bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Flood Flow Estimation
Authors: Reinius Erling 
Published: May 2018

The frequency analysis of flood flows recommended in textbooks yields different results by the graphical method of plotting on probability paper using e.g. the Weibull plotting position formula and the analytical method assuming e.g. log-normal or log Pearson type III distributions. If both methods were correct, the results of the two methods should be identical.
The plotting position formulas assume that the plotting position should coincide with the mean (or median) of the probabilities which the observation of a rank m has in a great number of samples, each of the same size N. A study of the problem by using synthetic samples shows that these positions do not coincide with the line of the population.
A further study shows, however, that the positions of the probabilities of the expected – mean – values of the largest, next largest etc. observation coincide with the line of the population. Thus, it is not the mean value of p of a rank m, but the value of p of the mean value of log q of the rank m, which agrees with the line of population. Therefore, the author finds it essential that the logarithm of the annual peak flows obtain a plotting probability equal to the probability of the expected value of the logarithm of the observations. A new plotting position formula which corresponds to the probability of the expected values of log q is derived.
A Comparison of Some Methods of Deriving the Instantaneous Unit Hydrograph
Authors: Singh V. P. , Corradini C. , Melone F. 
Published: May 2018

The geomorphological instantaneous unit hydrograph (IUH) proposed by Gupta et al. (1980) was compared with the IUH derived by commonly used time-area and Nash methods. This comparison was performed by analyzing the effective rainfall-direct runoff relationship for four large basins in Central Italy ranging in area from 934 to 4,147 km2.
The Nash method was found to be the most accurate of the three methods. The geomorphological method, with only one parameter estimated in advance from the observed data, was found to be little less accurate than the Nash method which has two parameters determined from observations. Furthermore, if the geomorphological and Nash methods employed the same information represented by basin lag, then they produced similar accuracy provided the other Nash parameter, expressed by the product of peak flow and time to peak, was empirically assessed within a wide range of values. It was concluded that it was more appropriate to use the geomorphological method for ungaged basins and the Nash method for gaged basins.
Modelling Water Exchange and Transit Times in Till Basins Using Oxygen-18
Authors: Lindström Göran , Rodhe Allan 
Published: May 2018

The application of hydrological models to data on conservative tracers can yield information about transit times and storage volumes and may provide an independent test of the model structure.
In this study, the PULSE-model has been modified to simulate conservative tracers. Attempts have been made to describe both short-term and long-term variations in oxygen-18 concentration in three small forested basins.
The performance of the model was considerably increased, when additional storage was introduced in the model. The turnover times were estimated to approximately 7 and 12 months for two of the basins.
Saturated Hydraulic Conductivity of Scandinavian Tills
Authors: Lind Bo B. , Lundin Lars 
Published: May 2018

There is a distinctive difference in hydraulic properties between the upper horizons of Scandinavian till soil and the deeper C-horizon. The hydraulic conductivity has been studied in different soil profile types, mainly Podzolic variants. In the topsoil there are correlations from grain size and porosity to hydraulic conductivity. Both porosity and hydraulic conductivity are stratified with depth. Often high conductivity appears in the upper soil horizons decreasing with depth to low values at about one metre. This pattern varies with soil type. The soils vary with topographic location as does the groundwater level.
Published data on hydraulic conductivity in the C-horizon of sandy-silty tills in Scandinavia covers a wide range, from about 5 × 10−9 m/s to 5 × 10−4 m/s, with a mean of 3 × 10−6 m/s. The correlation between porosity and hydraulic conductivity, as well as between mean grain size and hydraulic conductivity, is weak in the C-horizon. It is concluded that the sediment structure has a decisive influence on the hydraulic conductivity of till. A model of the relationship between fabric (in relation to water flow direction), the porosity in the poresize interval 30-95 μm and the hydraulic conductivity is presented.
A Review of Techniques used by Canada and other Northern Countries for Measurement and Computation of Streamflow under Ice Conditions
Authors: Pelletier Patrice M. 
Published: May 2018

In Canada, Water Survey of Canada, a division of the Water Resources Branch of Environment Canada, is responsible for the collection and processing of data from more than 3,300 active streamflow, water level and sediment data gauging stations. Because of the climatic conditions prevalent in Canada, an important part of the monitoring program is conducted under winter ice conditions. The determination of daily streamflow records during the winter period is important for several practical purposes, in particular for water power development. Essential to the computation of daily discharge records, are reliable streamflow measurements. However, discharge measurements under ice conditions are generally difficult to obtain because of severe weather conditions, hazardous field conditions, and ill-adapted field measurement techniques.
In this paper, the field methods and instruments, and computational methods used by Water Survey of Canada for streamflow measurement and computation under ice conditions are reviewed. Factors affecting the accuracy of discharge measurements performed under ice conditions are discussed. Newly developed instruments for use under ice conditions are described and their advantages discussed. A comparison between techniques used by Canada and other northern countries is also given. Areas of research and investigations for improvement in the overall quality of data are suggested.
Spatial Variability of Physical Parameters and Processes in Two Field Soils
Authors: Høgh Jensen K. , Refsgaard J. C. 
Published: May 2018

The horizontal variability of soil hydraulic parameters, water content and suction measured within two research fields in Denmark is analyzed and discussed.
A numerical analysis of the flow in the two spatially heterogeneous fields is carried out by 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. Flow predictions based on the classical Richards' equation are carried out for all columns, and the mean and standard deviation of water content and suction in planes perpendicular to the flow direction is derived and compared to measurements. The analysis shows that the model to a reasonable degree is able to describe most of the variation in flow variables within the two fields.
The concept of equivalent soil properties is also investigated and applied to the two fields. Based on the average retention properties it is possible to predict the horizontal averages of flow variables within the fields.
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).
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.
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.
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.
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.
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.
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.
Improved Measurements and Analysis of Spatial Snow Cover by Combining a Ground Based Radar System With a Differential Global Positioning System Receiver
Authors: Marchand Wolf-Dietrich , Bruland Oddbjørn , Killingtveit Ånund 
Published: May 2018

The paper describes the realization of a new snow measurement system where a Ground Penetrating Radar (GPR) is connected to a Differential Global Positioning System (DGPS) receiver. A snow scooter pulled a radar antenna, a distance wheel triggered the radar pulses and the reflections were stored in a control unit. A marker was set on the radar file each time a position was logged on the DGPS receiver. Thus, each position was directly related to a snow depth measured by the GPR. The obtained accuracy of the position was in the range of 5-10 m and manual calibration measurements were used to ensure good quality of the snow depth data.
The system was tested in the Norwegian catchment Aursunden during the period of maximum snow accumulation, 12th – 23rd April 1999. Landscape features were analyzed with a Geographic Information System (GIS) and extensive snow measurements were worked out in representative areas. The obtained data on the snow cover were later used for statistical analysis.
In addition to the efficiency which makes it possible to measure large areas in a relatively short time, the major advances in the described system is that the obtained data can be used directly in a computer aided GIS. Nevertheless, further improvement is needed because of 1) the possibility for ambiguous connection between snow depth log and position log, 2) the distance between consecutive positions is not constant since it is time dependent, 3) the algorithm for automatically detection of the ground reflection from the radar log-file still needs interference from the user.
Precipitation Estimates over the Baltic Sea: Present State of the Art
Authors: Rutgersson Anna , Bumke Karl , Clemens Marco , Foltescu Valentin , Lindau Ralf , Michelson Daniel , Omstedt Anders 
Published: May 2018

Precipitation is one of the main components in the water balance, and probably the component determined with the greatest uncertainties. In the present paper we focus on precipitation (mainly rain) over the Baltic Sea as a part of the BALTEX project to examine the present state of the art concerning different precipitation estimates over that area. Several methods are used, with the focus on 1) interpolation of available synoptic stations; 2) a mesoscale analysis system including synoptic, automatic, and climate stations, as well as weather radar and an atmospheric model; and 3) measurements performed on ships. The investigated time scales are monthly and yearly and also some long-term considerations are discussed. The comparison shows that the differences between most of the estimates, when averaged over an extended period and a larger area, are in the order of 10-20%, which is in the same range as the correction of the synoptic gauge measurements due to wind and evaporation losses. In all data sets using gauge data it is important to include corrections for high winds. To improve the structure of precipitation over sea more focus is to be put on the use of radar data and combinations of radar data and other data. Interpolation methods that do not consider orographic effects must treat areas with large horizontal precipitation gradients with care. Due to the large variability in precipitation in time and space, it is important to use long time periods for climate estimates of precipitation
Ship measurements are a valuable contribution to precipitation information over sea, especially for seasonal and annual time scales.
North Atlantic Oscillation; a Climatic Indicator to Predict Hydropower Availability in Scandinavia
Authors: Uvo Cintia B. , Berndtsson Ronny 
Published: May 2018

Climate variability and climate change are of great concern to economists and energy producers as well as environmentalists as both affect the precipitation and temperature in many regions of the world. Among those affected by climate variability is the Scandinavian Peninsula. Particularly, its winter precipitation and temperature are affected by the variations of the so-called North Atlantic Oscillation (NAO).
The objective of this paper is to analyze the spatial distribution of the influence of NAO over Scandinavia. This analysis is a first step to establishing a predictive model, driven by a climatic indicator such as NAO, for the available water resources of different regions in Scandinavia. Such a tool would be valuable for predicting potential of hydropower production one or more seasons in advance.