Water Residence Time in a Typical Tributary Bay of the Three Gorges Reservoir

Abstract

Tributary bays of the Three Gorges Reservoir (TGR) are suffering from environmental problems, e.g., eutrophication and algae bloom, which could be related to the limited water exchange capacity of the tributary bays. To understand and quantify the water exchange capacity of a tributary bay, this study investigated the water residence time (RT) in a typical tributary bay of TGR, i.e., the Zhuyi Bay (ZB), using numerical simulation and the adjoint method to obtain the RT. The results show that RT of ZB with an annual mean of 16.7 days increases from the bay mouth to the bay top where the maximum can reach 50 days. There is a significant seasonal variation in RT, with higher RT (average 20 days) in spring and autumn and lower RT (average < 5 days) in the summer. The sensitivity experiments show that the TGR water level regulation has a strong influence on RT. The increase in the water level could increase RT of ZB to some extent. Density currents induced by the temperature difference between the mainstream and tributaries play an important role in the water exchange of ZB, while the impacts of the river discharges and winds on RT are insignificant.

Residence Time Analysis in the Albufera of Valencia, a Mediterranean Coastal Lagoon, Spain

“…The problem of poor water quality in the lagoon due to lack of renewal has also been detected in other places, such as the work of Cheng et al [38] where poor quality areas in coves of the Three Gorges Reservoir are related to high renewal times of up to 50 days, while good quality areas have values of less than 5 days.…”

Performance of ensemble‐learning models for predicting eutrophication in Zhuyi Bay, Three Gorges Reservoir

“…The drainage basin of the ZR is located between 109°01′ to 109°45′ E and 30°29′ to 31°22′ N, an area of about 153.6 km 2 and a length of 31.4 km. The average annual discharge of the ZR is 2.54 m 3 /s (Cheng et al, 2019). Owing to the impoundment of the TGR, Zhuyi Bay (ZB) was formed over a length of 6 km (Figure 1).…”

“…Owing to the impoundment of the TGR, Zhuyi Bay (ZB) was formed over a length of 6 km (Figure 1). The area of ZB is not strongly influenced by wind (annual mean wind speed: 1.5 m/s) but is sensitive to changes in hydrology and water quality in the main stream of the Yangtze River, which suffers from eutrophication (Cheng et al, 2019).…”

Tracers and Timescales: Tools for Distilling and Simplifying Complex Fluid Mechanical Problems

“…Cheng et al [22] compute the three-dimensional, time-dependent residence time in a typical tributary bay of the reservoir of Three Gorges Dam (China). They adopt the adjoint approach of Delhez et al [23] and perform a detailed sensitivity analysis aimed at identifying the processes that have the largest impact on the exchanges of the domain of interest with its environment.…”