径流与潮汐对崇明岛南部近岸水位影响机制研究

Influence of surface runoff and tides on water level in the nearshore of south Chongming Island

长江口地区是我国经济与文化中心,潮汐与径流是影响该地区近岸水位的主要因子。结合分布于崇明岛南部三个近岸测点S1、S2、S4的水位与邻近的堡镇(S3)潮汐、大通水文站径流、宝山气象站平均风速与气温数据,运用互相关分析、相关分析、功率谱周期估计等方法,以定性与定量相结合的方式探究了潮汐、径流等因子对崇明岛南部近岸水位的影响。结果显示,近岸水位滞后于潮汐约2h;近岸水位与潮汐相关性明显,且经计算潮汐贡献率达90%以上。近岸水位去除潮汐后的水位余量形成于径流、气温与风的综合作用,径流与气温组合作用对S4水位余量影响占优,而风对S1水位余量影响占优。通过研究径流与潮汐等对崇明岛南部近岸水位影响机制,为合理选取感潮河段防洪设计水位提供参考,对长江口防洪减灾及咸潮入侵、海水倒灌对策研究等都具有重要意义。

Yangtze River Estuary is one of the centers of economy and culture in China,tides and runoff are the main factors influencing offshore water level changes. Three monitoring stations（ S1,S2,S4） in the south Chongming Island are established to measure offshore water level around one year in this area.Tides of Baozhen station,surface runoff of Datong station,average wind speed and temperature of Baoshan weather station are collected analyses. The impacts of tides,runoff,wind and temperature on offshore water levels in the three monitoring stations are explored by correlation analysis and power spectrum period estimation methods. Results indicate that the offshore water level lags behind tides about 2 hours,and it is mainly influenced by tides. Further calculations show that the contribution of tides on offshore water level changes is above 90%. Residues of offshore water level wiped off tides are closely related to temperature and wind speed. The periods of residues are controlled by surface runoff,temperature and wind speed.Combination of runoff and temperature is the main factor for the residue of station S4,which elevates the offshore water level. Wind speed is the leading factor for residue of S1,which reduces the offshore water level. Our study would be helpful to determine the rational water level in flood,and will be benefit flood and disaster control and taking reasonable measures to prevent saltwater intrusion.