FIELD: hydraulic engineering. SUBSTANCE: air bubbles 4 are fed into water flow 1 supplied to working wheel 2 of a hydraulic machine 3. Bubble formation is carried out in the area located below center line 5 of stream 1 to form groups of uniform bubbles placed in line. The device to implement the method has air compressor 7 connected with air line 8 to the aid for bubble forming. The aid is made in the form of at least one tube 9 placed crosswise stream 1 and provided with an opening. Length of air line 8 provides tube 9 presence in the area of stream 1. The tube is placed below stream center line 5. Options to implement the method are presented. EFFECT: protection of plankton. 8 cl, 6 dwg
