Characteristics and Influencing Factors Analysis of Spatio-Temporal Variations of Water Quality in Tangpu Reservoir and Its Tributaries

Cluster analysis and principle component analysis were used to analyze the spatial and temporal characteristics of water quality near and in Tangpu Reservoir.Cluster analysis showed that according to the similarity,water quality of Tangpu Reservoir can be divided into 3 typical spatial areas including tributary,reservoir bay and reservoir,and 3 seasons including heavy rain,rain,and non-rain.Principle component analysis indicated that:(1) Water quality in downstream of two tributaries Nanxi and Beixi was mainly affected by the pollutant discharge upstream cities and towns.Because of slower velocity,some pollutant became the key factors affecting the water quality in reservoir bay,such as trophic level,algae growth and organic pollution.Water quality in reservoir was mainly affected by primary productivity fluctuating with season and inorganic salt.(2) In June,for continuous heavy rain,water quality is mainly affected by terrestrial pollutant loading by heavy rain and runoff erosion.In rain season(May,July and August),the characteristics of water quality in reservoir resulted in algae growth with increasing temperature and intense nitrification by bacteria and microorganisms.In non-rain season(from January to April and from September to December),water quality in reservoir is mainly affected by interact of and meteorological factors and water level.