Abstract:

This study investigated the water chemistry of Wujiangdu Reservoir and its response to river damming.Results showed that major ionic chemistry of the reservoir dominated by HCO-3,SO2-4,Ca2+ and Mg2+,which account for about 90% of the total solutes in the water.It is concluded that limestone weathering,among silicate rock and evaporation weathering,are the most important controls on the water chemistry.The reservoir showed clear temperature stratification,and hence induced different chemical composition of major ions in the water of different water layers.Accordingly,dissolved components appeared different distribution characteristics along the water column.Si and Chlorophyll showed a negative correlation with each other in the vertical profile,due to biological function such as algal absorption.Concentration of HCO-3 decreased from surface water to 30 m in depth and then increase downwards,controlled by both photosynthesis and organic decomposition.River damming and the ways of water discharge of the reservoir can change the water chemistry of the reservoir and discharged water.In Pianyan River and Xifeng River Ca2+,SO2-4,HCO-3 Mg2+,K+,Na+ and Cl- have contributions to Wujiangdu Reservoir.Fish feeding,sewage inputs,fertilizer use and acid rain deposition are the possible contaminant sources for the reservoir water.

Key words: river water chemistry/river damming/temperature stratification/chemical stratification/Wujiangdu Reservoir