Abstract: The spatial and temporal changes of ten water quality indicators obtained monthly from August 2018 to October 2019 in seven water systems of Jinyin Lake in Wuhan were investigated by constructing a water quality crucial index model (WQI_min) consisting of four crucial indices, namely, five-day biochemical oxygen demand (BOD₅), permanganate index (PI), chemical oxygen demand (COD), and dissolved oxygen (DO) using principal component analysis. Result demonstrated that the water quality in Jinyin Lake differed notably in spatial scale: Dongyin Lake, Shangjin Lake, and Moshui Lake in the upstream of Jinyin Lake belonged to polluted area of inferior water quality with the WQI_min values ranging between 25.63 and 31.79; Dongda Lake, Xiajin Lake, Xiayin Lake and Shangyin Lake in the downsteam were low-polluted areas of medium level with their average WQI_min values ranging from 45.64 to 53.19. In temporal scale, water quality in Jinyin Lake can be divided according to three time periods: January 2019 witnessed the optimum water quality with an average WQI_min value amounting to 61.68; August 2018 to March 2019 (except for January 2019) undergone low pollution with the average WQI_min value from 47.17 to 52.70; April 2019 to October 2019 presented inferior water quality with the WQI_min value from 24.41 to 35.95. The water quality in August-September 2019 declined compared with the same period in 2018 because of the increasing discharge of xenobiotic and endogenous pollutants. In conclusion, the water management of Jinyin Lake needs to be further strengthened.

Key words: water quality, WQI_min model, pollution indicators, temporal and spatial characteristics, ecological system, Jinyin Lake in Wuhan