蓄水影响下三峡库区小流域径流变化情势分析

Analysis of the Hydrological Regime in Small Basins within the Three Gorges Reservoir Area During the Impoundment Period

水文变化是三峡工程带来的重要问题之一,关乎三峡库区水资源开发利用和生态可持续发展,现有研究多侧重蓄水对长江干流的径流影响,鲜有研究关注库区小流域径流变化问题。基于库区3个典型小流域(大宁河、澎溪河和磨刀溪)2003-2017年逐日水文资料,运用趋势分析、集中度和集中期等方法,从径流量和离散程度方面分析了径流多时间尺度变化特点,揭示了175 m蓄水前后(2003-2008、2009-2017年)的径流特征,探讨了径流变化情势的影响因素。结果表明:①大宁河和澎溪河流域年均径流量呈下降趋势,磨刀溪流域无明显变化,而月均径流量的变化差异较大,大宁河与澎溪河在汛期(7月)明显下降,磨刀溪在非汛期(2月)明显上升,径流极值主要表现为不显著下降;②各小流域的集中度和集中期分别呈不显著的下降和上升趋势;③蓄水后,各小流域径流集中期明显滞后于降水,径流年内分配趋于均匀,降水-径流相关性下降,月均径流相关系数下降了2%~6%,而年极值相关系数下降了3%~12%。研究成果可为三峡库区小流域水文水资源管理提供科学依据。

Hydrological regime is an important problem brought about by the Three Gorges Project and directly influences the development and utilization of water resources and ecological sustainable development in the Three Gorges Reservoir Area.Existing studies mainly focus on the influence of water storage on the main stream of the Yangtze River,with little attention to the runoff variations in small basins of the reservoir area.Based on the daily hydrological data of three typical small basins(Daning River,Pengxi River,and Modaoxi River)in this area from 2003 to 2017,by adopting the methods of trend analysis,runoff concentration degree,and runoff concentration period,the multi-time scale change characteristics of runoff are identified from the aspects of runoff and dispersion degree.Meanwhile,the runoff characteristics before and after 175 m water storage(2003-2008,2009-2017)are revealed,and the influencing factors of runoff variations are discussed.The results are as follows.①The average annual runoff of the Daning River Basin and Pengxi River Basin shows a downward trend,but there are no obvious variations in the Modaoxi River Basin.The monthly average runoff in the three basins varies greatly.The runoff of the Daning River Basin and Pengxi River Basin has a significant decrease in the flood season(July),while that of the Modaoxi River Basin has significant increases in the non-flood season(February),and the extreme value of runoff mainly shows a non-significant downward trend.②The runoff concentration degree and runoff concentration period of each basin show a non-significant decrease or increase respectively.③After water storage,the runoff concentration period of each basin obviously lags behind the precipitation,the annual runoff distribution tended to be uniform,and the precipitation-runoff correlation decreases.The correlation coefficient of monthly average runoff decreases about 2%~6%,while that of annual extreme value decreases about 3%~12%.The research results can provide a scientific basis for hydrological and water resources management in small basins in the Three Gorges Reservoir Area.