大通水文站流量演变及其旱涝特征分析

Analysis of Streamflow Change and Its Drought-flood Characteristics at Datong Station of Yangtze River

在变化环境和上游水库调蓄影响下,分析长江中下游地区流量的演变规律和旱涝特征,对江苏省防洪安全和水资源利用至关重要。为定量评估长江中下游近50年来流量演变规律和旱涝变化特征,基于大通水文站1971~2020年逐月流量实测数据,采用Mann-Kendall检验、Morlet小波分析等方法综合分析大通站流量变化趋势、突变性、周期性和年内分布规律,并计算标准化流量指数分析其旱涝特征。结果表明,近50年来,大通水文站年均流量具有非显著增加趋势,年际变化较为稳定,但在2003年存在显著突变,突变后显著增加;年均流量序列主要存在12年的周期,且主要集中在1995年之前,具有3次丰枯交替震荡;大通站流量年内分配不均,主要集中在汛期,7、8月流量最大,但汛期各月流量序列变化不显著,而枯季各月如12月至次年3月流量具有显著增加趋势;不同时间尺度标准化降水指数反映干湿变化较为一致,2003年后干旱发生几率较高,年干旱发生频率为44.4%,而洪涝发生几率由37.5%减少到16.7%,发生率明显降低。从季节上看,2003年秋季和夏季干旱发生率偏高,而春季和冬季发生率明显降低。对各季标准化降水指数进行MK趋势检验可知,除在秋季减少外,其他各季增加,尤其是冬季增加趋势显著。

Under the influence of changing environment and upstream reservoir regulation and storage,it is very important for the safety of flood control and the utilization of water resources in Jiangsu Province to analyze the evolution law of flow and the characteristics of drought and flood in the middle and lower reaches of Yangtze River.The trend,change point,period and annual distribution characteristics of streamflow at Datong station in Yangtze River from 1971 to 2020 were investigated by using the Mann-Kendall test and Morlet wavelet transform.Meanwhile,the characteristics of droughts and floods was analyzed using standardized streamflow index(S_(SI)).The results show that the annual average streamflow of Datong hydrological station has shown a non-significant increasing trend,with relatively stable inter-annual changes in the past 50 years.However,there is a sudden change point in 2003,with a significant increase after the mutation;The annual average flow series mainly has a period of 12 years and is mainly occurred before the year of 1995,with three alternating oscillations between high and low flow;The annual distribution of streamflow at Datong station is uneven,mainly concentrated in the flood season,with the highest flow in July and August.However,the flow sequence changes in each month of the flood season are not significant,while the monthly flow in the dry season,such as from December to March of the following year,shows a significant increasing trend;The S_(SI) index at different time scales reflects relatively consistent changes in drought and flood conditions.After 2003,the probability of droughts was higher with an annual drought frequency of 44.4%;While the probability of floods decreased from 37.5%to 16.7%.From a seasonal perspective,the incidence of drought in autumn and summer was relatively high,while the incidence in spring and winter decreased.According to the MK trend test of the S_(SI3),it decreased in Autumn,but its increased in other seasons,especially in winter.