Study on Water Balance of Terraced Paddy Field by Field Observation and Numerical Model

Recently, terraced paddy fields, called Tanada, have been reduced in Japan. However, it is considered that Tanada is an efficient water use system and has preferable effects on environmental conservation. In this study, in order to make clear the water balance in Onakao Tanada, the geographical characteristics were surveyed and numerical model was developed as tank model. From the observed results, it is cleared that Tanada is an efficient land use system in steep area and has complicated water flow network. Computed results show that water supplied from agricultural channel are stored in each Tanada according the flow network, and distributed in stepwise in space and time. furthermore, it is clear that infiltration and evaporation are becoming very important factor in water balance system at Tanada