2018 , Volume 23, № 6, p.107-114

Here we consider the summertime hydrothermal regime in a 124-km river occurring within the interval (reach) downstream of the Krasnoyarsk HPP on July 3, 2016 based on the deterministic modelling approach. The reach area is divided by 4 cross-section lines (0.5, 40, 77, 124 km) with gauging stations at the first, second and forth section lines to measure water temperature. Temperature measurements at the gauging stations are taken at time 𝑡𝑔 (at hour 08:00 and 20:00). Water temperature at the first gauging station was 7.2 ∘ C and remained constant during the time period under consideration. To carry out mathematical simulation by analogy with other authors, we use the Fourier equation. We have proposed a simple model for simulating summertime hydrothermal regime of a river based on calculation of water temperature in a coordinate system moving with water. The physically based estimation of water heat budget takes into account absorption of solar radiation by water surface, emission and absorption of atmospheric thermal infrared radiation (TIR) by water, convective heating of water as well as heat loss due to evaporative processes. The temporal fluctuation pattern of direct and scattered solar radiation depends on the zenith angle and atmospheric absorption. The dominant water heating factor is solar radiation during the daytime and atmospheric TIR at night. Emits TIR defined by the Stefan-Boltzmann law. Water temperatures 124 km downstream of the Krasnoyarsk HPP on the Yenisei River computed using the proposed model with consideration of morphometric characteristics are close to the recorded temperatures observed at the gauging stations, which proves that the deployed physical-mathematical model providing an adequate description of the actual hydrothermal processes. Our spatial-temporal analysis has revealed no diurnal fluctuations of water temperature, which we attribute to the fact that “cold” water leaving the dam enters the “warm” surrounding environment providing a permanent source of water heating.