Abstract: In order to find out the status for pollution from aquaculture tail water in the Chaohu Lake Basin,the water quality of the aquaculture tail water of several major freshwater species in the basin was monitored in April, July, September and November 2019. The dynamic changes of physical and chemical factors of the water bodies were analyzed. The single-factor pollution index method was employed for individual evaluation of pH, dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH+4-N), and permanganate index (CODMn), and the Nemerow pollution index method was applied for overall evaluation on the water quality of each monitoring site.The results showed that the contents of pH, TN and TP were in line with the Level II standard of stipulated in the Freshwater Pond Aquaculture Water Discharge Requirements, and the contents of DO, NH+4-N and CODMn exceeded the standards in some sites. The results of single-factor pollution index analysis showed that the tail water was not polluted by pH, TN and TP. The proportions of monitoring sites with pollution factor of DO, NH+4-N and CODMnwere 12.5% , 25.0% and 87.5% respectively. The results of Nemerow pollution index calculation showed that 75% monitoring sites were at the slightly or moderately polluted level.The main pollutants of aquaculture tail water in Chaohu Lake Basin was CODMn. The pollution status was serious.

Key words: Chaohu Lake basin, aquaculture tail water, water quality evaluation, single-factor pollution index, Nemerow pollution index