基于二元水循环模拟的密云水库上游流域河川径流演变归因分析

Attribution analysis of river runoff variation in the upper basin of Miyun Reservoir based on dualistic water cycle simulation

密云水库上游流域是首都重要的生态屏障和水资源保护地,近60 a来,流域河川径流量衰减明显,定量识别不同时期径流变化成因对于科学认识流域水循环演变机理具有重要意义。基于此,构建了二元分布式水文模型,设置了多个情景对流域水循环过程进行模拟,并在此基础上使用多因素归因分析法对河川径流演变进行了定量归因。结果表明:(1)近60 a来,人类活动对径流衰减的贡献(42.8%)略小于气候变化(57.2%),气候变化对径流的影响先减小后增大,而人类活动的影响先增大后减小;(2)从基准期(1960—1970年)到变化期(1985—1995年),气候变化使径流增加0.29亿m^(3),人类活动造成径流减少1.22亿m^(3),其中,人工林面积的大幅增加是径流减少的主要原因,从变化期(1985—1995年)到现状期(2007—2017年),气候变化与人类活动对径流衰减的贡献率分别为92.5%、7.5%,降水偏枯及年内分配变化是气候变化导致径流衰减的主要原因;(3)从基准期到变化期,多因素变化协同率为-61.6%,从变化期到现状期,为-92.7%,说明近60 a来多因素对径流的综合效应表现为负效应,且各因素对径流的影响抵消程度逐渐变小。

The upper basin of Miyun Reservoir is an important ecological barrier and water resources protection area in the capital.In the past 60 years,the runoff of the river basin has declined significantly.Quantitative identification of the causes of runoff changes in different periods is of great significance for scientific understanding of the evolution mechanism of water cycle in the basin.Based on this,a dualistic distributed hydrological model is constructed,and multiple scenarios are set to simulate the water cycle process of the basin.Accorading to the results of simulation,the multi factor attribution analysis method is used to quantitatively attribute the river runoff evolution.The results show that:(1)In recent 60 years,the contribution of human activities to runoff attenuation(42.8%)is slightly less than climate change(57.2%),and the impact of climate change on runoff first decreases and then increases,however,the impact of human activities first increases and then decreases.(2)From the base period(1960—1970)to the change period(1985—1995),climate change increases runoff by 29 million m^(3),and human activities decrease runoff by 122 million m^(3).From the change period(1985—1995)to the current period(2007—2017),the contribution rates of climate change and human activities to runoff attenuation are 92.5%and 7.5%respectively,and the main reasons of runoff attenuation caused by climate change are dry precipitation and it′s changes of annual distribution.(3)From the base period to the change period,the synergetic rate of multi factor change is-61.6%,while from the change period to the current situation period,it is-92.7%,which indicates that the comprehensive effect of multiple factors is negative in recent 60 years,and the offsetting degree of each factor on runoff gradually decreases.