Saturation of water with oxygen is an important technological step in improving water quality. In practice, this is achieved by forced aeration using special technical facilities — aerators. The conventional pneumatic, mechanical, and physicochemical methods of aeration require energy for their realization; many aerators are complex in design and need skilled servicing [1 – 3]. For oxygen saturation of water, the chute can be used as a component of specialized engineering systems for water treatment intended for improving water quality. In hydraulic engineering, the chute is commonly used as a spillway structure in which the aerators (if available) serve to supply air for protecting the cement concrete lining from cavitation erosion [4, 5]. Here we propose to use a chute equipped with aerators for the oxygen saturation of water under conditions that provide a sufficient water drop. In the spillway, the water stream is saturated with air either by self-aeration, or in the flowseparation region, upon the exit of the water stream from the aerator. From the air bubbles dispersed in water, oxygen is transported into the fluid. This technology for improving water quality requires but moderate energy expenditure. The experimental setup that we used in our studies is shown in Fig. 1; it was designed in a laboratory of the Department for Hydraulic Research at the NIIES Joint-Stock Co. The setup operated in the following manner. Water from reservoir 1 was conveyed by means of pump 2 into vertical feed tank 6 from which it was allowed to flow freely by gravity through chute 7 to return back to reservoir 1. The slope of chute channel was i = 0.57; the chute length and the chute width were, respectively, L = 4.32 m and b = 0.1 m. Three flow aerators, each designed as a step (hst = 18 mm), were located along the length of the chute spaced at distances of 1.29, 2.29, and 3.29 m from the chute entrance. The flow rate in our experiments varied from 1.9 to 4.6 liter sec; the inlet flow depth was 40 – 55 mm and the outlet flow depth was 9 – 18 mm. The following test regimes were considered: I — the three aerators were open, and the flow transition to the reservoir was effected in a ski-jump mode; II — the three aerators were closed, and the flow transition to reservoir was effected in a ski-jump mode; III — the three aerators were open, and the flow transition to reservoir was effected in a sub-level immersion mode (the drowned chute extension length was L1 = 4.92 m; see Fig. 1); IV — the three aerators were closed, and the flow transition to reservoir was effected in a sub-level immersion mode; V — the three aerators were removed from the chute, and the flow transition to reservoir was effected in a sublevel immersion mode. The experiments were run using a variable oxygen deficit method. The reservoir was filled with tap water to the needed level, the concentration of dissolved oxygen was measured, and sodium sulfite Na2SO3 was added to provide complete deoxygenation of the water, with gentle agitation of water in reservoir 1 for 1 – 2 h. Dissolved oxygen sensor 10 was put in place, the temperature in reservoir 1 was measured, and analyzer 9 was put in order for monitoring the dissolved oxygen concentration at the given temperature. With