Eutrophication of Main Storage Reservoir in Macau

Eutrophication of a raw water supply reservoir in Macau, namely Main Storage Reservoir (MSR), was analyzed in this study. The reservoir is a pumped storage reservoir that receives water from the West River of the Pearl River network 20 km away. In recent years, there were reports that the reservoir experienced some problems of algal bloom, and the situation appeared to be worsening. To understand the eutrophication process of the reservoir, totally 18 monthly water parameters including 5 hydrological parameters (precipitation, imported volume, exported volume, water level and hydraulic retention time (HRT)), 4 physical parameters (temperature, pH, turbidity and conductivity), 7 chemical parameters (dissolved oxygen (DO), Ammonium, nitrite, nitrate, total nitrogen (TN), orthophosphate (PO4 3- ) and total phosphorus (TP)), and 2 biological parameters (phytoplankton abundance and chlorophyll-a) were sampled and monitored in 2010. The correlation analysis was conducted to determine the dominant parameters that were correlated with the phytoplankton population. Principle component analysis (PCA) followed by multiple linear regression (MLR) stepwise method was used to simplify the complexity of the relationships among 10 selected parameters, and to predict phytoplankton abundance level using the selected principle component scores (PCS) of the principle components (PCs) with eigen values greater than 1, as independent variables The results showed that the trophic state indices (TSIs) of MSR were estimated as 58-72 for the whole year, indicating that the reservoir was in eutrophication – hypereutrophic status. There was a seasonal variation on eutrophication level with one peak of the phytoplankton population in the late summer, suggesting that temperature was an important factor that causing the bloom. The phytoplankton abundance was at low level (