Pollution Spread Analysis In The Malá Nitra River By Using Of 1-D Model

The Water Framework Directive (WFD) is a key initiative aimed at improving water quality throughout the EU. The development of the computer technologies enables us to solve the ecological problems in water management practice very efficiently. The mathematical and numerical modelling allows evaluating various situations of contaminants spread in rivers (from everyday wastewater disposal through the fatal discharges of toxic substances) without immediate destructive impact on the environment. The paper deals with 1-dimensional numerical model HEC-RAS and its response on various values of dispersion coefficient. This parameter is one of the most important input data for simulation of pollution spread in streams. There were performed tracer experiments in the Malá Nitra River and results of these measurements are compared with results of numerical simulations. The values of the longitudinal dispersion coefficient were estimated from this comparison. The range of mean values of this coefficient determined on the base of numerical model application was 0.05 – 0.13 m² s⁻¹, for the other flow condition it was 0.07 – 2.5 m² s⁻¹ or 0.28 – 0.6 m² s⁻¹. The next task was carrying out the model sensitivity analysis, which means to evaluate input data influences, especially longitudinal dispersion coefficient, on outputs computed by 1-dimensional simulation model HEC-RAS. According to the results it can be said that the model HEC-RAS responds to longitudinal dispersion coefficient value changes adequately, suitably and proportionately. The application of the model HEC-RAS demonstrated the eligibility for simulation of pollution spread in streams, which means that it is a suitable tool allowing a reasonable support in decision making process connected to river water quality management.