闽江下游水文情势演变及其对压咸流量保证率的影响

Evolution of Hydrological Regime and Its Impact on the Guaranteed Rate of Saltwater Intrusion Suppression Flows in the Lower Reaches of the Minjiang River

针对近年来闽江下游河口自然水文情势发生变化致使咸潮上溯现象逐渐加剧的问题,选取闽江下游竹岐站1950~2018年逐日流量资料,采用Mann-Kendall法进行趋势和突变检验,确定1997年为径流突变年份。采用水文指标变化范围法(IHA/RVA)对突变前后两个时间序列1950~1996、1997~2018年的32个水文指标进行分析。结果发现除了低流量脉冲发生次数及历时和逆转次数为高度改变,其余指标均为中、低度改变,闽江下游水文整体改变度为38.16%,为中度改变。采用两种压咸流量方案对两个时间序列代表年进行保证率分析,其中方案1压咸流量过程的最小值及总需水量较方案2少,压咸流量保证率高。压咸流量保证率突变后较突变前整体增加,尤其是在枯水年,压咸流量保证率大幅增加,但同时存在丰水年压咸流量保证率下降的问题。说明水库的投入运行影响下游径流过程,可以改善枯水期下游河口地区咸潮入侵问题,但也使丰平枯各年的压咸流量保证率趋于一致。

Responding to the changes of the natural hydrological regime of the lower reaches estuary of the Minjiang River in recent years,resulting in a gradual increase in the phenomenon of upward salty tides,this paper selected the daily flow data from 1950 to 2018 at Zhuqi station in the lower reaches of the Minjiang River,and used Mann-Kendall method to analyze the trend and sudden change.The mutation year appeared in 1997.The range of variation of hydrological indicators method(IHA/RVA)was used to analyze 32 hydrological indicators for two time series before and after the mutation,1950-1996 and 1997-2018.All the indicators are moderate and low,except for the number of low-flow pulse occurrences and duration and the number of reversals,which are highly altered.The overall hydrological alteration of the lower reaches of the Minjiang River is 38.16%,which is moderate.The guarantee rate analysis for two time series representative years at two saltwater intrusion suppression flow scenarios was carried out.The minimum and total water demand of saltwater intrusion suppression flow process in scheme 1 is less than in scheme 2,and the guaranteed rate of saltwater intrusion suppression flow is higher.The guaranteed rate of saltwater intrusion suppression flow increases overall after the mutation compared with that before the mutation.Especially in the dry year,the guaranteed rate of saltwater intrusion suppression flow increases substantially,but at the same time there is the problem of decreasing the guaranteed rate of saltwater intrusion suppression flow in the high flow year.It shows that the operation of the reservoir affects the downstream runoff process,but it also makes the guaranteed rate of saltwater intrusion suppression flow rate in high flow year,normal flow year and low flow year converge.