Water quality fluctuation of an irrigation channel in abandoned rice paddy fields in Koza Hills, Kanagawa Prefecture

Abstract

Recently, many paddy fields in hilly areas have been abandoned in Japan. However, there are still small streams, which were irrigation channels, after abandoned. We focused on their water quality and fluctuation. An irrigation channel was selected in Koza Hills, Kanagawa Pref., which flows through abandoned rice paddy fields and is still maintained. Temperature, water temperature, velocity of flow, depth and width of channel, pH, electric conductivity (EC), T-N, T-P, NH4-N and chemical oxygen demand (COD) were investigated at five points from July to November 2009. There was an outfall of waste water at the top of channel. Then, EC, T-N and COD were declined from headwater to down stream.