Experimental study and application of energy-sediment relationships in regions of confluence with low-silt water

Subbasin of the Yangtze River Basin (Jialing River Basin). Confluence zones are crucial for understanding erosion and deposition influences on hydroecological environments. Few studies use energy theory for these processes. This research links suspended energy loss with sediment dynamics (erosion and deposition volumes) in confluence zones, using Jialing River field measurements and laboratory flume experiments. Downstream from the confluence, average cross-sectional velocity increases from 0.12 m/s to 0.21 m/s, then decreases to 0.14 m/s. The median particle diameter of suspended sediment rises from 7.98 μm to 10.46 μm before dropping to 7.54 μm. Analysis shows the energy-sediment relationship based on turbulent kinetic energy has low correlation (R²= 0.501), while suspended energy provides stronger representation (R²= 0.922). Jialing River Basin results confirm a robust linear correlation between suspended energy loss and net sediment volume changes (R²= 0.919). This correlation shows no significant association with upstream confluence number. The critical suspended energy loss for sediment balance is 0.27 × 10⁴ J; values above cause deposition and below cause erosion. This study lays the theoretical groundwork for enhanced riverbed morphological evolution models based on energy dynamics. • Established the energy sediment relationship in the river confluence area. • The energy loss threshold for sediment balance has been determined. • Insights for riverbed evolution models and sediment management strategies.