Study on Physiochemical Parameters and Benthic Macroinvertibrates of Balkhu Khola in Kathmandu Valley, Central Nepal Susmita Dhakal Email: sdhakal@icimod.org dhakal_sus@yahoo.com Tel: 977-9841545799 Paper presented on “Management of Water, Wastewater and Environment: Challenges for the Developing Countries” held in 13-15 Sept 2006, Kathmandu Abstract 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. Keywords Biological indicator, discharge; disposal, macroinvertebrates, Physiochemical parameters Introduction Water is an important and essential substance in protoplasm and is the basis of life. It has been responsible for evolving life in our planet. It represents the great circulation system of the earth, being it as the sap of plants, the blood stream of animals, and rainfalls on the surface of the lands of rivers flowing to the sea. Many lower organisms live in direct contact with water, in higher animals the cells are in contact with the intercellular fluid containing water. It serves as transport medium for nutrients hormones and enzymes inside the body. Water is the most abundant and renewable resource, which helps to maintain the earth climate and dilute environmental pollution. Water is essential for life next to the air. Water is found to be 50% to 97% by weight to all plants and animals and about 70% of human body. 1