bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Applications of a Runoff Model for Snowcovered and Glacierized Basins
Authors: Gottlieb Lars 
Published: May 2018

A conceptual model has been developed for the prediction of runoff on a daily basis from snowcovered and glacierized basins. The basin is divided into an icefree area and an icecovered area, which are treated separately by the model in an attempt to account for the highly different physical conditions prevailing within these two types of areas. The heat exchange between the atmosphere and the snow- or icecover, which essentially controls the melt production, is calculated either by means of a modified degree-day approach or – if the necessary data are available – by means of the complete energy balance equation. The performance of the model has been tested on a glacierized basin in Western Canada – The Peyto Glacier Basin – from which eight years af basic meteorological observations exist for the melt period in addition to continuous discharge measurements.
Further, the model has been applied to a glacierized basin in Johan Dahl Land, Southern Greenland, which is of interest in relation to hydro power development. The purpose of this study has been to extend the existing 4 years series of discharge measurements on basis of long term meteorological observations from a station located appr. 17 km from the outlet of the basin.
The results of the two case studies are presented and discussed.
Exceptional Groundwater Level Fluctuations at the Dutch Island of Schiermonnikoog
Authors: de Zanger F. A. P. 
Published: May 2018

During a hydrological-meteorological investigation at a former beachplain at the Dutch island of Schiermonnikoog, groundwater fluctuations were recorded. Except for daily changes of the groundwater level there appeared to be exceptionally high fluctuations during rainfall. This phenomenon can be explained by the so-called »lisse-effect«.
This implies that the phreatic level can rise rapidly due to an increased pressure of the soilair above the capillary fringe. The increase of the pressure is caused here by the capillary infiltration of rainwater in the soil
At Schiermonnikoog it became obvious that the depth of infiltration and the extent of groundwater rise were determined by the thickness of a semipervious layer at the surface with strong capillary tension.
Sodium Mobility in a Mini-Catchment Studied with Radioactive Tracers and Artificial Precipitation
Authors: Christophersen N. , Seip H.M. , Qvenild C. , Tollan O. 
Published: May 2018

Seasalts in the precipitation may lead to a short-term acidification of the runoff from natural catchments due to ion-exchange reactions. It was decided to investigate this effect in the Storgama area which has acidic streamwater and lies in Telemark county, southern Norway. The mobility of 24Na as compared to that of tritiated water (HTO) was studied in a natural mini-catchment (98 m2, 61% barren granitic bedrock) using artificial precipitation with an intensity of about 5 mmh−1. The tracers were delivered as a pulse, and after 6 days (4 days with watering) an estimated 84% of the HTO reaching the plot was recovered in the outlets compared to 45% for 24Na. Sodium is therefore fairly mobile in the mini-catchment, but the results show that the positively charged sodium ions are delayed compared to the water movement as traced by HTO.
From the observed sodium mobility and the [Na] values commonly occurring in natural precipitation in this area (average 15 μeql−1), it is estimated that the short-term acidification of the runoff due to seasalts is of minor importance in the mini-catcment which typically has [H+] ≈ 50 μeql−1 in runoff. This is probably also the case for the Storgama area as a whole.
Acidification of Groundwater in Norway
Authors: Henriksen A. , Kirkhusmo L. A. 
Published: May 2018

The chemistry of ground- and surface-water in areas of similar geologic settings are compared by plotting the equivalent concentrations of each component in an XY-diagram. The deviations of each chemical component from the line through origin and the plot of the two ionic sums (line of proportional composition) give information about the differences in composition of the two types of water.
If we assume that the geologic conditions of the ground- and surface-water are similar when the plots of calcium and magnesium will fall close to the ionic sum line, then we find that the alkalinity is relatively higher and the sulphate concentration is relatively lower in groundwater than in surface-water. These observations indicate that in areas influenced by acid precipitation the groundwater is acidified less than the surface water.
The groundwater stations studied so far show a regional tendency to lower pH-values in areas where regional lake surveys show low pH in surface waters, these areas include southernmost Norway and parts of eastern Norway.
Profiles of Nitrogen Species in a Sand-Silt Aquifer at Haslemoen, Solør, South Norway
Authors: Englund J.-O. , Haldorsen S. 
Published: May 2018

Chemical profiles of water in the vadose zone and in the upper part of the groundwater from a water-table sand-silt aquifer at Haslemoen, South Norway, have been studied. Filter tips attached to steel pipes (BAT monitoring system) have been installed to different depths at two localities. The system makes it possible to measure pore pressures and hydraulic conductivities and to take samples under controlled conditions both above and below the groundwater level. One locality is characterized by forest, groundwater level at about 7 m below surface, and filter tips down to 13.2 m. Agricultural land surrounds the field installations at the other locality, the groundwater level is here about 4.5 m below surface, and filter tips are down to 10.4 m.
The chemical data demonstrate a) Higher concentrations of both total nitrogen and nitrate below agricultural land b) Decreasing concentrations downwards of both total nitrogen and nitrate in both profiles c) Iron and/or organic carbon seems to take part in the reduction of nitrate, probably to free nitrogen.
Stochastic Modelling of a Contaminated Aquifer
Authors: Van Rooy Dirk 
Published: May 2018

A stochastic solute transport model is applied to a groundwater contamination case. The contamination is caused by leachate from an unprotected landfill situated in a highly-permeable unconfined aquifer.
The stochastic model combines the geostatistical techniques of semivariogram analysis and kriging with a numerical solute transport model. A Monte Carlo approach that utilizes the turning bands technique to genereate transmissivity fields is used. Here some preliminary results of the unconditional stochastic simulations are presented.
The contaminant plume is characterized by expected concentrations of chloride and standard deviations.
Field Investigation of the Thermal Bar in Lake Ladoga, Spring 1991
Authors: Malm Joakim , Grahn Lennart , Mironov Dmitry , Terzhevik Arkady 
Published: May 2018

The thermal bar in Lake Ladoga was studied during one week in May 1991. Temperature and current velocity distributions were measured. The movement of the thermal bar and the horizontal heat transport were examined.
The temperature off-shore the thermal bar was found to be constant within a vertical. The velocity distributions were complex and dependent on wind conditions. Calculations of changes in heat content showed that there was a horizontal heat transport from the near-shore warm zone towards the thermal bar. The observed off-shore progression of the thermal bar was compared with analytically computed progression rates. The progression rate is underestimated if it is assumed that surface heating and vertical mixing are the only mechanisms contributing to the thermal bar progression. Better agreement is obtained if mixing of warm and cold water near the thermal bar zone is considered.
Prediction of Log-Transmissivity
Authors: Christensen Steen 
Published: May 2018

The log-transmissivity may in many cases be predicted from the log-transformed specific capacity of wells by applying a linear statistical model. The coefficients of the linear equation can be estimated by the least-square method. It is shown that if the estimated slope of the line differs from unity then it may indicate that the specific capacity is correlated with the well efficiency.
The above prediction method is applied to case studies of aquifers in three different formations: the prediction should not be used for a homogeneous fluvioglacial formation because the variance of the well efficiency dominates the variance of the transmissivity; the prediction is fair for a heterogeneous fluvioglacial formation; and the prediction is poor for a homogeneous limnic formation. In the study of the first formation a correlation between specific capacity and well efficiency can be identified directly from the slope of the regression line.
If the predictor values are taken from the drillers log then the standard error of prediction in all the cases is 0.35. This seems to be unacceptable in most practical applications. However, if one needs to predict the mean of a domain and the domain contains a number of observations of the predictor, then the averaging will reduce the prediction error. The averaging procedure ought to take the covariance structure of the variables into consideration.
Spring Circulation Associated with the Thermal Bar in Large Temperate Lakes
Authors: Malm Joakim 
Published: May 2018

The overall circulation pattern in spring is rather specific as density-induced currents may be of significance. The density-driven circulation perpendicular to the shore can be described as consisting of two circulation cells, with a zone of convergence, referred to as thermal bar, in between. The thermal bar, which coincides with the 4°C isotherm (the temperature of maximum density), inhibits horizontal water exchange, implying its practical importance. In this paper, a hydrodynamic numerical model is used to study the relative influence of wind- and density-driven currents in a large temperate lake during spring.
The study shows that the general density-driven circulation is strongly dependent on the bottom topography, with a more pronounced circulation and considerable descending motions in the thermal bar zone in lakes with steep sloping bottoms. In shallow lakes, the wind-driven circulation dominates, and the effect of density-induced currents is marginal, except at locations with a drastic change in bottom depth.
A Simple Monthly Runoff Model for Snow Dominated Catchments in Western Himalayas
Authors: Rao S. V. N. , Ramasastri K. S. , Singh R. N. P. 
Published: May 2018

The rivers originating from middle and greater Himalayas have a significant part of their catchments under permanent snow cover and glaciers. Modeling runoff becomes difficult with almost no data from these parts. Even in the seasonal snow covered zones, the network is generally inadequate. However precipitation characteristics show repetitiveness and snowline movement elevation wise by and large occurs the same pattern each year. The snowline movement is distinct on a monthly basis and the location of permanent snowline is also more or less constant at about 4,500 m.
A simple monthly snowmelt runoff model with relatively few parameters is proposed to take advantage of above mentioned characteristics, using the degree day method. The model uses monthly rain, snow (snow water equivalent), mean air temperature and snowline elevation as primary inputs. Model conceptualisation has been made in view of the data constraints. All parameters are estimated through few trial simulations, except the storage coefficient, which is optimised using Rosenbrock technique.
The model was applied on two sub-catchments of Chenab basin (of Indus river system) to evaluate the model capability. The results are encouraging. There is further scope for model improvement, generalisation and for application to other catchments in the Western Himalayas.
Temperature and Salt Content Regimes in Three Shallow Ice-Covered lakes
Authors: Malm J. , Terzhevik A. , Bengtsson L. , Boyarinov P. , Glinsky A. , Palshin N. , Petrov M. 
Published: May 2018

A field study was carried out in three small shallow ice-covered lakes to study heat and mass fluxes and their spatial and temporal variability. During the main part of the winter, the heat flux at the ice-water interface, being of the order 0.5-1 W m−2, was dominated by conduction from water to ice and did not show any significant variations in time or space. The heat flux from sediments to water was the main source for the lake water heating during early and mid-winter, being depth-dependent and 1-4.5 W m−2 in early winter, and 0.5-3 W m−2 in late winter. A heat transport from shallow regions to deep parts was shown to occur during the winter, being of the same order as the vertical fluxes, and should thus be accounted for in any attempt to predict the temperature evolution in an ice covered lake.
The salt flux from sediments was found to be of the order 1-10 × 10−10 kg m−2 s-l. A comparison of this flux with salt content changes indicates that the former is of the same order as the horizontal salt flux which is directed from shallow regions to the deeper parts of a lake during winter.
Slushflow Hazard and Mitigation in Vesturbyggd, Northwest Iceland
Authors: Tómasson Gunnar Gudni , Hestnes Erik 
Published: May 2018

Slushflows – flowing mixtures of water and snow – threaten several residential areas within Vesturbyggð, a municipality of 1250 people located in the Vestfirdir peninsula in Northwest Iceland. An overview of the problem is given and particular attention is drawn to the catastrophic events of January 22nd 1983 in Patreksfjörður, when two slushflows damaged or destroyed 20 houses, killing four of the twelve people caught in the them. As the runout zones of the slushflows are densely populated the local authority requested an appraisal study for slushflow defences. For the main hazard zone below Geirseyrargil the work included an evaluation of potential starting zones, hazard areas, mitigative measures and cost estimates compared with the value of the involved properties.
Slushflow activity in Vesturbyggð and other parts of Iceland is associated with cyclonic activity during winter as well as spring break-up periods. Most commonly, slushflows are released in drainage channels and streams, but they may also start from inclined depressions. Snow-embanked, water-saturated snowfields are other potential starting zones. Whether a snowpack will reach a critical stability during rain and snowmelt depends on the complex interaction between geomorphic factors, snowpack properties and the relative rate of formation and discharge of free water in the snowpack in potential starting zones. By analysis of meteorological records from the autumn of 1982 and January of 1983 the snowpack development prior to the events and stability of the snowpack at the start of the critical weather period in January 1983 are estimated.
Rainfall Runoff Modelling Based on Genetic Programming
Authors: Babovic Vladan , Keijzer Maarten 
Published: May 2018

The runoff formation process is believed to be highly non-linear, time varying, spatially distributed, and not easily described by simple models. Considerable time and effort has been directed to model this process, and many hydrologic models have been built specifically for this purpose. All of them, however, require significant amounts of data for their respective calibration and validation. Using physical models raises issues of collecting the appropriate data with sufficient accuracy. In most cases it is difficult to collect all the data necessary for such a model.
By using data driven models such as genetic programming (GP), one can attempt to model runoff on the basis of available hydrometeorological data. This work addresses use of genetic programming for creating rainfall-runoff models on the basis of data alone, as well as in combination with conceptual models (i.e taking advantage of knowledge about the problem domain).
Dynamics of River Flow Regimes Viewed through Attractors
Authors: Krasovskaia Irina , Gottschalk Lars , Leblois Etienne , Sauquet Erik 
Published: May 2018

Analysing complicated systems we must never forget that the extraordinary increase in the rate of progress in our understanding can tell us nothing about the state of our knowledge.
H.Metzger (1994)
The hydrological system is extremely complex. To get insight into its behaviour and possible future states it is important to assess not only its individual components but also consider their interaction. Studying the hydrological system in its context allows focusing on the inherent patterns of its behaviour and search for external rules of its functioning. Changing climate can alter the seasonality of river flow, increasing the frequency of some patterns and decreasing that of the other, which can be adequately described in probabilistic terms. Dimensionality reduction facilitates to discern the patterns present in high dimensional systems. The approach suggested herein allows studying the dynamics of river flow seasonality patterns in the context of the present hydrological system in terms of the probability density functions of the weight coefficients in the reduced phase space, using Principal Components for dimensionality reduction. The approach is presented on the example of a large sample of monthly runoff series for Scandinavia and France, which gives a possibility to identify some common features in the dynamics of seasonality of river flow across a vast region of Europe.
Simulation of a Biogeochemical Model in Different Lakes
Authors: Pers Bodil Charlotta , Persson Irina 
Published: May 2018

Eutrophication, caused by nutrients leached from soil and emitted from point sources, is a well-known problem in many Swedish lakes. There are several countermeasures that can be used to reduce eutrophication. A model that can simulate the biogeochemical response to different management scenarios may help with nutrient reducing strategies. Results from applications with such a model to different types of lakes are presented in this paper.
The most important variables simulated by the model are dissolved nutrient concentrations (nitrogen and phosphorus) and phytoplankton. Other variables include nitrogen fixating cyanobacteria, sediments, and zooplankton. In total, 14 state variables are simulated. Nutrients are supplied through tributaries, and the temperature and vertical mixing forced by meteorological input.
The model is able to simulate effects of changing nutrients and plankton dynamics. It is promising as an instrument for evaluating various measures to improve water quality in lakes. However, for the lakes the model has been applied to, the model has been calibrated to available observations. Non-monitored lakes could also be interesting to simulate, therefore the parameters of the model set-ups are discussed in this paper.
Flow categorization model for improving forecasting
Authors: Sivapragasam C. , Liong Shie-Yui 
Published: May 2018

Prediction of high magnitude flows is of interest in many hydrological applications such as operation of flood control reservoirs, flood forecasting and gated spillways. Of the various types of existing streamflow prediction approaches, data driven models (such as ANN) are increasingly being preferred over the traditional conceptual models due to their simplicity, fast speed and ease of use. For models that consider only historical streamflow data, an attempt has been made to design a robust model over a wide range of streamflow magnitudes. The model inputs are the immediate past streamflow data which generally do not predict the typically high flows well, particularly for large lead times.
In this study, the flow range is divided into three regions (low, medium and high flow regions) and the attributes are decided based on the underlying hydrological process of the flow region. A flow forecasting model is applied for each flow region, using only the historical streamflow data as input. The proposed approach is implemented in Tryggevælde Catchment (Denmark) for 1- and 3-lead days, using the Support Vector Machine (SVM), which yields promising results, particularly for high flows in a 3-lead day model.
Modelling of drinking water treatment processes within the Stimela environment
Authors: van der Helm A.W.C. , Rietveld L.C. 
Published: May 2018

Drinking water production plants (in The Netherlands) are normally controlled by effluent quality. When the effluent quality does not meet the guidelines, the treatment process is manipulated. This is mainly done using the experience of the operators. Water quality models can be used to support the operators' task by off-line process evaluation and model predictive control (MPC).
Stimela is a modelling environment that is developed by DHV Water BV and the Delft University of Technology. It is especially designed for water quality modelling. An example of off-line use of Stimela for operation and design is given by a model of a counter-current packed tower aerator.
In the near future Stimela will be used for MPC. Therefore DHV Water BV and the Delft University of Technology are starting a project with water companies in which MPC with Stimela will be applied. In this project internet technology will be used to access water quality data from online measurements and form the model calculations. The data can be used by operators when they are at other locations, by drinking water technologists at the office to analyse specific problems, and by the management for weekly, monthly and yearly reports. In this way all the data are available for everyone in the organisation, from the operator to the managing director.
Spores of sulphite-reducing clostridia (SSRC) as surrogate for verification of the inactivation capacity of full-scale ozonation for Cryptosporidium
Authors: Hijnen W.A.M. , van der Veer A.J. , van Beveren J. , Medema G.J. 
Published: May 2018

The inactivation of C. parvum and spores of Cl. perfringens by ozone treatment in natural water in a lab-scale continuous-flow system was compared. In addition the inactivation of the natural occurring spores of sulphite-reducing clostridia (SSRC) in this water was monitored in one of the lab-scale systems as well as in a full-scale ozonation process. The survival ratio of C. parvum oocysts was determined using the CD-1 neonatal mouse infectivity test and for Cl. perfringens and SSRC the survival ratio was assessed with the standard anaerobic colony count on the iron-sulphite medium.
The results of the lab-scale experiments revealed an inactivation rate constant k (Chick-Watson modelling) at 10°C for C. parvum of 0.14 (SD=0.014; P&lt;0.001) and for Cl. perfringens of 0.25 (SD=0.01; P&lt;0.001). Moreover, first results of monitoring the SSRC inactivation in full-scale ozonation processes indicated that the inactivation rate constant for these wild strains was in the same order of magnitude as determined for Cl. perfringens. Further research is needed to compare inactivation ozone kinetics for Cl. perfringens D10 and SSRC at different temperatures and in other natural waters. Results of additional lab-scale experiments with Cl. perfringens strain D10 indicated that the CT of the gas-feed chamber should be incorporated in the design of a full-scale ozonation. Moreover, setting theCT with the contact time was not as effective for the inactivation capacity as setting the CT with the ozone dosage.