The Environment Sedimentol ogical Study on Erhal Lake,Yunnan Province——Sediments particl a size distribution,f1ow direction and energy distribution

Key words: 
• Erhai Lake /
• environment sedimentology /
• particle size distribution /
• flow direction /
• energy distribution

Abstract: The superficial sediment layer in lake,only a few centimeters in thickness,may contain more organic matter,nutrients and anthropogenic pollutants than the entire water-cdumn. The particle sige distribution can be used to indicate the flow direction and energy distribution of the lake. The water energy and flow's feature controlled the nutrients and pollutants distributions in the lake. In the light of research results about particle size distribution,cluster analysis and factor analysis,the author surmises that there are several types of lake flows with different direction and power existing in Erhai Lake.First,there is a flow from Miju River,which is the biggest input river of Erhai Lake,forming the primary dynamic flow. Second,the Cangshan streams along the western side of Lake Erhai forms the radical canal flows from west side to the east,which are diminished gradually,and built fan delta along west side.Third,along the west side,exists lake flows with the direction from north to south;fourth,affecting by the topography of Lake Erhai,there are three relatively big annular flows in Lake Erhai with anticyclone direction. In a word,the flows' features control nowadays size distribution framwork.