珠江河网横向汊道水位演变特性及原因探究

珠江河网横向汊道体系是维持三角洲河网动力平衡的独特地貌结构,具有泄洪纳潮的重要功能,探讨该结构水位的阶段性演变及其影响因子辨识是河口动力学研究的重要科学问题。采用流量驱动的R＿TIDE数据驱动模型,对研究区域内“容桂-凫洲水道”和“潭洲-前航道”两个典型横向汊道体系共8个站点的日均水位序列进行分解,分离出由上游流量驱动引起的水位变化及地形和海平面共同驱动的水位变化。结果表明,经过水库的调蓄作用,在“容桂-凫洲水道”,流量驱动导致冬季日均水位抬升(平均为0.04m),其余三季日均水位下降;“潭洲-前航道”则由于北江流量增大导致流量驱动的日均水位均有不同程度的抬升(平均为0.17 m)。由于地形下切和海平面上升,地形和海平面共同驱动的日均水位变化普遍为负值(除南沙、黄埔站分别为0.11、0.07 m),“容桂-凫洲水道”中下部河段在秋季受海平面上升(秋季海平面高程最大)影响大于河床地形下切效应导致水位抬升,而其余站点主要受到疏浚、采砂等人类活动引起的地形下降影响,水位下降,且上游变化幅度明显大于下游;对径潮动力方差贡献率的分析结果表明,“容桂-凫洲水道”和“潭洲-前航道”夏季径流对水位的方...

MECHANISM AND EVOLUTION OF WATER LEVEL CHANGES IN THE TRANSVERSE CHANNEL SYSTEM IN THE ZHUJIANG (PEARL) RIVER CHANNEL NETWORKS

As a unique geomorphic unit among the Zhujiang (Pearl) River Channel Networks, transverse channels are vital to balance water level via flood discharge and tidal storage. A data-driven model termed R_TIDE was adopted to identify changes in averaged water level daily recorded in eight tidal stations in two typical transverse channel systems (i.e., "Ronggui-Fuzhou Channel" and "Tanzhou-Front Channel"), from which two components of water level change were extracted that driven by river discharge observed at upstream hydrological gauge stations and the combined effects of landform and sea level fluctuation. Results show that for the first component, the gauged daily average water levels in "Ronggui-Fuzhou Channel" are mainly controlled by dam construction, leading to an increase of about 0.04 m on average in winter and a decrease in other seasons, while in "Tanzhou-Front Channel", water levels are affected by river discharge from the Beijiang River (a tributary to Zhujiang River), building up an increase of about 0.17 m on average. For the second component, water level decreases were observed in most of stations, except for Nansha and Huangpu stations where minor increase of 0.11 m and 0.07 m, respectively, was shown. Specifically, water level increase in the mid-lower reaches of "Ronggui-Fuzhou Channel" in autumn is mainly by the sea water level rise, showing greater effect than that of down cutting of riverbed. In the rest of the stations, water level decreases were observed, which could be explained by human activities such as channel dredging and sand mining, leading a much more considerable change at upstream reach than that at downstream reach. In addition, the variance contribution rate of riverine dynamics to water levels in "Ronggui-Fuzhou Channel" and "Tanzhou-Front Channel" decreased by 10% and 15% on average in summer, and by 5% and 3% in winter, respectively, showing a tendency of reduced pressure of flood discharge and increased tidal storage after intensive human interventions.