Morphological Adjustment and Diversion Discharge Prediction in the Three Outlets Channel of the Jingjiang River

Abstract

The Three Outlets Channel (TOC) consisting of three anabranching rivers formed due to natural avulsion by extremely high floods, is the primary water–sediment channel connecting the Jingjiang in the middle Yangtze River and Dongting Lake (the second largest freshwater lake in China). Since the impoundment of the Three Gorges Reservoir (TGR) in 2003, the decreasing diversion of runoff and sediment load of the TOC has an impact on the hydrological connectivity of the river–lake relation. Nonetheless, it lacks complete understanding on the diversion of runoff and sediment load, erosion and deposition amount, and the calculation method of diversion runoff in the TOC. We used remote sensing images, hydrological data, and channel topography to analyze the change in runoff and sediment load, channel morphology, local erosion and deposition amounts. The main results show that: (i) Meander cutoffs of the Lower Jingjiang accelerated the reduction process of the Ouchi River’s runoff and sediment load and the increase in the number of dry days. After the impoundment of the TGR, the diversion of sediment load of the TOC was greatly affected, but the decreasing trend of the runoff diversion slowed down. (ii) The morphological change of the inlet zone of Ouchi River is larger than that of Songzi River and Hudu River. The morphological evolution of the inlet area led to the change in the diversion of runoff and sediment load of the TOC. (iii) In the dry season, the water level drop in the inlet zone of the TOC leads to a decrease in the diversion discharge. Therefore, considering the water level drop and channel width adjustment in the inlet zone, five empirical formulae for the diversion discharge of the five hydrological stations in the TOC are proposed. These empirical formulae can be used as a short-term forecast for future changes in the hydrologic regime and the dynamics of the Jingjiang–Dongting Lake relation.

Google Earth Engine‐Based Estimation of the Spatio‐Temporal Distribution of Suspended Sediment Concentrations in a Multi‐Channel River System of the Yangtze River Basin

“…The Songzi River has an intricated multi‐channel network system with two main branches diverging and rejoining across the plain (Sun & Shen, 2015). As one of the major diversions in the middle reaches of the Yangtze River, it exerts a significant impact on the evolution of the Yangtze River and Dongting lake (Chen et al., 2022; Ou et al., 2014). The average annual runoff at Xinjiangkou hydrological station on west branch of Songzi River (the main channel of the study area) from 2003 to 2020 is 249.32 × 10 8 m 3 , the average annual sediment transport is 368.85 × 10 4 t, and the average river width is 328 m. The average annual runoff at Shadaoguan hydrological station on the east branch is 56.49 × 10 8 m 3 , the average annual sediment transport is 107 × 10 4 t, and the average river width is 168 m (runoff and sediment transport data source from Yangtze River Sediment Bulletin).…”

“…Songzi River, connecting Yangtze River and Dongting Lake, is one of the most important outlets in the Jingjiang River (Zhang et al., 2015). Affected by the construction of the Three Gorges Dam (TGD), the sediment load in the downstream has been abruptly reduced, and the sediment load in the diversion channel drastically decreased (Chen et al., 2022; Zhang et al., 2015). In this study, the spatial and temporal patterns of the SSC in the upper reaches of the Songzi River were estimated based on the GEE cloud computing platform.…”

Coupling Machine Learning Into Hydrodynamic Models to Improve River Modeling With Complex Boundary Conditions

“…Considering the mainstream of the Yangtze River partially drains to Dongting Lake through three distributary mouths (i.e., Songzi, Taiping, and Ouchi) (Figure 1), the empirical formula and parameters (B. Chen et al, 2021; were used to calculate the streamflow of these three rivers (Text S2 in Supporting Information S1). Channel roughness was calibrated using a formula suitable for the Yangtze River (Gupta et al, 2009;Nash & Sutcliffe, 1970).…”