TOWARD THE GLOBAL-SCALE ESTIMATION OF WATER RESOURCES WITH A COUPLED MODEL FRAMEWORK OF HYDRO- AND THERMODYNAMICS IN RIVERS AND LAKES

Abstract

 Evaporation from natural lakes and artificial reservoirs is a loss of water resources, but existing estimations of it are based on simplified methods. The evaporation is a phenomenon related not only to in-lake thermodynamics but to change in water surface area driven by riverine in- and outflows, so this study reestimates it on a global scale with a coupled model framework of hydro- and thermodynamics in rivers and lakes, of which estimate is consistent with previous ones. It was found that evaporation per area from reservoirs is bigger than that from natural lakes due to the difference of spatial distribution, and reservoir construction increases evaporative loss due to warm-up of water surface temperature, in addition, to increase in surface area. The estimation of storages in each water body also showed that most of the residence time is caused by lakes. These results suggest that it is important to consider the thermodynamics of lakes and the interactions with rivers for the estimation of water resources and their quality.