Daily observations of dynamics of spectral light attenuation (ε, m^-1), chlorophyll «a» concentration (C, mg/m³) and water temperature (Т, °C) at different depths of Lake Krasilovskoye (Altai Krai) was conducted in June 2013 and May 2014. The sampling in pelagic part of the lake was carried out every two hours (to estimate ε and Т) and every six hours (to evaluate C). Thereafter, spectral water transparency in the wavelength range of 400–800 nm was measured with a spectrophotometer ПЭ-5400УФ, and the samples of phytoplankton algae were filtered in situ. Summer vertical daily measurements of ε shows that the curve of attenuation dynamics for the bottom layer is in phase opposition with the corresponding curve for the surface layer. This fact has not been observed during the studies in May. In spring, the samples taken at the surface and at the bottom shows the shift of ε maxima in time, namely, the maximum for the bottom layer is observed at 2 a. m. (02-00) and for the surface layer — at midnight (00-00). The data on chlorophyll concentration and water temperature reveals that in summer in the surface layer these two values were in phase opposition, i. e. Т is inversely dependent on C. On the contrary, in spring the direct water temperature dependence of chlorophyll concentration with a peak at 6 a. m. is evident. The daily observations in summer 2013 and spring 2014 shows absolutely different dependencies and correlation of water body characteristics that is, primarily, due to the seasonal changes of lake parameters themselves and direct affection of the hydrological processes on the studied parameters.