抄録
River water temperature has a great influence on the increase of phytoplankton and the habitat of fish, and it is dependent on hydraulic and meteorological elements. The surface heat balance, which is composed of net radiation, sensible and latent heat fluxes, is a non-linear function of water temperature. So a differential equation concerning river water temperature is non-linear. The surface heat balance has been treated as a regression quadratic equation of water temperature in some papers.
In this paper the following three trajectories of solution for one-dimensional non-linear heat balance equation are shown using Bernoulli's equation with a threshold value, convergence to an equilibrium temperature, constant value and divergence. The difference between non-linear and linear analyses of the river water temperature is investigated under some combinations of hydrological and meteorological elements.
