Abstract:Tangxi Reservoir, located in the east of Guangdong Province, China, near latitude 23.5 degrees north, is an important drinking-water reservoir for local people. From latter 1990‘s, Tangxi reservoir has been in an unhealthy eutrophic state, and cyanobacteria bloom was frequently observed. As climatic characteristics in the latitude Tangxi reservoir located, suitable water temperature for the occurrence of cyanobacteria bloom(25~35℃)was always observed from April to November, and generally, flood season, duri...