Abstract
Analyzing the water quality biologically by the biotic index ($\beta$) of Beck-Tsuda method, for four sites of the water system of Namcheon River which reaches a length of 19.5km and flows through the kyungsan-town and Namcheon-myun in Kyungsan-gun of the suburbs of Taegu and extends to the Gumho-river on the lower, the results are summarized as follows: 1) An indicator species collected from the water system of Namcheon River comprises 78 species. Among them, 27 species are intolerant species and 51 species are tolerant species to water pollution. 2) The water of 2 sites, Weondong-bridge, Sanjeon-iron bridge was clearly water, oligosaprobic zone. The water of Youngdae-bridge was slightly polluted water, $\beta$-measosaprobic zone. But the water of Maehoildong bridge was severely polluted water, polysaprobic zone. 3) The Namcheon River was mainly polluted with sewage from the kyungsan town, with industrial wastes and products from many factories surviving the town. 4) The pH wate system of Namcheon River was alkalescent. 5) The map showing a class of water quality analyzed biologically was also prepared for each site of the water system of Namcheon River, Kyungsan. 6) It is requested that a waste water disposal plant should be established near Youngdae-bridge and Maehoildong-bridge respectively.