气候和土地利用变化对石羊河流域自然径流的影响

Climate and Land Use Change Effect on Natural Runoff in Shiyang River Basin

气候变暖及人类活动对石羊河流域地表径流时空特征产生了显著影响,流域水资源适应性管理面临严峻挑战。以石羊河流域三个独立的子水系大靖河水系、六河水系和西大河水系为研究对象,采用统计方法分析1960-2020年石羊河流域各子水系年平均径流量演变规律,利用Mann-Kendall检验、Pettitt检验等方法确定径流序列突变点,设计气候和土地利用变化的组合情景,结合验证后的SWAT模型定量辨识石羊河流域径流变化归因,以期解决水资源配置不均等问题。结果表明:(1)1960-2020年石羊河流域大靖河水系、六河水系、西大河水系年平均径流量下降速率分别为0.01m^(3)·s^(-1)、0.07m^(3)·s^(-1)和0.01m^(3)·s^(-1);1960-2020年六河水系、西大河水系径流量突变年分别为1973年和2002年,大靖河水系尚无径流量的突变,仍处于自然状态。(2)SWAT模型对石羊河流域有较好的适应性,经率定和验证,模型的决定系数和纳什效率系数均高于0.50。(3)1960-2020年六河水系年平均降水量、平均气温、相对湿度、太阳辐射和平均风速的变化对年平均径流量减少的贡献率分别为75%、53%、55%、55%和52%,土地利用变化对年平均径流量减少的贡献率为17%;综合6个影响因子耦合作用对年平均径流量减少的贡献率为67%,气候变化对石羊河流域径流影响较大。

Climate warming and human activities have a major impact on the spatial and temporal characteristics of surface runoff in the Shiyang river basin,and the adaptive management of water resources in the basin is facing serious challenges.With three independent drainage Dajinghe river system,Liuhe river system and Xidahe river system as the research object,the statistical method analyzed the average flow evolution in 1960-2020,using Mann-Kendall test and Pettitt test to determine the runoff sequence mutation point,set the combination of climate and land use change,and used SWAT model to identify the runoff variation in Shiyang river basin,addressing the unequal allocation of water resources.The results showed that:(1)from 1960 to 2020,the annual average runoff decline rate of Xidahe river,Liuhe river and Dajing river system was 0.01m3·s^(-1),0.07m^(3)·s^(-1),0.01m^(3)·s^(-1)respectively.The runoff years for the Liuhe river and Xidahe river were in 1973 and 2002,respectively,while the Dajing river system was in its natural state.(2)The SWAT model had a good adaptability to the Shiyang river basin,and the determination coefficient and the Nash efficiency coefficient were both higher than 0.50.(3)From 1960 to 2020,the contribution of precipitation,average temperature,relative humidity,solar radiation and average wind speed to the annual average runoff were 75%,53%,55%,55%,and 52%,respectively.The contribution of land use change to the annual average runoff was 17%.The coupled contribution of six influence factors to annual average runoff reduction was 67%,indicating that climate change had great influence on runoff in Shiyang river basin.The research results could provide a reference for the adaptive management of watershed water resources.