Comparative Analysis Of Three Deep Reservoirs Eutrophication Characteristics, Guizhou Province.

Eutrophication is a global environmental problem, Guizhou is located in the upper reaches of Yangtze River and Pearl River, its water quality directly affects downstream. The study of the eutrophication characteristics and influence factors is of great significance. Longtan Reservoir, Wanfenghu Reservoir and Sanbanxi Reservoir were investigated during November(dry period) 2012, April(level period) and July(wet period) 2013. Including environment factors, eutrophication indicators, phytoplankton flora and fauna characteristics. Using the trophic state index, trophic level index, biodiversity index for Reservoir eutrophication evaluation analysis, the results showed that:(1) 3 Reservoirs showed different eutrophication level, the eutrophication level of Longtan Reservoir was lower, from oligotropher to mesotropher level; Wanfenghu Reservoir was of mesotropher to light eutropher level; Sanbanxi Reservoir was higher, from mesotropher to middle eutropher. The eutrophication level was different by time, it was lower in the dry period, and higher in the level wet period; By the vertical section, The eutrophication level was the same in dry period, and it decreases with the increase of water depth in the level period and wet period but at below the 60 m layer, the extent of eutrophication increased slightly affected by the increasing of total phosphorus concentration. Therefore, the eutrophication degree of upper and lower layers was higher, the middle layer is lower, we can take water from the middle layer,in order to ensure the quality of drinking water.(2) All of the three deep reservoirs have water thermal stratification, it was single thermocline structure in the dry period, the thermocline in Longtan Reservoir, Wanfenghu Reservoir and Sanbanxi Reservoir were at 60~80m, 40~60m and 50~70m. It was stratified from top to bottom in level period and wet period. The Euclidean distance clustering analysis, it was divided into the upper and lower layers of dry period, and divided into upper, middle and lower layers in level period and wet period. The thermal stratification dominate the stratification structure of other environmental factors, and thus indirectly affect the stratification of eutrophication.(3) The eutrophication level of phytoplankton instructions were as follows: Sanbanxi Reservoir in Eutropher level, Wanfenghu Reservoir in Mesotropher level, Longtan Reservoir in oligotropher level, the evaluation results were in conformity with trophic level index Zooplankton indicates three Reservoirs all in Mesotropher level,and the eutrophication of comparison was different with trophic level index and the evaluation results of phytoplankton, therefore, the evaluation results tend to in favor of trophic level index.(4) The layers of surface to 20 m were the most active layer for phytoplankton, and the most significant change layers for water temperature, dissolved oxygen, p H and some other environmental factors, The total phosphorus pollution load was higher at the lower layer of Longtan Reservoir and Sanbanxi Reservoir lower, the seasonal water convection makes the underlying higher concentration of nutrients spread to the upper water, which easily to induce phytoplankton bloom.