Chemistry of Stream Water and Mass balance in a Forested Headwater Catchment

Abstract

Chemical study of the stream water was continuously conducted from March, 2000 to November, 2003 in forested headwater catchment at Ina, Nagano Prefecture. Chemistry of stream water changed at the rain events and the snow melt season, as increase runoff. When temporary runoff was increased by the rainfall, the decrease in the pH was observed as episodic NO₃^- concentration increased. The precipitation element was becoming about 40% in the peak of runoff, result of the two component hydrograph separations. In the snow melt season, NO₃^- concentration was episodic increased with increased runoff at the early stage, however NO₃^- concentration was decreased with increased runoff. The mass balance in the catchment was calculated. The discharge of cation and SO₄^2-­ was more than deposition. On the other hand, the NO₃^- deposition was more than discharge. The discharge and deposition of Cl^- was balanced.