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

Abstract

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.

Landslide-Induced Mass Transport of Radionuclides along Transboundary Mailuu-Suu River Networks in Central Asia

“…The longitudinal dispersion of solute contamination is commonly difficult to determine because it depends on various variables and their nonlinear inter-relationships [52]. Based on the measured geometric values, we found a negative correlation between the dispersion coefficient and stream velocity.…”

“…The transport simulation was based on the ADE model in HEC-RAS, which describes the mass conservation of substances transported in the direction of the flow [39]. The dispersion of suspended matter is mathematically described by Fick's law, where the dispersion coefficient includes the combined effects of molecular diffusion, turbulent mixing, and mixing due to transverse and vertical shear associated with cross-stream velocity differences [12,52].…”

“…A number of riverine parameters have effects on the estimation of the dispersion coefficient along the longitudinal gradient of river networks. The essential ones included viscosity, density, water depth, channel width, shear velocity, mean velocity, bed slope, horizontal stream curvature, bed shape factor, and bed roughness [38,52]. The suggested equations (i.e., Equation (2) and Equation (3)) for computing the dispersion coefficient from the HEC-RAS user manual was used in this study [37] = 0.011…”

Longitudinal Dispersion Prediction of River Balogun Using Constant Distance and Time Approach at Different Sampling Time Intervals

“…However, when this is hampered, their existence will be under threat. With the EU bearing this in mind, a Water Framework Directive (WFD) in 2000 was designed to help chart this course [1], [2]. Even at that, it is herculean to find some of the rivers within the EU member states void of some form of effluent discharge.…”