nigeria
Authors: Oyegoke E. S. , Sonuga J. O.
Published: May 2018

This paper focuses on the use of the principle of maximum entropy as an alternative technique for the parameter estimation of the Extreme Value Type – 1 (EV1) distribution or Gumbel distribution often used for the analysis and forecast of extreme events. A case study is made of storm rainfall analysis for Lagos metropolis using the available rainfall data for Ikeja, Oshodi and Lagos Mainland as obtained from Akanbi (1982).

For comparison purposes, the parameters of the EV1 distribution is also obtained using the Maximum Likelihood Method. The later being one of the most reliable techniques and perhaps the most widely used for parameter estimation of the EV1 distribution. This exercise has made it possible to demonstrate in some ways the superiority of the maximum entropy method over existing methods used for statistical simulation of extreme events.
Quantitative and Qualitative Characteristics of Urban Discharge to Small River Basins in the South West of Sweden
Authors: Hogland Wm. , Berndtsson R.
Published: May 2018

The paper deals with the qualitative and quantitative characteristics of urban discharge. Ratios for urban discharge and recipient flow during different time intervals are presented and discussed. The quality of the urban discharge is illustrated through pollutographs.
Dispersion of Pollutants in Semi-Infinite Porous Media with Unsteady Velocity Distribution
Authors: Kumar Naveen
Published: May 2018

Analytical solutions are developed for the dispersion problem in nonadsorbing and adsorbing, semi-infinite porous media in which the flow is one dimensional and the average flow velocity is unsteady. The expression that states the direct relationship of the dispersion coefficient with seepage velocity is used to solve the unsteady dispersion flow problem by introducing a new time variable. The source concentration of the pollutant varies exponentially with time. The variation in seepage velocity with time is considered because of resistance in the flow. The graphical solutions are also obtained for a set of data assumed.
On the Role of Equilibrium Reactions in Bore-Hole Waters in the Skellefte-Field, Northern Sweden
Authors: Lidén Jan , Sjöberg Staffan
Published: May 2018

In a series of bore holes in an acid-intermediate volcanite rock type measurements of pH and pe (in situ), main ionic constituents, silicic acid and aluminium were made. The bore holes covered the pH interval 6.5-8.6, each with a time invariant solution composition. Field data were used as an experimental test of computerized simulation of weathering reactions by means of equilibrium models. The results suggest that a criterion for an undisturbed groundwater system is a high pH and a low pe where the dissolved main components reach a saturation concentration close to that experimentally found. For lower pH values, however, only the subsystem H+ - Si(OH)4 - Al3+ corresponded to an equilibrium behaviour.
A State Model for Infiltration
Authors: Pingoud Kim , Jussi Orava P.
Published: May 2018

A state model for infiltration based on a spatial discretization of partial differential equations of vertical water movement in unsaturated homogeneous soil is presented. A transformation of the spatial coordinate is made in the basic equtions, thus allowing the representation of a semi-infinite soil in the state form. The aim of the model is to describe the dynamical relationship between ponding conditions in the catchment and infiltration during highly variable rainfall rates so that the model can be used flexibly as a part of larger, rainfall-runoff models. The relation of the present model to the conventional use of Philip's equation is considered. An approximative way to combine the infiltration model with a surface runoff model including many subcatchments is presented, in which the number of state variables in the combined model is reduced. Some features of the state model are discussed by using numerical examples. The behaviour of the combined model including infiltration and surface runoff parts is also compared with simulation results in the literature.
The Summer Water Balance in a Danish Oak Stand
Authors: Rømer Rasmussen K. , Rasmussen S.
Published: May 2018

The summer water balance in a Danish oak forest was studied during a period of 5 years. Interception reduces rainfall inside the forest by about 15%. Variations of the saturated soil moisture amount to some 10% of the water available to plants. Nevertheless, in most summers low soil moisture only restricts evapotranspiration during July. Insufficient leaf area is a major factor in restricting evapotranspiration: oak leaves develop late, and defoliation by insects also has a noticeable effect. The difference between potential and actual evapotranspiration normally ranges between 50 and 100 mm but reached 150 mm in 1976. Yet even in this dry year the vegetation recovered at once as soon as the water stress had been removed.
A Study of Soilwater and Groundwater Flow of Hillslopes – Using a Mathematical Model
Authors: Johansson B.
Published: May 2018

The soil and groundwater flow of a hillslope adjacent to a stream has been studied using a physically based mathematical model. Values of soil parameters have been taken from investigations of Swedish till soils. Model simulations have been made in order to calculate groundwater outflow during and after a rainfall event, and to study the response to infiltration of soil and groundwater flow in different parts of the slope. The effects of soil layering and slope configuration have also been studied.

The simulated peak of groundwater outflow, occurring just after cessation of infiltration, is of the same order of magnitude as a typical streamflow peak in a small Swedish watershed. The increase of groundwater outflow during and after a rainfall event is, according to model simulation, caused by infiltration close to the stream. Hence, the soil properties of this part of the slope are of great importance to runoff generation.
Modeling the Hydrologic Cycle: The MC Model
Authors: Deschesnes J. , Villeneuve J.-P. , Ledoux E. , Girard G.
Published: May 2018

The MC model, developed to simulate the simultaneous movements of surface and groundwater flows in a watershed, is applied to three different types of watersheds to demonstrate its characteristics and its flexibility of use. The first case reports on an application where the surface flow and the groundwater flow are of the same importance, the second case reports on one where the surface runoff dominates and lastly we present a study where the groundwater flows are dominant. In each case, we place emphasis on how the MC model can integrate the hydrological system under study for an accurate representation of reality. Examples of results are also included.
Analysis of Non-Linear Rainfall-Runoff Process
Authors: Hager Willi H.
Published: May 2018

Rainfall runoff phenomena in small watersheds are favorably modelled using the kinematic wave approach. The present investigation considers excess rainfall as time dependent but ignores spatial effects. Solutions of a recent approach are analyzed for a complete cascade consisting of catchment area and small stream. Typical cases are discussed and results include predictions of maximum discharge at the watershed outlet, corresponding time to peak and the overall description of the resulting hydrograph. Criteria concerning the applicability of the kinematic wave approach are given, and examples illustrate the computational procedure.
Base Flow and Water Supply
Authors: Dahl N. J.
Published: May 2018

The interaction between the base flow created by seepage through the unsatu++rated zone in a region between two parallel rivers and the flow caused by the gaining of water from wells positioned at arbitrary points over the region is analysed. Normally both flows are non-steady but, for the sake of simplicity, the base flow is here assumed to be steady whereas the yield of water from the single well is assumed to be a free function of time defined by the actual consumption which assumption leads to a non-steady flow towards the wells. A special result of the analysis is that it becomes possible to define the catchment area of the single well.
Run Analysis of Rainfall Data Affected by Urbanization
Authors: Rao Srinivas G. , Ramachandra Rao A.
Published: May 2018

Urbanization generally increases the amount of rainfall in urban areas and/or downwind areas of urban centers. This paper investigates whether urbanization significantly changes the run properties of rainfall. Three run properties, the run-length, run-sum and run-intensities of positive (surplus) and negative (deficit) runs, of the annual and monthly rainfall are evaluated by using the theory of runs. The annual rainfall is assumed to be normally or gamma distributed, and the monthly rainfall is assumed to follow a two-state Markov chain with stationary, transition probabilities. The methology is applied to annual and monthly rainfall data at La Porte and three surrounding stations in Indiana. The results indicate that these assumptions are adequate to characterize the annual and monthly rainfall. The study demonstrates that although urbanization has inadvertently increased the rainfall amounts at La Porte in relation to its surrounding stations (the so-called La Porte anamoly) the run properties at La Porte are not significantly different from those at the surrounding stations. Further it is found that the run-intensity is a better indicator than run-length or run-sum for evaluating the effects of urbanization on rainfall.
Frazil Measured in the Laboratory and in the Field
Authors: Tsang Gee
Published: May 2018

Using an instrument that was recently developed at the National Water Research Institute, the concentration of frazil in flowing water was measured under laboratory conditions for both fresh water and sea water and under natural conditions in the Beauharnois Canal. Experimental data and their analysis are reported in this paper.
Multivariate Transfer Function-Noise Model of River Flow for Hydropower Operation
Authors: Olason Tryggvi , Watt W. Edgar
Published: May 2018

The formulation of multivariate autoregressive moving average (ARMA) time series models and their transfer function noise (TFN) form is described. Development of a multivariate TFN model is difficult if the multiple inputs are correlated. Various methods for developing a multivariate TFN models with correlated multiple inputs are critically reviewed. A simple approach to developing multiple input TFN models with correlated inputs is described. This approach is successfully applied to developing a forecasting model for average daily flow of the Mattagami River at Little Long Generation Station in Northern Ontario, Canada. System inputs are upstream and tributary flows. Only three years of daily data for the period April 1st to October 31st were required to calibrate the model. Two further years were used to verify the model. Forecasts at lead times of one and two days were good for both calibration and verification periods. The average standard errors were 8% of average inflows (1-day lead) and 18% (2-day lead). The system produces significantly better forecasts than a univariate time series model.
New Procedures for Flood Estimation in Norway
Authors: Sælthun N. R. , Andersen J. H.
Published: May 2018

The paper describes the development of new procedures for flood estimation for dam design in Norway. It summarizes the regulations and recommendations for flood calculations set forth by “The Norwegian Regulations for Planning, Construction and Operation of Dams” and the recent guidelines issued by the Hydrological Department of The Directorate of Water Resources.
Hydrological Maps Development of a System for Calculation and Presentation
Authors: Johansson B. , Jutman T.
Published: May 2018

Increasing attention is paid to problems concerning water resources planning. It is essential that the hydrological information required is available to the planner in a form that facilitates combination with other types of information.

This paper describes the development of a system for calculation and presentation of regional and comprehensive hydrological information. Main components of the system are the interpolation routines, a water balance model adapted to the space and time scale and a data base for supporting information. Examples of presentations are given.
Modelling of Unsaturated Flow in Heterogeneous Soils
Authors: Høgh Jensen K.
Published: May 2018

Water flow and solute transport in the upper soil layers are processes which are of importance in many hydrological and agricultural applications. These processes are occurring in a medium which has a complex composition, since the soil is a product of both the geological formation history and various man-induced activities like agricultural development. In addition, the upper soil is subject to cyclic variations in water content in response to the variable exposure of rainfall and outer evapotranspiration demand.

The paper describes simulations of the field conditions at different points within two research fields where comprehensive field investigations have been carried out. The simulations are based on solutions to the partial differential flow equation, subject to the measured climatic conditions and the hydraulic properties in the individual soil columns. The simulations of water content and capillary pressure are compared with measurements.
Transformation of Input to a Stochastic Model using a Distributed Deterministic Model
Authors: Snorrason Á. , Einarsson K.
Published: May 2018

In recent years, hydrologists have attempted, with encouraging results, to synthesize the accomplishments of time series analysis and deterministic systems methods into the more general framework of stochastic dynamic systems. The purpose of this paper is to attempt an improvement of a stochastic time series model by the use of inputs generated by a distributed, deterministic model.

The analysis is based on a simplified transfer function-noise model, where the system output is modeled as a linear combination of present and past inputs as well as past outputs.

The systems chosen for the analysis are two partially glaciated basins in Iceland.

The results were in general promising and showed that a careful selection of input series could overcome to a great extent the non-linearities as well as the non-stationarities in the relationship between discharge and meteorological variables. The results also showed that transformation of the meteorological series using distributed, deterministic techniques gave superiour results, compared with the standard degree-day approach.
River Flow with Excessive Suspended Sediment Load
Authors: Andreasson P. , Sellgren A.
Published: May 2018

River flows with high volume concentrations (20-50%) of silty sediments generally imply that the mixture has non-Newtonian properties. In this study, the rheological behaviour of mixtures with solids particles smaller than 0.1 mm was identified experimentally with viscosimeters. Characteristic flow parameters, such as energy losses and depths, were then determined in several examples for turbulent open channel flows.
Geothermal Reservoir Engineering Experience in Iceland
Authors: Kjaran Snorri Páll
Published: May 2018

Geothermal reservoir engineering studies have been carried out in Iceland for years concurrently with the utilization of the various geothermal fields. This has been essential in order to understand the responses of the reservoirs to exploitation. The importance of geothermal energy has grown steadily in the past decades relative to other primary energy resources, providing at present about 40% of the total energy consumed in Iceland. In this article the experience gained from exploiting Icelandic geothermal reservoirs is reviewed. The geological setting of the hydrothermal system is described as well as geophysical exploration methods. Several field examples are presented, demonstrating the effects that exploitation has on the geothermal reservoir's response.
Snow Distribution on Forest Clearcuts in the Swedish Mountains
Authors: Zakrisson Kurt-Åke
Published: May 2018

The paper is focused on the problem of choosing observation localities at the margin of forests for snow surveys. A systematic study was made of differences in snow depth and water equivalents of snow accumulation near the boundaries between forests and open land. The field data were collected during the winter seasons 1983-84 and 1984-85.

The study involves sounding snow depths and calculating water equivalents of the snow cover from profiles crossing distinct boundaries between forests and clearcuts. The snow accumulation was found to be relatively large in a zone up to 40 m just outside the forest boundary. The accumulation up to 15 m just inside the forest boundary was relatively small as compared to the forest in general.

A slight excess of snow in the forest compared to the clearcuts, established at the beginning of the snow accumulation season, gradually turns into a small deficit in April. During most of the melting season the amount of snow in the forest is considerably bigger than in the clearcuts.
A Perturbation Based Model of Heat-Induced Suppression of River Ice
Authors: Sarraf S. , Saleh W.
Published: May 2018

The study of the thermal response of ice covered streams to an effluent of high temperature, or of fast moving water, has been of considerable interest to those concerned with hydraulic systems, environmental effects, and navigational routes in cold regions. The discharge of tributary thermal effluents into cold region rivers may alter the thermal and hydrodynamic conditions of ice cover progression and create reaches of open water in the ice throughout the winter season. An analytical approach, based on pertubation techniques, has been developed and tested concerning the suppression of ice cover and the migration of its fronts. The upstream and the downstream ice edges are determined for two cases of steady non-uniform flow. Conditions for the suppression of the ice cover are also obtained based on the relative positions of the upstream and downstream ice edges. Comparison with field data shows a good agreement with the formulation incorporating the thermal effluent velocity.
Environmental Impacts of an Old Mine Tailings Deposit — Metal Adsorption by Particulate Matter
Authors: Karlsson S. , Sandén P. , Allard B.
Published: May 2018

The distribution of metals (aluminum, manganese, iron, copper, zinc, cadmium and lead) between suspended particles and solution phase has been studied by analysis of time series data in a stream receiving leachates from a mine tailings deposit. A precipitation of aluminum and iron takes place when the acidic effluents are neutralized by unpolluted groundwater, while the other dissolved elements never reach saturation. The particulate fraction is largely amorphous. A transfer of dissolved elements from the solution phase to the particle phase, increasing in the order zinc < cadmium < copper < lead with increasing pH, is observed. This removal of metals from the aqueous phase appears to be due to sorption processes rather than to coprecipitation. The formation of a particulate metal fraction could be the means for long-range transportation and redistribution of metals in environmental water systems.
Spatial Distribution of Pre-Warm Front Rainfall in the Mediterranean Area
Authors: Corradini C. , Melone F.
Published: May 2018

Evidence is given of the distribution of pre-warm front rainfall at the meso-γ scale, together with a discussion of the main mechanisms producing this variability. An inland region in the Mediterranean area is considered. The selected rainfall type is commonly considered the most regular inasmuch as it is usually unaffected by extended convective motions. Despite this, within a storm a large variability in space was observed. For 90% of measurements, the typical deviations from the area-average total depth ranged from - 40 to 60 % and the storm ensemble-average rainfall rate over an hilly zone was 60 % greater than that in a contiguous low-land zone generally placed upwind. This variability is largely explained in terms of forced uplift of air mass over an envelope type orography. For a few storms smaller orographic effects were found in locations influenced by an orography with higher slopes and elevations. This feature is ascribed to the compact structure of these mountains which probably determines a deflection of air mass in the boundary layer. The importance of this type of analysis in the hydrological practice is also emphasized.
Chemistry and δ13C of Total Dissolved Carbon in Waters of Selected Springs nearby Lublin City
Authors: Staniaszek P. , Halas S.
Published: May 2018

The pH, δ13C of total dissolved carbon and HCO3−, Ca2+, Ca2+ + Mg2+ contents in spring waters were investigated. Changes of these values were recorded for 8 months of 1982 and 1983. The changes were irregular and larger in winter and early spring, than in autumn and late spring. These changes and a longterm trend observed in October and November are discussed in terms of models of Deines et al. (1974) and the theory of mixing of waters (Wigley and Plummer 1976).
An Application of Kriging to Rainfall Network Design
Authors: Shamsi U.M. , Quimpo R.G. , Yoganarasimhan G.N.
Published: May 2018

Universal kriging techniques based on the generalized covariances corresponding to IRF-k theory, are applied to analyze the design of raingauging networks in regions where the spatial mean is not constant. The objective is to obtain an optimal estimate of watershed precipitation. For the purpose of analysis, symmetric and asymmetric hypothetical rainfall fields are considered. The hypothesized storms provide the bases for comparing the results of the analysis. The results are also compared with traditional approaches in current use. The investigation depicts the superiority of kriging techniques over the other methods. The effect of storm spatial variability on the network design is also examined.
Over-Winter Chemistry of Subarctic Fens, Eastern Canada
Authors: Kingsbury C. M. , Moore T. R.
Published: May 2018

Two subarctic fens (one nutrient-poor, one nutrient-rich) were sampled from October, 1984 to July, 1985 near Schefferville, northern Quebec. The changes in concentations of chemicals (pH, conductance, Ca, Mg, Na, K, Fe, dissolved organic carbon, P, NH4+-N and N03−-N) dissolved in the peat water were identified during the freeze-thaw cycle. The highest chemical concentrations were in the winter (associated with the ice formation process), followed by the spring-summer, then fall. Four main processes influenced the concentration of dissolved chemicals in subarctic fens: 1) Snowmelt diluted the peat water; 2) Freezing of the peat increased concentrations of dissolved nutrients and other chemicals, believed to originate from biological sources; 3) Further increases in concentrations over the winter were caused by the incorporation of peat water, which migrated into the frozen peat; 4) Thawing of peat influenced the water chemistry by combining the release of the above 3 processes, along with biotic utilization. The freeze-thaw cycle in the subarctic fens appeared to increase the availability of important nutrients (such as phosphorus) during the spring.
Soil Moisture Deficits in South-Central Sweden
Authors: Andersson Lotta
Published: May 2018

Some commonly used assumptions about climatically induced soil moisture fluxes within years and between different parts of a region were challenged with the help of a conceptual soil moisture model. The model was optimised against neutron probe measurements from forest and grassland sites. Five 10 yrs and one 105 yrs long climatic records, from the province of Östergötland, situated in south-central Sweden, were used as driving variables. It was concluded that some of the tested assumptions should not be taken for granted. Among these were the beliefs that interannual variations of soil moisture contents can be neglected in the beginning of the hydrological year and that soils usually are filled up to field capacity after the autumn recharge. The calculated climatic induced dryness was estimated to be rather insensitive to the choice of climatic stations within the region. Monthly ranges of soil moisture deficits (1883-1987) were shown to be skewed and it is therefore recommended to use medians and standard deviations in statistical analyses of “normal” ranges of soil moisture deficits.
Regional Exceedance Probabilities
Authors: Gottschalk Lars
Published: May 2018

Construction of a regional flood frequency curve is based, as a rule, on fitting this curve to representative quantiles. In a regional sample of floods the probability of extreme values corresponding to return periods, that exceed the record lengths, is much larger than that of individual series, used to determine the representative quantiles. The probabilities of exceedance of regional extremes can be calculated straightforward in case of independent data, applying the theory of order statistics. For regionally dependent data one can define an equivalent number of independent regional series and then utilize the theory for independent data. This approach is exemplified with flood data from Norway.
Proposed Swedish Spillway Design Guidelines Compared with Historical Flood Marks at Lake Siljan
Authors: Harlin Joakim
Published: May 2018

A comparison between the proposed Swedish spillway design floods and historic flood marks made at lake Siljan in central Sweden, is shown. Frequency analysis is performed incorporating pregauge information on water levels together with a sensitivity analysis of modelling assumptions.

A water level of 0.42 to 0.75 metres above the highest historic flood mark (166.10 m.a.sl., 1659) was obtained when routing the design spring flood through lake Siljan. The design autumn flood lifted the lake to 1.56 to 1.52 metres below the highest flood mark. Return period for the design spring and autumn flood was estimated to about 1,000 years. The uncertainty in frequency analysis proved to have larger impact than modelling assumptions on estimating the risk of the design flood.
Methods Used for Calculation of Plant Available Water in Nordic Till Soils
Authors: Madsen Henrik Breuning , Riley Hugh , Lundin Lars
Published: May 2018

This paper describes different methods used in the Nordic countries for calculation of the storage capacity of tills for water available for plant production. The purpose of the paper is to give an overall review of the state of art for calculating the plant available water in Nordic tills. The paper is therefore based on already published data and a comprehensive list of references is given.
Condensation of Humidity onto a Snow Covered Roof
Authors: Nordell Bo
Published: May 2018

In an approach to explain why snow loads on roofs increase when an early melting period occurs, the increased snow load is seen as condensation of humidity of the air onto snow covered roofs. 2-D simulations were performed with the Fluent model. The humidity of the air is considered as small droplets. The condensation rate is 3-5 kg/m2 h. The simulations show that the wind side of the roof is more subjected to condensation than the lee side. This study indicates that short-term condensation onto snow covered surfaces should be paid more attention.
Sample Functions as Indicators of Aquifer Heterogeneities
Authors: Şen Zekâi , Al-Baradi Abdulaziz
Published: May 2018

An adaptive slope matching method is used to evalute the aquifer heterogeneity from constant rate aquifer test data. The basic aquifer parameters such as the storativity and transmissivity are considered to vary spatially and the effects of such changes appear as temporal variations during a pumping test period. It is stressed that this is due to the depression cone expansion with time around the pumping well. The plots of individual parameters versus time are referred to as the sample functions. These functions have erratic variations indicating that the aquifers considered in this study have local heterogeneities. Furthermore, a moving average technique is applied to each parameter sample function for the purpose of finding regional trends in the parameter variations. It is interesting to notice that the arithmetic average values of sample functions yield aquifer parameter values as obtained by the classical type curve matching techniques which assume that the aquifer concerned is homogeneous. Hence the use of the sample function concept is recommended for the detailed interpretation of the aquifer heterogeneity.
Equilibrium Speciation Models for Hg, Cd, and Pb in the Gulf of Bothnia and its Catchment Area
Authors: Gunneriusson Lars , Sjöberg Staffan
Published: May 2018

Equilibrium speciation models were established for Hg (II), Cd (II) and Pb (II) in bog-, river- and sea water having a composition corresponding to that of the Gulf of Bothnia (6 ‰ salinity). The calculations were performed using the computer program SOLGASWATER. The models were based on available thermodynamic data at 25°C and included the inorganic ligands OH−, Cl−, Br−, HPO42− and CO2 (aq). Furthermore, complex formation with organic substances originating from a bog water was considered, Mg (II) and Ca (II) were also included as competing cations. All water types were assumed to be oxic and in equilibrium with atmospheric carbon dioxide, 10−3.5 atm (32 Pa).

The calculations showed that the speciation of Hg (II) and Pb (II) in bog and river waters is dominated by complexation with the organic substance, except for lead (II), where the Pb2+ -ion dominates at pH⩽5. In the Gulf of Bothnia, the chloro complexes HgCl2 and HgCl3− becomes prevailing as the salinity increases. Besides Pb2+, the species PbCl+ and PbCO3 become important upon increasing the salinity and pH. The dominating fraction of Cd (II) is Cd2+ in bog water, in river water and in waters of salinity lower than 4.5 ‰.

With increasing salinity CdCl+ and CdCl2predominate.
Transposition of Monthly Streamflow Data to Ungauged Catchments
Authors: Gan K.C. , McMahon T. A. , O'Neill I.C.
Published: May 2018

Various forms of the regressional relationship between the concurrent monthly discharges of neighbouring catchments are explored, with a view to generalising the relationship for a region. This enables monthly streamflow data to be transposed from a gauged catchment to an ungauged catchment, provided that certain transfer coefficients can be estimated from the physical catchment and rainfall characteristics. Most of the methods are based on a linear relationship between the concurrent monthly discharges of a pair of catchments with only one transfer coefficient. This may be estimated in a number of ways for a pair of gauged-ungauged catchments, however, errors in the individual transposed flows are high.
An Improved Rational Method for Urban Runoff Application
Authors: Lyngfelt Sven
Published: May 2018

In the initial stages of drainage systems planning and for independent tests of advanced runoff model performance there is a need for a simple point flow model. In these cases a method is proposed which is an improved version of the traditional Rational Method. The method, usually regarded as empirical, has a certain relationship with the kinematic wave theory. It is then discussed from both a theoretical and practical point of view based on comparisons with the performance of an advanced continuous model.
Drawdown Distribution During Recovery around a Large Diameter Well
Authors: Şen Zekâi
Published: May 2018

An analytical solution is presented for the drawdown distribution in a large diameter well during recovery. It takes into consideration the well storage. A set of type curves are given to determine the transmissivity and storage coefficient of the aquifer. The basis of the methodology is to solve simultaneous differential equations of the water balance and Darcy laws. The application of developed methodology has been given for recovery data from India and Saudi Arabia.
Spatial Variability of Physical Parameters and Processes in Two Field Soils
Authors: Høgh Jensen K. , Refsgaard J. C.
Published: May 2018

A numerical analysis of solute transport in two spatially heterogeneous fields is carried out assuming that the fields are composed of ensembles of one-dimensional non-interacting soil columns, each column representing a possible soil profile in statistical terms. The basis for the analysis is the flow simulation described in Part II (Jensen and Refsgaard, this issue), which serves as input to a transport model based on the convection-dispersion equation.

The simulations of the average and variation in solute concentration in planes perpendicular to the flow direction are compared to measurements obtained from tracer experiments carried out at the two fields. Due to the limited amount of measurement data, it is difficult to draw conclusive evidence of the simulations, but reliable simulations are obtained of the mean behaviour within the two fields.

The concept of equivalent soil properties is also tested for the transport problem in heterogeneous soils. Based on effective parameters for the retention and hydraulic conductivity functions it is possible to predict the mean transport in the two experimental fields.
Uniform Horizontal Groundwater Flow against Dispersion in a Shallow Aquifer: Two Analytical Models
Authors: Vinda Ram Raj , Yadava Raja Ram , Kumar Naveen
Published: May 2018

Analytical solutions converging rapidly at large and small values of times have been obtained for two mathematical models which describe the concentration distribution of a non reactive pollutant from a point source against the flow in a horizontal cross-section of a finite saturated shallow aquifer possessing uniform horizontal groundwater flow. Zero concentration or the conditions in which the flux across the extreme boundaries are proportional to the respective flow components are applied. The effects of flow and dispersion on concentration distribution are also discussed.
Probable Maximum Precipitation in Iceland – Station Values –
Authors: Elíasson Jónas
Published: May 2018

The meteorological stations in Iceland are rather few compared to the size of the country, and their service time is short compared to other developed countries. Investigations of individual 24-hour station PMP values computed by the Hershfield and NERC methods show trends that are important for the application of PMP values in engineering design. The results fall into two series, one with high PMP values and the other with lower values. The low values originate from station groups situated in areas with mildly sloping terrain and here the results compare fully with what should be expected from experience from other countries. The other series shows results that do not compare as well with previously published results. Their general characteristics is that PMP values calculated hy the Hershfield method are of the order 80% higher than the corresponding results obtained by the NERC method. The results of this high series do not check against results obtained from meteorological models. It is noteworthy, that all the stations of the low series belong to station groups where the terrain is gently sloping, i.e. average terrain slopes less than 1.4%, while in the high series all the stations belong to station groups where the terrain slopes steeply from a highland plateau down to sea level. It is concluded that the generalized estimates of PMP values needed in engineering design could be obtained.
The Influence of Basin Aridity on the Efficiency of Runoff Predicting Models
Authors: Mimikou M. A. , Hatjisava P. S. , Kouvopoulos Y. S. , Anagnostou E. N.
Published: May 2018

The connection between runoff predicting models efficiency and basin aridity is investigated by using data from five representative basins in the mountainous central and northern Greece. Two substantially different models were selected, a monthly water balance model and an empirically fitted rainfall runoff model of the Kalman filter type. Both models were calibrated and validated in each basin and their overall efficiency was evaluated for each basin. The five basins were classified by using a humidity index and were found to range from humid to semi-arid. The efficiency of each model was then tested in terms of decreasing aridity and the two models exhibited a clearly contrasting behaviour; a decreasing efficiency of the Kalman filter model was observed, whereas the water balance model efficiency showed to increase with decreasing aridity. This behaviour is explained by considering the autoregressive characteristics of the corresponding five runoff time series, which are imparted in them by the filtering action of the basin. This factor becomes more important the more arid the basin is. Conclusively, the model of the Kalman filter type, designed to take account of the runoff autoregression, is shown to perform better with increasing aridity while in contrast, the water balance type of model where runoff memory is not accounted for, performs better the more humid the basin is, hence the runoff autoregressive characteristics become less significant.
Representation of Infiltration in Adaptive Rainfall – Runoff Models
Authors: Corradini C. , Melone F.
Published: May 2018

The reliability of the extended Time Compression Approximation (TCA), commonly adopted in watershed models in order to represent the infiltration associated with erratic rainfalls, is investigated. This approximation is considered as a component of an adaptive real-time flood forecasting model. The forecasted flows are compared with those obtained replacing the extended TCA with the Complex Storm Point Infiltration Model (CSPIM) recently proposed by Smith et al. (1993). The discharge forecasted through the infiltration component based on the numerical solution of Richards' equation is used as a bench mark. The models were applied to situations representative of real areas in Central Italy. The CSPIM based watershed model was found to provide excellent results. The TCA based model, in spite of the adaptive component, yielded poor results for various rainfall patterns. However, it seems to be a reasonable approximation when a uniform rainfall spatial distribution is involved.
Improvements of Runoff Models What Way to Go?
Authors: Andersson Lotta
Published: May 2018

Model performance before and after the introduction of some alternative routines for calculation of evaporation, snow accumulation and melt with the PULSE/HBV runoff model were compared. The results showed that improvements were, in the best cases, small. Sometimes model fits deteriorated as a result of increased model complexity. On the basis of these, and from other experiences of attempts of model improvements, the success potentials for various efforts of model sophistication are discussed. It is hypothesised that model improvement cannot be achieved by increasing the complexity of some sub-routines, without considering the problems that are linked to spatial resolution of driving variables and the spatial distribution of physiographic parameters. It is suggested that physically based and conceptual schools of modelling can meet in a landscape mosaic context, with development of distributed models, based on information generally available from maps, remote-sensing images and meteorological stations.