2011年春末夏初枯水期间长江河口盐水入侵

Saltwater intrusion in the Changjiang River Estuary during the drought in late the spring and early summer of 2011

全球气候变化导致的长江流域枯水事件近几年趋于增多．2011年春末夏初长江中下游发生干旱，4、5和6月大通径流量分别比多年月平均值分别下降了33。4％、50．6％和50．3％．观测资料表明，4月崇西水文站大部分时间盐度大于0．45（饮用水标准），北支倒灌盐水从崇西水文站到南门大约需要2d，到宝钢水库需要3～5d，宝钢水库出现2d和4d不宜取水时间，青草沙水库出现5d和4d不宜取水时间．5月中下旬北支永隆沙仍被高盐水占据，崇西水文站盐度超标达到7d，青草沙水库不宜取水d数达到8d．6月4—7日大潮后中潮期5个观测潮周期内东风西沙水库约有一半时间盐度大于0．45，陈行水库和青草沙水库取水口盐水均低于0．45，但随时间逐渐升高，盐份主要来源于北支倒灌．长江河口盐水入侵一般发生在12月和来年的1—3月，4—6月随着径流量的增大盐水入侵消失．气候变化产生的枯水事件加剧了长江河口盐水入侵、严重影响了非盐水入侵期水源地取水安全．

The drought events happen in the Changjiang River basin with increasing frequency in recent years due to the global climate change. There was a drought event at the middle and lower reaches of the Chang.iang River in the late spring and early summer of 2011, resulting in the riv er discharge at Datong station in April, May and June of 2011 decrease 33. 4%, 50. 6% and 50.3%, respectively, compared with the corresponding monthly mean values. The observation data indicated that in the April salinity at Chongxi hydrological station exceeded 0.45 （standard of drink water） in the most measured time, the saltwater spilling over from the North Branch took about 2 days and 3-5 days from Chongxi hydrological station to Nanmen and Baogang res- ervoir, respectively, the not suitable water intake time was 2 and 4 days at Baogang reservoir, 5 and 4 days at Qingcaosha reservoir. In the middle and late May, it was still occurred by high sa- line water at Yongtongsha in the North Branch, water standard at Chongxi hydrological station, it reached 7 days that salinity exceeded the drink the not suitable water intake time was 8 days atQingcaosha reservoir. During the observed 5 tidal periods from 4 to 7 in June （middle tide after spring tide）, salinity near Dongfenxisha reservoir water intake was higher than 0. 45 in about half observation time, was lower than 0. 45 near Chenhang reservoir and Qingcaosha reservoir water intakes, but increased gradually with time, indicating that the salt there come from the saltwater spilled over from the North Branch. The saltwater intrusion in the Chnagjiang River Estuary happens generally in December and next January to March, and vanishes in April to June with the increasing river discharge. The drought event induced by climate change enhanced the saltwater intrusion and influenced severely the safety of water intake in the Changjiang River es- tuary in the not period of saltwater intrusion.