Journal of International Scientific Publications: Ecology and Safety Volume 8, ISSN 1314-7234 (Online), Published at: http://www.scientific-publications.net MODELING OF CONTAMINANT DISPERSION IN STREAMS – 1D VERSUS 2D MODEL USE COMPARISON: CASE STUDY ON THE ONDAVA RIVER Peter Halaj 1 , Yvetta Velísková 2 , Marek Sokáč 3 , Viliam Bárek 1 , Jakub Fuska 1 1 Slovak University of Agriculture in Nitra, Trieda Andreja Hlinku 2, Nitra, Slovakia 2 Institute of Hydrology SAS, Račianska 75, Bratislava, Slovakia 3 Slovak University of Technology in Bratislava, Radlinského 11, Bratislava, Slovakia Abstract Article is focused on comparison of some aspects of 1D and 2D water quality model use for modeling of contaminant spreading in rivers. Properties of numerical models MODI and HEC-RAS were tested at 422 m long reach of the Ondava River. Results showed that HEC-RAS model can be used only for scenario or river reach along which the transverse pollution spreading can be complete. Better choice for this case study represents the model MODI that in 2D schematization shows detailed spatial structure of contaminant distribution in time as well as to specify the exact position of pollutant source outlet that effect the character of pollution cloud downstream transported. The results of simulations have proved that numerical models MODI as well as HEC-RAS model allow a reasonable support in decision making process connected to river water quality management. Key words: water quality modeling, HEC-RAS, MODI model, 1D and 2D water quality models INTRODUCTION The present legislation evaluating the quality of water bodies in Slovakia is based on implementation of the Water Framework Directive (2000/60/ES) (Torma & Fazekašová, 2007). Climate and hydrological changes, modification of physical conditions in streams affect, inter alia, transport phenomena including pollution propagation in stream channel (Babošová et al. 2006; Boltižiar, et al. 2012; Horák & Šiška 2008; Supuka & Halada 2011). The water quality predictions affect uncertainty in inputs related to the analyzed transport process (Igaz et al. 2008; Igaz, et al. 2010; Macura et al. 2012) Solution of processes connected to transport and mixing of water with substances transported downstream by the flowing waters has wide practical application, especially in the studies of wastewater spreading and mixing of waters of different quality below the confluence. Knowledge of the dispersion processes in flowing waters maybe useful for river modification, outlet design or river confluence design to mitigate the potential negative impacts on instream biota. Numerical simulation is one of useful, helpful and advantageous tools in water management, especially for transport pollution problems in surface water. Solute transport models try to simulate the solute concentration changes in downstream transport with flowing waters. Use of numerical models provides possibility to simulate the effects of different scenarios of water quality problems, to optimize the design of water quality improvement measures or to assess the parameters value with limited information for the precise determination. When solving problems relating to water quality in streams its importance is even greater when considering the impact of adverse effects on the environment. Use of numerical models provides possibility to simulate the effects of different scenarios of water quality problems, to optimize the design of water quality improvement measures or to assess the parameters value with limited information for the precise determination. MATERIAL AND METHODS For analysis of pollution wave propagation from outfall in headwater reach of the Ondava River were used two- dimensional dispersion model MODI and one-dimensional model HEC-Ras. The MODI is a numerical model based on the advection-diffusion equation, which can simulate the spread of contamination in prismatic channel for steady-state flow conditions (Veliskova & Sokáč, 2012). MODI model was developed by researches of the Institute of Hydrology SAS Bratislava (Velísková & Kohutiar) in 1995. The model uses a concept of streamtubes. This concept is based on a coordinate system which divides the flow across the channel width in stream-tubes of unequal width, but with the same flow rate (Yotsukuru & Sayre, 1976). The simulation of non-conservative transport in longer stream reaches may be carried out by taking into account the self-purification processes. The discharge of pollution source outlet may be given as a steady or unsteady 393