LONGITUDINAL DISPERSION COEFFICIENT EVALUATION METHODOLOGY BASED ON RESULTS OF FIELD MEASUREMENTS

References: 13th SGEM GeoConference on Water Resources. Forest, Marine And Ocean Ecosystems, www.sgem.org, SGEM2013 Conference Proceedings, ISBN 978-619-7105-02-5 / ISSN 1314-2704, June 16-22, 2013, 205 - 212 pp

ABSTRACT

The EU Water Framework Directive requires as an obligatory goal to achieve and to keep the “good water quality” status within the defined period (for SK is this period set up to the year 2015). For the surface water will be the main criterion the rate of the ecological and chemical quality. In connection with the adoption of the measures for improvement of the surface water quality, the numerical simulation models are very useful tools, which are able to simulate the consequences of the adopted measures, i.e. their suitability, efficiency, eventually to show the inefficiency or unsuitability of the adopted measures.
This paper presents a part of preliminary results of research project focused on the quantification of input data influence on correctness of outputs of dispersion simulation models for surface water. The most important parameters of this phenomenon in water streams are longitudinal and transverse dispersion coefficients. Determining of their values is still connected with high degree of uncertainty.
Paper deals with various approaches to determination of longitudinal dispersion coefficient and with analysis of results. Determination of longitudinal dispersion phenomenon dependencies on principal hydraulic parameters of streams is studied, too. The field measurements, sampling and subsequent modeling were performed on various types of stream with free surface: in relatively long and straight channel section with prismatic flow bed and with relatively constant roughness of streambed, as well as in natural rivers with more irregularities and higher velocities. Consecutively the longitudinal dispersion coefficient in a prismatic channel with various direction changes was determined. Field measurements were evaluated using three various methods for dispersion coefficients determination: methods based on statistic dispersion evaluation, based on analytical solutions and methods using numeric models.

Keywords: longitudinal dispersion coefficient, field measurement, simulation of dispersion