XIANG Peng1，2，WANG Shilu1，LU Weiqi1,2，YANG Yuxue1,2，HUANG Qiangsheng1
(1, Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Environmental Geochemistry, Guiyang 550081;
2, University of Chinese Academy of Sciences, Beijing 100049)
Abstract: Cascade dams constructed in rivers have remarkable influences on global cycles of nutrient elements and aquatic environment through not only accumulating nutrients in the reservoirs and reducing the downstream output fluxes, but also changing the stoichiometric relations of different elements due to different retention mechanism and efficiency. In this paper, water samples were collected from seven large cascade reservoirs in Wujiang River Basin in September of 2013, July of 2014, and June of 2015; concentrations of total nitrogen (TN) and total phosphorus (TP) were determined, and the retention efficiency of N and P in the reservoirs were estimated. Results show that concentration of TN in the reservoirs of Wujiang River Basin gradually decrease from upstream to downstream, by 2%-13% in average, for each step reservoir. Low productivity and high oxygen concentration in the cascade reservoirs of the Wujiang river basin lead to a more efficient interception for P. However, the impact of highly-efficient retention of P is prone to be offset by exogenous P input due to the low P concentration in the reservoirs. The difference in interception efficiency of N and P in reservoirs leads to remarkable change in N:P in the water, and consequently causes change in environment and ecology in the water. Thus, the influence of interceptionof dams should be taken into account in the watershed management of controlling N and P.
Key words: Wujiang River Basin; cascade reservoir; nitrogen; phosphorus; Retention efficiency
EARTH AND ENVIRONMENT Vol.44, No.5 Tot No.313, 2016, Page 492-501
