As a coupling river system, watershed management in sediment source areas may influence downstream reach. However, the connectivity between water and sediment retention (WSR) in two coarse sediment source areas (tributaries entering the Inner Mongolia Reach, IMR, and tributaries entering the Middle Yellow River, MYR) and deposition in the Lower Yellow River (LYR) have rarely been compared. Experiential fitted models for each river segment (IMR, MYR, and LYR) are loosely linked to investigate the coupling relationship between source areas and deposition area. Analysis shows that, at the zonal scale, the connectivity between WSR in different zones and deposition reduction in different river reaches differs. WSR in tributaries of the IMR may benefit the local channel (IMR) with a priority ratio, and WSR in the stem channel of the IMR may benefit both the local (IMR) and the lower (LYR) channels with almost the same magnitude. WSR in the MYR may benefit the local channel (LT reach) and the lower channel (LYR), while the LYR has more propriety. At the zonal scale, the temporal scales over which changes in hillslopes occur also differ, as WSR in the IMY and MYR during the non-flood season may also contribute to deposition reduction in the MYR and LYR. In total, the loosely linked model may provide information of sediment along the whole river network.