Changes in sediment, nutrients and major ions in the world largest reservoir: Effects of damming and reservoir operation. (10th October 2021)

• Record Type: Journal Article
• Authors: Li, Siyue; Xu, Y. Jun; Ni, Maofei
• Is Part Of: Journal of cleaner production. Volume 318(2021)
• Publication Date: 2021-10-10
• Subjects: River damming -- Reservoir operation -- Three gorges reservoir -- Yangtze (changjiang) -- Water quality -- Water chemistry; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2021.128601
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: River damming and reservoir operation alter hydrological process, raising concerns over far-reaching influence on fluvial water, biogeochemistry and sediment fluxes due to the common occurrence of fragmented river landscapes around the world. Here, we investigated carbon, nutrients, and geochemical conditions in the world's largest reservoir, the Three Gorge Reservoir (TGR) in China, under three different dam operations. We also analyzed long-term trends of sediment and geochemistry in response to the reservoir building and operation. We found a drastically reduced average sediment load of 32 ± 29 Mt/y during the post -TGR, which accounts for only 6.4% of the average annual sediment load (501 Mt/y) during the period, of 1950–2000. Cumulatively, over 2004–2018, sediment inflow to the TGR totaled 2090 Mt and sediment outflow (i.e. downstream of the TGR) was 480 Mt, resulting in a total of 1610 Mt (or 77%) sediment trapped in the Reservoir, equivalent to 107 Mt/y. The reservoir water is geochemically dominated by Ca 2+ and HCO3 − with low-moderate mineralization and excess nutrients. Concentrations of carbon, nutrients and major ions differ notably in response to reservoir operations with the highest nitrogen level under the sluicing period (SP). Major cations concentrations are low in the low water level period (LWLP), while major cations and Cl − and SO4 2− concentrations reach high in the SP. Concentrations of Cl −, SO4 2−, and Na + +K + increase 2-3-fold, increasing their relative abundance by a factor of 1.5–2. Nutrients show overall increases with considerable alteration of dominance for dissolved and particular species due to damming and anthropogenic inputs. Furthermore, dissolved inorganic nitrogen increases 8-fold during the last 50 years. The findings imply great effects of river damming and reservoir regulation on sediment transport, nutrient levels and major ion chemistry. Graphical abstract: River damming and dam operation result in profound changes in sediment, carbon, nutrients and major ions, with a drastic decline of sediment load and a progressive increase in Cl, SO4, and Na + K. Image 1 Highlights: 1.61 Gt sediment is trapped in TGR during 2004–2018 presenting a 77% retention rate. Nutrient and major ion levels respond to dam operation with highest N level in sluicing period. Ca and HCO3 are dominant in TGR while water quality is impaired by excess nutrients. Relative abundances of Cl, SO4, Na and K rapidly increase by a factor of 1.5–2 Nutrients and major ion levels are notably affected by dam and human activities.