Pollutant Spreading in a Small Stream: A Case Study in Mala Nitra Canal in Slovakia

• Published in: Environmental processes 2014-09, Vol.1 (3), p.265-276
• Main Authors: Velísková, Yvetta, Sokáč, Marek, Halaj, Peter, Koczka Bara, Márta, Dulovičová, Renáta, Schügerl, Radoslav
• Format: Article
• Language: English
• Subjects: Coefficients; Computer simulation; Contaminants; Dimensionless numbers; Discharge; Dispersion; Earth and Environmental Science; Earth Sciences; Environmental impact; Environmental Management; Environmental Science and Engineering; Evaluation; Exact solutions; Experiments; Mathematical models; Numerical models; Original Article; Parameter modification; Pollutants; Pollution dispersion; Pollution sources; Pollution transport; Rivers; Stream pollution; Streams; Surface water; Toxic substances; Waste Management/Waste Technology; Wastewater; Wastewater disposal; Water management; Water pollution; Water quality; Water Quality/Water Pollution
• ISSN: 2198-7491; 2198-7505
• DOI: 10.1007/s40710-014-0021-y

The Water Framework Directive requires as an obligatory goal to achieve and to keep “good water quality” status within the defined period (for Slovakia—up to the year 2015). For surface waters, the main criterion is the ecological and chemical status of the water. Mathematical and numerical modelling allows evaluating various situations of contaminants spreading in rivers (from everyday wastewater disposal through fatal accidents and discharges of the toxic substances) without immediate destructive impact to the environment. Determination of longitudinal and transverse dispersion coefficient values, as the main hydrodynamic characteristics of the dispersion, has the highest extent of uncertainty for hydrodynamic models simulating pollutant transport in streams. This paper deals with the determination of dispersion coefficients based on field tracer experiments performed in a small modified stream (basic hydrodynamic parameters during the experiments were: discharge Q  = 0.138–0.553 m 3 .s −1 , depth h  = 0.29–0.48 m, width B  = 5.2–5.9 m). During the experiments, various conditions and situations were taken into account, e.g., continuous and instantaneous pollution source, as well as various positions of pollution source along the river width, among others. Field measurements were evaluated using three different methods for dispersion coefficient determination: based on statistical evaluation, based on analytical solutions of advection–dispersion equation, and using numerical models. The dimensionless dispersion coefficients values were determined, which can be used for numerical simulation of pollutant transport in similar types of streams.