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The temporal and spatial distribution patterns of chlorophyll-a and its correlation with the main environmental factors were analyzed according to the monthly investigation from January,2007 to December,2009 in Lake Qiandao where a large number of silver carp and bighead carp stocked.Results showed that the concentration of chlorophyll-a in sampling stations located in the upper reach riverine and transitional zones of the reservoir showed a significant seasonal variations with two concentration peaks occurred in spring and late summer or early fall,respectively.The concentrations of chlorophyll-a in upstream sites(in the riverine and transitional zones) were significantly higher than those of downstream sites.The chlorophyll-a during the warm season was usually stratified with a concentration peak occurring at depths between 4m and 12m,occasionally at a depth of 20m.The result of correlation analysis showed a weak correlation between chlorophyll-a and NO2-N,CODMn,water temperature(WT) and silicate(SiO2-3),while no significant correlations of the chlorophyll-a were found with other environmental factors,especially with the TP in the water.The regression equation between chlorophyll-a and the correlated environmental factors could be expressed through the multiple linear stepwise regressions as:Chl.a=0.114 WT+2.120 CODMn +17.157 SiO2-3-37.391 NO2-N-1.946.