To overview the stream water chemistry in Japan, we conducted systematic stream water sampling and chemical analyses as the Japan-Wide Stream Monitoring (JWSM) 2003. The total numbers of 1278 samples from head water streams from all over Japan were analyzed in this study. The Japanese average values and concentrations of E.C., pH, Cl-, NO3-, SO42-, Anion deficit (HCO3-),
Na+, NH4+, K+, Mg2+ and Ca2+ were 7.01mS/m, 6.84, 120μmol/l, 25.7μmol/l, 60.1μmol/l, 341μeq/l, 216μmol/l, 6.1μmol/l, 16.2μmol/l, 53.7μmol/l, 133μmol/l, respectively. Stream water chemistry calculated at every prefecture showed regional distributions, background level of natural stream chemistry was quite different depended on the area in Japan. NO3- concentrations showed most distinctive difference, Saitama prefecture (113μmol/l) was more than 13 times higher than Hokkaido prefecture (8.2μmol/l).
