The spatio-temporal evolution of backwater influence length in estuaries is essential with regard to the sustainable water resources management in general, such as flood control, water supply, and shipping. In this study, based on the classical riverine backwater theory, we focus on the backwater effect caused by tidal dynamics, making use of a one-dimensional hydrodynamic analytical model to redefine the upstream boundary of the backwater zone (namely backwater limit) in estuaries. The model was subsequently applied to the Changjiang River Estuary to explore the evolution of estuarine backwater dynamics and its underlying mechanism. Results show that the distance from Tianshenggang to backwater limit (i.e., the backwater influence length) has a negatively linear correlation with the upstream river discharge and positively linear correlation with the tidal amplitude of seaward boundary, respectively. The response of the backwater limit to tidal river dynamics is more sensitive than that of the tidal limit, which can effectively characterize the evolution of the tidal river dynamics in tidal reach. The location of the backwater limit in the Changjiang River Estuary has apparent seasonal difference, being 419 km away from Tianshenggang during the spring and 367 km during autumn. The location is situated above the tidal reach during the winter, while the backwater effect caused by tidal dynamics during the summer is negligible. It was shown that the seasonal variations of residual water level slope induced by tide and tide-river interaction are the dominant factors for controlling the location of the backwater limit in the Changjiang River Estuary.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |