J. Hydrol. Hydromech., 62, 2014, 1, 43–54 DOI: 10.2478/johh-2014-0007 43 Analysis of efficiency of pollution reduction measures in rural basin using MIKE Basin model. Case study: Olšava River Basin Jana Kaiglová, Jakub Langhammer * Charles University in Prague, Faculty of Science, Albertov 6, 128 43, Prague, Czech Republic. * Corresponding author. E-mail: jakub.langhammer@natur.cuni.cz Abstract: This paper presents the results of testing the applicability of the MIKE Basin model for simulating the effi- ciency of scenarios for reducing water pollution. The model has been tested on the Olšava River Basin (520 km 2 ) which is a typical rural region with a heterogeneous mix of pollution sources with variable topography and land use. The study proved that the model can be calibrated successfully using even the limited amount of data typically available in rural ba- sins. The scenarios of pollution reduction were based on implementation and intensification of municipal wastewater treatment and conversion of arable land on fields under the risk of soil erosion to permanent grassland. The application of simulation results of these scenarios with proposed measures proved decreasing concentrations in downstream moni- toring stations. Due to the practical applicability of proposed measures, these could lead to fulfilment of the water pollu- tion limits required by the Czech and EU legislation. However, there are factors of uncertainty that are discussed that may delay or limit the effect of adopted measures in small rural basins. Keywords: Water quality; Modelling; Rural basins; MIKE Basin; Non-point pollution; Land use. INTRODUCTION The rural basins represent specific and frequent problems for water management and planning due to the difficulties in iden- tification and calculation of pollution coming from dispersed and non-point sources, a long-term perspective of change, and the frequent lack of systematic monitoring and relevant data. To evaluate information on the changes in water quality and to simulate the effect of potential measures for water pollution reduction, a number of mathematical models are available for use as versatile and easy-to-use tools for research and water management. The standard water quality models applied for the assessment of water quality in streams, e.g. QUAL2E/2K (Brown and Barnwell, 1987; Chapra et al., 2006), MIKE 11 (Havn et al., 1995) and HSPF (EPA, 2000), are usually based on a one-dimensional (1-D) conceptualization of stream hy- draulics and steady-state runoff (Borah and Bera, 2003; Højberg et al., 2007; Wang et al., 2006). The rapid development of GIS technology and the availabil- ity of detailed spatial data allowed the construction of compre- hensive modelling tools for simulation of hydrological process- es and contamination of the water environment, including the U.S. EPA Basins (EPA, 2001), MIKE Basin (DHI, 2008), WMS (Nelson et al., 2002) and SWAT (Arnold and Fohrer, 2005). The comprehensive models present techniques available to assess and complete the information on the pollution in space and time, and to assess the impact and efficiency of the pro- posed measures for abatement of the pollution (Borah and Bera, 2003). The modelling tools require data at the level of detail that is often unavailable in typical rural catchments of small and me- dium size, although the solution of problems with water pollu- tion in these basins is essential for fulfilment of objectives of water management legislation; namely the Water Framework Directive 2000/60/EC (hereinafter referred to as WfD, EC, 2000) and Nitrate Directive (EEC, 1991). This article presents the results of research that aims at iden- tifying the potential and limits of the MIKE Basin model for analysis and dealing with tasks related to the application of the requirements of the EU WfD (EC, 2000) in water management. The article points to the following objectives: 1. Analysis of the efficiency of point pollution reduction measures required by the current legislation in a rural basin by means of a complex model, 2. Calculation of the potential effect of measures for elimination of non-point pollution, designed with respect to their practical applicability, 3. Testing of the suitability of the MIKE Basin model for application in a small basin with limited sources of input data. The MIKE Basin model was used for simulating the impact of measures for water quality improvement in the Olšava River Basin. This model was chosen because of its potential for solv- ing complex issues on different basin scales (Jha and Gupta, 2003) and because of the acceptable qualitative and quantitative input data requirements. The MIKE Basin model is also being used by Czech water management authorities for modelling the impact of measures implemented in river basin management plans (RBMPs) prepared by water board authorities. The model was applied to a case study of the Olšava River Basin, at the border between the Czech Republic and Slovakia, representing a typical rural basin with a complex structure of pollution sources and burdened with long term problems with water pollution (Langhammer and Kliment, 2009). The study evaluated the potential and limits for the application of this modelling tool in finding strategies to improve the state of water quality in the Olšava River Basin. The indicators BOD 5 , COD, N-NH 4 , N-NO 3 and P total represent the basic parameters for water quality assessment and for environmental planning purposes. The simulation period is based on the same time horizon as is required in current water management legislation for setting up water management plans compliant with the EU WfD (EC, 2000).