长江下游九江–大通河段水面比降变化特征分析

Analysis of Surface Slope in Jiujiang-Datong Reach of the Lower Yangtze River

摘要: 基于长江下游干流九江–大通河段历史日均水面比降，辨识该河段水面比降的变化趋势和突变点，分析突变前后水面比降的变化特征及影响因子。结果表明：1) 1957~2023年，九江–大通河段全年、汛期、非汛期平均水面比降下降趋势显著。水面比降近似呈现单峰特征，汛期较大，非汛期较小，7月左右达到峰值；2) 全年、汛期、非汛期平均水面比降均于2003~2005年间发生了突变。三峡蓄水后水面比降较蓄水前整体有所下降，其中：月最大除6月份微增2.0%外，其余月份降低0.2%~12.9%；月最小除1月~4月微增1.9%~5.2%外，其余月份降低0.2%~20.8%，月平均较蓄水前降低0.1%~12.4%；3) 蓄水前后，水面比降与上下游流量关系有所改变，蓄水后高水与低水的水面比降差异明显高于蓄水前，可认为水库调度对下游水文、河道产生了一定影响。

Abstract: Based on the surface slope data of Jiujiang-Datong reach of the lower Yangtze River, the trend and change point of surface slope were extracted, and the change characteristics and influence factors before and after the change point were analysed. The results indicate that: 1) From 1957 to 2023, the average slope data of Jiujiang-Datong reach showed a significant downward trend throughout the year, flood season, and non flood season. The surface slope is relatively larger during the flood season and smaller during the non flood season, reaching its peak around July; 2) The surface slope experienced a sudden change throughout the year, flood season, and non flood season in 2003 to 2005. Since the operation of the TGD, the surface slope has decreased, with the maximum monthly surface slope decreased by 0.2%~12.9% except for a slight increase of 2.0% in June; except for a slight increase of 1.9%~5.2% from January to April, the monthly minimum surface slope decreased by 0.2%~20.8% in other months, and the monthly average surface slope decreased by 0.1%~12.4%; 3) The relationship between surface slope and flow has changed before and after the operation of the TGD. The difference in surface slope between high and low water levels has significantly increased after the operation of the TGD. It can be considered that the reservoirs scheduling has a certain impact on the downstream hydrology and waterway.