MODELING OF RADIATION SHADE FUCTION CONSIDERING SEASONAL CHANGE OF LEAF AREA INDEX OF RIPARIAN VEGETATION

Recently, multiple functions of river riparian vegetation are attracted in biological, environmental river engineering field. The decline of riparian vegetation strongly affects the river thermal environment, which also has a large impact on the ecological systems. In this study, a model that relates stream temperature with riparian vegetation was developed. The Nam Song River, which is a tributary of the Nam Ngum River flowing through the Vientiane Metropolis, was selected for field study. Meteorological data (air temperature, relative humidity, wind speed) were used, and the sink or source terms of the heat transfer equation were estimated from that data. NDVI (normalized difference of the vegetation index) remote sensing data was used for estimation of LAI (leaf area index) seasonal change. Simulations were made with several cases of riparian vegetation density, showing that river water temperature is more sensitive to river discharge change in the case of low density condition.