Human impact on the river channel changes downstream Changzhou hydro-junction in Xijiang river of China

Zhang Ming, Feng xiaoxiang

Tuesday 30 june 2015

17:42 - 17:45h at Oceania (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) River morphodynamics, Poster pitches

Parallel session: Poster pitches: 7B. Sediment - River

Dam imposes changes of flow and sediment transfer, and due to the clear water release and unsteady flow of dam operation, the downstream channel bed tends to erode. The degradation process may be greatly aggravated by the human impacts including river sand mining and channel restoration project, which probably produces a big fall of low water level. When the changes are beyond estimate, the safety of waterway navigation is likely to be threatened by the variation of low water level, because the water depth at the ship-lock is not enough for the design ship draft, especially these changes occurs in the near-dam reach downstream hydro-junction. Changzhou hydro-junction, a low head hydro-electric station located on the downstream of Xijiang river in Guangxi province of china, serves to provide power generation, navigation, and flood control. It is famous in china for the world’s largest river ship-lock having four-parallel lock chambers, however , the first double lock chambers completion in the year 2007 have been facing the navigation crisis caused by the fall of low water level, and the last double lock chambers went into construction two year later. Based on the field topographical and hydrological data, this paper analyzed the variations of river bed and low water level, furthermore, studied the channel responses to multi-factors dominated by human impact. The results show that: During the early years of Changzhou dam impoundment form 2007~2012, the low water level under the same discharge has been largely fallen resulting from the integrated factors of dam operation, extensive mining and channel restoration, and the last two was the main factors in currently fall of the low water level. These results are useful for channel regulation as a valuable reference.