INFLUENCE OF RUNOFF OF INORGANIC IONS FROM FOREST AND ORCHARD ON RIVER WATER CHEMISTRY

Abstract

In order to evaluate the relationship between land use and river water chemistry, inorganic ion concentrations were monitored in the Kishi and Zakuro Rivers. The drainage basin of the Kishi River is mainly covered with forest and the orchard is widely distributed in the lower stream of the Zakuro River. In the Kishi River, the concentrations of Ca²⁺, Mg²⁺, K⁺, HCO₃^-, SO₄^2- and NO₃^- gradually increased down the stream. On the other hand, the concentrations of Na⁺ and Cl- did not changed in the upper and middle streams and sharply increased in the lower stream where the residential area and paddy field made rapid progress. In addition, the concentration of NO₃^- increased and the others decreased with increasing flow rate due to rainfall. Contrary to this, in the Zakuro River, the fertilizer used in orchard has affected the concentrations of NO₃^-, SO₄^2-, Mg²⁺ and Ca²⁺