Seasonal concentration distribution of dissolved manganese forms in Novosibirsk Reservoir water is studied. Currently Novosibirsk Reservoir resources perform the function of water supply and are also used for irrigation, fish-farming and recreation. The ecological and physiological role of manganese in the life of higher plants, algae and hydrobionts is very high. Taking an active part in migration cycles manganese is accumulated in various water ecosystems components. Dissolved manganese concentration in Novosibirsk Reservoir water undergoes significant seasonal change as well as from top to bottom of water column. Manganese ions concentration increase in surface waters of Novosibirsk Reservoir is caused by the reduction of Mn (IV) to Mn (II). It is shown that oxygen concentration changes, redox and рН conditions influence manganese mobility in water. Inverse correlation dependence of Mn (II) on oxygen concentration and redox conditions in surface water of reservoir has been established. The main dissolved manganese (II) inflow from bottom sediments into bottom waters and then into water column has been found in summer and winter periods.