Abstract
In this study, water quality prediction and verification were carried out at the newly-constructed Jozankei dam reservoir (Lake Sapporo), located in the southern part of Sapporo city, Hokkaido.
Field observations with the aim of estimating the pollutant inflow load to the Jozankei dam reservoir had been carried out since 1975, and the results of these observations were used to predict the water quality by the phosphorus-loading model. Phosphorus-loading model was also applied to Hoheikyo dam reservoir (Lake Jozan, an oligotrophic lake) and the model was shown to be reliable, thus confirming the usefulness of the phosphorus-loading model for water quality prediction. The water quality in the Jozankei dam reservoir was predicted to become oligotrophic or mesotrophic.
Field observations have been carried out at the Jozankei dam for period of 6 years since 1989, which was the first year of storage, for the purpose of verifying prediction results. After 3 years trial storage, full operations were commenced in 1992.
During the first 2 years after the beginning of storage, the TP concentrations were higher than the predicted values due to the nutrient release from submerged soils and plants. However, after the third year, TP concentrations decreased to almost the same level as the predicted values, which confirmed that a stable and clean water quality environment was being maintained.
