Physiochemical parameters and macroinvertebrates together can give better picture of any wetland ecosystem. The major objective of this study was to assess the water quality of Balkhu Khola and its impact on structure and function of aquatic ecosystem. But this study was focused particularly on identification of the biological indicator of water pollution especially benthic macroinvertebrates along with physiochemical parameters. The water samples and bottom sediments were collected from upstream and downstream courses of Balkhu Khola in July, August and September 2003 and February 2004 and analyzed in the laboratory. Altogether 10 texa of invertebrates belonging to four phyla were recorded. The major groups identified were Oligochaetes, Diptera and Bivalvia. They show negative correlation with dissolved oxygen and positive correlation with carbon dioxide content. The values of physiochemical parameters were significantly different except temperature between upstream and downstream courses of river. The water was found more polluted at downstream course of Khola. Detailed study is essential to control the pollution in Balkhu Khola. Immediate preventive measure for direct discharge of sewage and industrial effluents and disposal of solid waste should be taken along the river course.
