Eutrophication Evaluation Of Large And Medium Reservoirs In Guangdong Province And Design Of Water Quality Management Information System

Because of the geological structure reasons, natural lakes is few in Guangdong province. Building reservoir constructions became the main means to adjust the temporal and spatial irregularities of the water resource. Reservoir water supply plays an important role in Guangdong province. With the rapid economic development, ecological system of reservoirs has been largely disturbed with human beings activities. The eutrophic levels of Guangdong province increased significantly, especially in those reservoirs close to cities with high population density.In order to make a comprehensive study of the actual status of reservoir eutrophication, 19 representative reservoirs distributing in 6 main basins in Guangdong province are selected in this thesis, analyzing and diagnosing their eutrophic levels and reasons, and their actual eutrophic status and their characteristic of eutrophication. Finally, a water quality management system was built for Gaozhou Reservoir with Arc View.Among the 19 selected reservoirs, the TN, TP, Chl-a, BOD5, COD, and SD are with 0.120-7.151, 0.001-0.830, 0.003-32.360, 1.00-7.11, 0.02~7.04mg/L and 0.40~6.3m respectively. The result shows that the reservoirs were not polluted by the organic pollution, if so, always those reservoirs locating in developed areas in the downstream watershed. The trophic status index TSIC ranges from 21.64 to 57.15. For each reservoir, the index is different in dry and flood seasons. Based on the average index over the two seasons, there are 3 oligotrophic reservoirs locating in economically developing towns upstream; and 2 eutrophic ones situating in developed towns downstream; and 14 mesotrophic ones trending toward eutrophic status.The main characteristic of trophic level of each watershed is: The degree of eutrophication is more serious in flood season than in dry reason, in upstream than in downstream along the watershed. The degree of eutrophication is low at large in Dongjiang watershed, while it is high in littoral and the downstream area of Pearl delta area, and it is medium in Beijiang watershed.The main characteristic of trophic level of each reservoir is: The degree of eutrophication is more serious in flood season than in dry reason in the same reservoir, while the eutrophic degree is more serious in water entry than in the dam.The main characteristic of eutrophication of volume size among reservoirs is: For large reservoirs, the degree of eutrophication is more serious in flood season than in dry reason, while it is more serious in medium and small reservoirs than large ones in dry reason.The result of phytoplankton investigation shows that there are 7 phyla, 89 genera and 142 species. Cyanophyta is the preferential species of eutrophic water body, while the Chlorophyta is the representative species of mesotrophic water body. Through the distribution of algae, we can deduce the pollution level along the watershed. Dominant species appear in reservoirs in the downstream of the watershed.With Arc View, we built a reservoir water quality management information system, offered a visual tool for water quality management.