Analysis of Water Level Fluctuations in Bifurcating Approach Channels Under the Flow Regulation of Reservoirs

AbstractAn approach channel is a restricted channel connecting the lock head with the upstream and downstream navigation waterway, characterized by a narrow navigation channel with a closed-end, small coefficient of cross-section, and low speed for vessel navigating. Due to the uncertain impact of the waves induced by the flow regulation of reservoirs on water-level fluctuations in bifurcating approach channels, the river reach between the Three Gorges Dam (TGD) and the Gezhouba Dam (GZD) is selected as the study area and the variations of water-level fluctuating amplitude in the approach channel located on the left bank downstream of the TGD are revealed under the joint regulation of the Three Gorges and Gezhouba reservoirs based on numerical simulations. Furthermore, the relationship between water level variation at the lower lock head of the ship lift and the flow regulation of reservoirs is investigated in detail. Results indicated that water level variation of the ship lift approach channel exhibits an amplifying effect and the lower lock head of the ship lift is a key concern for navigable flow conditions. In addition, the flow variation rate should be controlled within the range of 2,000 m3/15 min in the context of joint regulation of two reservoirs, which enables the safe docking of vessels at the lower lock head of the ship lift. The findings in this study may contribute to the designing and planning of the newly-planned Three Gorges ship lock approach.