2001 Volume 45 Pages 1009-1014
Soluble substances of the Kinokawa-river increased down the stream. Excluding weathering of limestone, soluble substances in the upper stream of the catchment covered with forest were very low and main components were HCO-3, SO2-4, Na+, and Ca2+. Soluble substances in the upper stream of the forest catchment with limestone were high and the main components were Ca2+ and HCO-3 Ca2+ and HCO-3 concentrations increased from the upper stream to the middle stream with forest, but Na+, Cl- and SO2-4 concentrations remained unchanged because of weathering of limestone and feldspar. In the lower stream of the catchment with farm land and housing site, the concentrations of Na+, Cl-, NO-3 and SO2-4 were very high. It was concluded from the relation between land uses and water qualities that Na+ and SO2-4 origin were farmland, and Cl- origin was sewage respectively, and NO-3 was derived from both origins. Isotopic study of oxygen and hydrogen indicated that the river water originated from precipitation and isotopic ratios depended on mainly precipitation altitude.