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Published on: October 21, 2016
Seasonal variations and hydrological management regulate nutrient transport in cascade damming: Insights from carbon
Yujing Yang1, Wanfa Wang1, Shengde Yu2
1Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang 550025, PR China; College of Resources and Environmental Engineering, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guiyang 550025, PR China.
Abstract:
Reservoirs around the world have significantly altered the natural transport of nutrients in rivers. However, the specific effects of the cascade damming on the migration, transformation, and environmental consequences of these nutrients remain unclear. To address this knowledge gap, we analyzed spatiotemporal variations in water chemistry, nutrient concentrations, stable isotope of dissolved inorganic carbon (δ13CDIC) and nitrate isotope (δ15N-NO3-) in seven cascade reservoirs along the Wujiang River, each characterized by different regulatory regimes. Our findings reveal that the average absolute changes in concentrations of total nitrogen (TN), total phosphorus (TP), and silicon dioxide (SiO2) during the wet season (WS, spring and summer) were 2.4, 1.4, and 1.1 times higher than those observed in the dry season (DS, autumn and winter). During the WS, the average apparent retention efficiency (*RETf) values in the Hongjiadu reservoir were 97 % for TN, 98 % for TP, and 95 % for SiO2, indicating substantial nutrient consumption in the cascading reservoirs. Conversely, during the DS, the *RETf values for TN, TP, and SiO2 were negative, suggesting notable nutrient accumulation within the reservoirs. The nutrient fluxes released downstream from the cascade reservoirs in the Wujiang River were significantly greater than the upstream inflow fluxes. These findings help demonstrate how downstream discharge across cascade reservoirs amplifies nutrient flux disparities due to dam construction. Our study enhances the understanding of how cascade dam construction impacts nutrient dynamics, supporting the optimization of reservoir operation models and advancing scientific water resource management and conservation efforts.
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