Aha reservoir, 6 kilommters away from southwest Guiyang City, Guizhou Province, is major source for drinking water of Guiyang City. Normal stage of this reservoir is 1108. 0 m; reservoir capacity 44. 5 million m³; and the water depth 26m. The dead stage and reservoir capacity of dead water are 1090m and 2.7 million m³ respectively. As an artificial lake, seasonal oxygen shortage is one of vivid characteristics of Aha,reservoir polluted by waste water containing Fe, Mn from coal mine. Results from years measuring of vertical water column of 20m depth in different seasons show that Fe and Mn distributions vary with different seasons and different temperture strata of water, and the vertical water temperature is in isothermal status from winter to earlier stage of spring, during which concentration of Mn and Fe in water is less than 0. 01 mg·L^-1 and 0.05 mg·L^-1 respectively. During summer and autumn, reservoir will be stratified according to different temperatures. Upper stratum is in oxygen rich status, with Mn and Fe concentration of less than 0. 1 mg·L^-1 and 0. 3 mg· L^-1 respectively, and the middle and lower strata are in status of low pH, oxygen shortage or lower oxygen, at which, Fe concentration is more than 0. 3 mg·L^-1 while Mn concentration is as high as 1.086 mg.L^-1，which is indentified to be closely rele-vant to oxidation and reduction reaction of high concentration of Fe(166000 mg · L^-1) and Mn (18800 mg·L^-1) contained in the reservoir sediment. The study provides a guideline of pumping at the optimum depth according to the optimum qaulity of water for water plant.