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  • Articles  (9)
  • Articles: DFG German National Licenses  (9)
  • Hydrology  (5)
  • mathematical model  (4)
  • Springer  (9)
  • International Union of Crystallography (IUCr)
  • 1990-1994  (9)
  • Architecture, Civil Engineering, Surveying  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Simulation of water and nitrogen dynamics in soils during wastewater applications by using a finite-element model (1993)
    Springer
    Water resources management 7 (1993), S. 237-251 
    Details
    ISSN: 1573-1650
    Keywords: Land treatment ; water flow ; nitrogen transport ; mathematical model ; finite elements method ; unsaturated-saturated conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A mathematical model was developed to simulate water movement, mass transport, and nitrogen transformations in soils during wastewater applications. The model is one-dimensional and based on the Galerkin finite-element method. The submodel of mass transport of nitrogen incorporates the convection-dispersion processes of ammonium and nitrate nitrogen, nitrification, denitrification, ammonium exchange and uptake of ammonium and nitrate ions. The accuracy and validity of the proposed model was examined by comparison with an explicit-implicit finite-difference model results. The model was used for simulation of water and nitrogen dynamics during wastewater application in homogeneous and multi-layered soils under different N concentration, rate, duration and scheduling of application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01675306
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  • 2
    Electronic Resource
    Electronic Resource
    Statistical validation of GCM-simulated climates for the U.S. Great Lakes and the C.I.S. Emba and Ural River basins (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 69-80 
    Details
    ISSN: 1436-3259
    Keywords: Hydrology ; global circulation models ; statistics ; climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Many researchers use outputs from large-scale global circulation models of the atmosphere to assess hydrological and other impacts associated with climate change. However, these models cannot capture all climate variations since the physical processes are imperfectly understood and are poorly represented at smaller regional scales. This paper statistically compares model outputs from the global circulation model of the Geophysical Fluid Dynamics Laboratory to historical data for the United States' Laurentian Great Lakes and for the Emba and Ural River basins in the Commonwealth of Independent States (C.I.S.). We use maximum entropy spectral analysis to compare model and data time series, allowing us to both assess statistical predictabilities and to describe the time series in both time and frequency domains. This comparison initiates assessments of the model's representation of the real world and suggests areas of model improvement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581676
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  • 3
    Electronic Resource
    Electronic Resource
    A spacetime discontinuous Galerkin method for the two-dimensional unsteady convection-dispersion problems (1992)
    Springer
    Water resources management 6 (1992), S. 35-45 
    Details
    ISSN: 1573-1650
    Keywords: Artificial diffusion ; convection-dispersion ; Courant number ; discontinuous Galerkin method ; finite element computational scheme ; mathematical model ; Péclet number ; Petrov-Galerkin ; water contamination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The unsteady two-dimensional convection-diffusion (CD) equation, which is the governing equation of the unsteady two-dimensional convection-dispersion problem, as the water contamination problems, has a mixed hyperbolic-parabolic character. When the equation has a strong mixed hyperbolic character, the exact solution is nonsmooth. In this case, the conventional numerical methods give approximate solutions which either oscillate or smear out the sharp front of the exact solution. The spacetime discontinuous Galerkin method (STDGM) is an extention of the space discontinuous Galerkin method (SDGM), applying the discontinuity in the time direction, as well as in space. Both these methods are respective modifications of the standard Galerkin finite element method (SGM). In this paper, the STDGM is applied to solve the CD equation, when the Péclet number has extremely high values, which means a strong mixed hyperbolic character. With this method, three artificial diffusion terms are introduced by modifying the test functions of the finite element method. These functions include the discontinuity int, x andy axis. The results obtained from the analytical solution of the problem are used for testing the numerical solution, applying both the space-discontinuous Galerkin method (SDGM) and the STDGM and are presented in diagrams, from which useful observations, comparisons and conclusions can be drawn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872186
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  • 4
    Electronic Resource
    Electronic Resource
    Appraisal and optimization of agricultural water use in large irrigation schemes: I. Theory (1992)
    Springer
    Water resources management 6 (1992), S. 185-199 
    Details
    ISSN: 1573-1650
    Keywords: Irrigation ; mathematical model ; path efficiency ; percolation ; water flow ; water extraction ; water supply
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A new approach on the functioning of an irrigation scheme has been presented. A mathematical representation of the irrigation system based on measured system properties, such as losses due to percolation and to poor management, in only a part of the system is used. This mathematical representation is termed an equivalent irrigation network. The merit of this approach is that it reduces the number of required streamflow measurements. When water amounts are measured for a number of paths in the irrigation network, so-called path efficiencies are obtained. The path efficiency is a measure of the amount of water lost along the way. The numerical model that simulates the operation of the irrigation system is based on the path efficiencies. This simulation model in turn is used to calculate different objective functions, corresponding with different optimization goals, like uniform water distribution, minimum groundwater extraction, minimum cost of water supply. This paper gives the theoretical background of the approach. The application to an actual irrigation scheme will be discussed in a second paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872355
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  • 5
    Electronic Resource
    Electronic Resource
    Observed advantage for negative binomial over Poisson distribution in partial duration series (1991)
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 135-146 
    Details
    ISSN: 1436-3259
    Keywords: Hydrology ; runoff ; partial duration series ; negative binomial distribution ; Poisson distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The goodness of fit of the negative binomial and the Poisson distributions to partial duration series of runoff events is tested. The data have been recorded by eight hydrometric stations located on ephemeral rivers in Isreal. For each station, a number of threshold discharges are considered, by that series of nested subsamples are formed. Owing to size limitations, a Chi-square test is conducted on samples associated with low to moderate threshold discharges. Positive results, at a 5% significance level, are obtained in 30 out of the 53 tests of the Poisson distribution, and in 22 out of the 28 tests of the negative binomial distribution. The fit of the Poisson distribution to samples of conventionally recommended sizes (of 2 to 3 events per year) is found positive for five rivers and negative for the three other rivers The fit of the negative binomial distribution to these samples is found positive for six rivers, inconclusive for one river and short of data for the eighth river. Mixed results are obtained as the threshold level is raised. Therefore, no direct extrapolation is possible to samples associated with high thresholds. An indirect extrapolation is drawn through a comparison of the actual properties of the samples with those expected under a perfect fit of the distribution functions. Ranges of such properties are defined with respect to the properties of the tested samples and to the test results. The actual properties of nine of the eleven samples associated with high thresholds (i.e. mean number of events 〈-0.1year −1) are found within these ranges. This provides a hint for a probable good fit of either distribution, and particularly the negative binomial, to the occurrence frequency of high events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543055
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  • 6
    Electronic Resource
    Electronic Resource
    On some apparent paradoxes in water spreading, hydrology and seepage (1991)
    Springer
    Water resources management 4 (1991), S. 273-281 
    Details
    ISSN: 1573-1650
    Keywords: Hydrology ; infiltration ; water spreading ; drainage ; cavitation ; anisotropy ; paradoxes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In water spreading and underground hydrology, one should beware of pitfalls. This is illustrated by several examples of vertical downflow and upflow. Drainage by overcharging: When a fine-grained soil overlies a coarse-grained soil, a certain amount of water can be suspended in the interzone. Adding water may cause excessive drainage. Cavitation in soils: When water flows from an upper less pervious layer to a more pervious layer, the pressure head in the interzone may become negative, the gases dissolved are released in the form of bubbles which render the soil temporarily impervious. At the initial instant of seepage of water from a pond into a dry soil, inertial forces and kinetic energy cannot be neglected. At the interface of two anisotropic media, the angle of refraction of a streamline depends on the tangential hydraulic conductivity only, whereas that of a gradient line depends on the normal component only. Impossibility of steady-state evaporation from a deep water table: It is shown that the water concentration may become negative, which is physically impossible. Two modes of downflow: In insaturated downflow there exists a critical water concentration c such that the corresponding hydraulic conductivity K(c) is equal to the descending specific flux. The moisture distribution is radically different in the subcritical and supercritical zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00430341
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  • 7
    Electronic Resource
    Electronic Resource
    A space discontinuous Galerkin method for the one-dimensional unsteady convection-diffusion equation (1990)
    Springer
    Water resources management 4 (1990), S. 175-185 
    Details
    ISSN: 1573-1650
    Keywords: Artificial diffusion ; convection-diffusion ; mathematical model ; Peclet number ; Petrov-Galerkin ; water contamination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A space discontinuous Galerkin method, which is called streamline diffusion method (SDM), is applied to compute the convection-diffusion equation, when the solution of a problem is not globally smooth, but varies rapidly in certain narrow regions. This method is a Petrov-Galerkin modification of the standard Galerkin (SGM) finite element method. To eliminate the oscillations, which are produced when the so far conventional numerical methods are applied for problems where the Peclet numbers are Pe〉1, an artificial diffusion term along the streamline direction is introduced by modifying the test functions of the finite element method. The results, obtained from the analytical solution of the problem, are used for testing the numerical solution, applying the SGM and the SDM methods, with low and high Peclet numbers and are presented in diagrams from which useful observations, comparisons and conclusions can be drawn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431142
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  • 8
    Electronic Resource
    Electronic Resource
    Symbiosis between systems engineering and hydrology (1990)
    Springer
    Water resources management 4 (1990), S. 161-173 
    Details
    ISSN: 1573-1650
    Keywords: Hydrology ; water management ; systems science ; control ; systems engineering ; systems scientists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The system concepts of importance to hydrological sciences are reviewed. The epochs of the development of systems sciences are discussed and their links with hydrological and water resources research are illustrated. Potentials and limitations of the system approach are discussed and the perspectives of further applications are sketched.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431141
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  • 9
    Electronic Resource
    Electronic Resource
    A new ‘momentum method’ for the quantitative and qualitative evaluation of Polish rivers (1990)
    Springer
    Water resources management 4 (1990), S. 219-227 
    Details
    ISSN: 1573-1650
    Keywords: Hydrology ; water quality ; momentum equation ; Polish rivers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract There is a tendency in water management to identify the resources of surface waters with river discharge expressed by the intensity of the flow. However, such an evaluation is insufficient because of the difficulties in the water-economic balancing of the basin resources, since it does not take into account the volume of water contained in the river channel. With heavy pollution of the water flowing in the river channel, this fact may have a considerable influence on the representativity of the balance. The above reasons have become a basis for the introduction of a new measure for the evaluation of pollution resources of flowing water. The quantity of water in motion in a river channel is expressed by the momentum equation. Evaluation of water resources has been carried out for 83 rivers in the Vistula Basin and 52 rivers in the Odra Basin by means of the stream momentum method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431145
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