The reservoirs gradually changed the distribution, source, and flux of particulate organic carbon within the Changjiang River catchment

Abstract

The increasing number of dams and reservoirs affects the delivery of fluvial particulate organic carbon (POC) to the sea due to their trapping effect. Here, we study the POC characteristics of the Changjiang River over three periods to explore the impact of reservoirs on POC sources and flux. We found that the Three Gorges Reservoir (TGR) significantly raised the proportion of riverine primary productivity (RPP)-derived POC downstream, while cascade reservoirs improved the RPP upstream. Since the beginning of TGR impoundment, POC flux into the sea has decreased, whereas the proportion of RPP-derived POC into the sea has gradually increased. Our results demonstrate that the TGR and cascade reservoirs changed organic carbon sources and improved the labile composition in the Changjiang River, which may adversely impact carbon storage. These findings could be applicable to other rivers affected by dams worldwide.