English: The researcher of the Institute of Hydrobiology of the National Academy of Sciences of Ukraine determines the optical properties of the water masses, in particular the transparency and color of water in Kyiv and Kaniv reservoirs. These characteristics are essential in assessing and forecasting water quality and water productivity. The indicator of water transparency is measured by the white Secchi disk with a diameter of 30 cm, which is gradually immersed in water from the shadow side of the boat to the depth of its disappearance. The color is determined using a standard color scale (Forel-Ula's scale) from the shadow side of the boat on a white disk, immersed in a body of water to a depth equal to half the transparency. These studies were carried out during the expedition to the Kaniv Reservoir as part of the research project "The impact of overgrown reservoirs with higher aquatic plants on flowering processes and fish productivity".