Abstract. The construction of large reservoirs results in the formation of tributary bays, and tributary bays are inevitably influenced by backwater
jacking and intrusions from the main reservoir. In this paper, a typical
tributary bay (Tangxi River) of the Three Gorges Reservoir (TGR) was
selected to study the hydrodynamic and environmental characteristics of a
tributary bay influenced by the jacking and intrusions from the main
reservoir. The flow field, water temperature, and water quality of Tangxi
River were simulated using the hydrodynamic and water quality model
CE-QUAL-W2 (thomas and Scott, 2008), and the eutrophication status of the tributary bay was also evaluated. The results showed that the main reservoir had different effects
on its tributary bay in each month. The tributary bay was mainly affected by
backwater jacking from the main reservoir when the water level of the main
reservoir dropped and by intrusions from the main reservoir when the water
level of the main reservoir rose. An obvious water quality concentration
boundary existed in the tributary bay, which was consistent with the
regional boundary in the flow field. The flow field and water quality on
both sides of the boundary were quite different. The results of this study
can help us figure out how the backwater jacking and intrusions from the
main reservoir influence the hydrodynamic and water environment
characteristics of the tributary bay and provide guidance for water
environment protection in tributary bays.