Assessment of Water Quality Status for the Selangor River in Malaysia Mohamad Ali Fulazzaky & Teng Wee Seong & Mohd Idrus Mohd Masirin Received: 30 November 2008 / Accepted: 16 March 2009 / Published online: 1 April 2009 # Springer Science + Business Media B.V. 2009 Abstract Water quality degradation in the Selangor River will still be present in the years to come since pollutant loads from poultry farms, municipal waste- waters, and industrial wastewaters are not envisaged to be handled effectively. This will be facing the problems of water quality status to use for multiple purposes and to provide its aquatic environment continuously. The water quality evaluation system is used to assess the water quality condition in the river. This system distinguishes two categories of water condition i.e., the water quality index and water quality aptitude. The assessment of water quality for the Selangor River from nine stations along the main stream, which concludes that water has been highly polluted (index 5) immediately downstream of station 02 Selangor River before confluence with Kubu River due to high concentration of microorganisms and immediately downstream of station 06 Selangor River before confluence with Batang Kali River due to high concentrations of microorganisms and suspended particles, was verified. Mineral micropollutants were found to gradually pollute the stream water, ranging from the unpolluted water (index 1) in the upstream to the bad quality (index 4) in the downstream area. Keywords Water quality evaluation system . Water quality index . Selangor River 1 Introduction Water resources management entails the development of appropriate quantities of water with an adequate quality. The tendency of water demands in Malaysia was estimated to increase from 9,543 m 3 /day in 1995 to 15,285 m 3 /day in 2010, or the increase of 60% during 15 years, to 20,338 m 3 /day in 2020, or 113% during 25 years (DOE 2003). There is a need to control and maintain the quality of raw water in the river to ensure the safe quality of available water because the deterioration of water quality reduces the usability of the resources for multistakeholders (Fulazzaky 2005). The quality of surface water has become a critical issue in many countries, especially due to the concern that freshwater will be a scarce resource in the future so a water quality monitoring program is necessary for the protection of freshwater resources (Pesce and Wunderlin 2000). Since the data of water quality may be interpreted individually to explore the impact of the elements content in water to the environment and human health in accordance with the experiences and knowledge of personal experts, the results of water quality analysis become doubtful and yield uncertain information (Fulazzaky 2005). The assessment of river quality is Water Air Soil Pollut (2010) 205:63–77 DOI 10.1007/s11270-009-0056-2 M. A. Fulazzaky (*) : T. W. Seong : M. I. M. Masirin Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Parit Raja, Batu Pahat, Johor 86400, Malaysia e-mail: fulazzaky@gmail.com