WATER QUALITY ASSESSMENT OF THE SEMENYIH RIVER BASIN, SELANGOR, MALAYSIA

The aim of this study is to investigate the hydrological characteristics and water quality in the Semenyih River Basin in relation to land development in the surrounding areas. Results of analyses of selected water quality parameters such as BOD, COD, DO, NH3-N, TSS, TDS, pH, Fe, color and total nitrogen showed increase in pollution levels due to human activities associated with urbanization, industrialization, agriculture and mining/quarry activities. The range of deterioration in water quality varied depending on the percentage of change in land-use. Based on land use, the Semenyih River Basin can be divided into 3 different categories as follows: the upstream (forested) area which can be classified as being slightly polluted; the middle (settlements and industrial areas) which can be classified as being moderately polluted; the downstream (urban) area which can be classified as being highly polluted. Since the Semenyih River Basin is one of the major sources of surface water supply for the Klang Valley area, it is important that the land-use activities within the basin be carefully planned and controlled to preserve the water resource as well as the quality status.