Abstract
In this study, we discuss the storm runoff load for a collective tea field catchment. The study area was Makinohara plateau, in Shizuoka, Japan. The water quality and discharge were measured during a storm period. Heavy rain occurred due to a Bai-u front or cyclone during the rainy and typhoon seasons from June to September. Compared with clear weather days, NO3-N concentration during heavy rain decreased to 1/3. However the T-P and COD concentrations increased 2∼23 times. The average recovery rate of NO3-N concentration was 3 mg · l-1 · d-1. Hysteresis was observed in the relation between the discharge and the loads. The loads NO3-N becomes higher when discharge was decreased than when it was increased. On the other hand, the load of T-P showed a reverse tendency, and the load of COD was similar, too. The loads in periods of storm runoff are heavily affected by the amount of rainfall and antecedent conditions.
