长江水文对长江河口段苏南沿岸区域钉螺影响的研究

Impact of hydrology on the spread of oncomelania to southern coast of Yangtze estuary in Jiangsu province

目的为了评估长江江滩钉螺能否通过长江水流扩散进入长江河口段苏南区域。方法开展长江流速和流向测定,潮位和涨潮速度观察;进行不同流速下钉螺从漂浮物上脱落试验;对白水滩高程测定,计算江水淹没芦苇滩天数。结果江阴鹅鼻嘴段的流速均在2m/s以上,钉螺在1.951m/s以上脱落比较明显;长江河口段苏南区域流速在1.9m/s以下;在最低潮位流速最大,长江水顺流而下,涨潮时流速减小,流向与与主流向形成夹角,直至成为反方向逆流;张家港闸观察点2007年度潮位最高值5.98m,平均2m以上,潮位差最大3.31m,平均2m以上;低潮位时,潮水在坡度0.0042～0.0014。江滩上的涨潮速度为25m/h,在高潮位时,潮水在坡度0.0085～0.0086。江滩上的涨潮速度为88m/h;全年高潮位超过白水滩淹没芦苇滩的时间330d,低潮位超过白水滩7d(其中淹到芦苇滩2d)。结论江阴鹅鼻嘴段的高速水流是长江下游拦截钉螺的天然屏障;潮水顶托可能将残存的钉螺卷入江水;持续的大水可能会成为上游钉螺进入长江苏州段的最大隐患。

Objective To assess whether the Marshland oneomelania could diffuse into south coast of the Yangtze River estuary section through water. Methods We determined the Yangtze River flow velocity and flow direction eontinuously,and collected detailed data of tide level and tide speed simultaneously;We also compared oncomelania falling off situation from float at different flow rate;Furthermore,the altitude beach of Baishui marshes was measured and the submerged days of the reed marshes was calculate throughout the year. Results The flow velocity analysis showed that the flow velocity in the Jiangyin E＇bizui section was over 2 m/s,which was significantly higher than that of downstream which was below 1.9 m/s,and it was worth noting that oncomelania falling off situation was well connected with flow velocity, specifically,oncomelania fell off obviously when the speed was 1.951m/s or above. The Yangtze River flow velocity was related to tide,simplely,whieh was fastest when reflux and reduced at high tide because they were in opposite directions. Historical data clearly demonstrated that the highest tidemark and tide level difference was 5.98m and 3.31m respectively, and both average was over 2m at Zhangjiagang brake observation point in 2007. Futhermore, the slowest and quickest rising tide on river beach was 25m/h and 88m/h. We also found an annual average of 330 days that the high tide beyond Baishui marshes and submerged the reed marshes,in eonlrast,there were only 7 days beyond Baishui marshes at low tide. Conclusions The high flow velocity at the Jiangyin E＇bizui section indeed acted as the natural barrier to intercept the oneomelania;Tide could effectually obstruct oncomelania spreading towards lower reaches of the Yangtze River through tide-topping effect;The effects of continuous flood may play as capital potential risk on the oncomelania distribution and spread to Suzhou section of the Yangtze River.