Reservoirs occupy a large portion of water resources in Japan. Therefore, in this study, relationship between watershed conditions and nutrient concentration, loading and inorganic ratio of inflowing river to reservoirs was investigated by statistical analysis. 52 reservoirs were chosen from all over Japan. The mean concentration of total nitrogen was strongly influenced from artificial factors in basin. Phosphorus and nitrogen loading were estimated by two ways; multiple regression analysis or equations obtained by multiplying influent quantity and nutrient concentration. Those equations were capable of estimating nutrient loadings of inflowing river with high precision.
