抄録
Attainment conditions of the water quality standard (COD) in Japanese 113 lakes (197 designated sites) were investigated by using observed COD concentration between 1978 and 1988. Observed concentration in about a half of all designated sites have exceeded the standard value of each site every year. Only 20% of the sites have attained the water quality standard every year. Objective 113 lakes could be classified according to two indices of ‘the ratio of exceeding year in 1978-1988’ and ‘the ratio of observed mean in 1978-1988 to the standard’. Though the attainment conditions throughout Japanese lakes have become better, the decreasing ratio of the autochthonous COD to the allochthonous indicated the emphasis of watershed management.
