汾河流域上游基流特征及其影响因素

Characteristics of base flow in upstream of Fen River Basin and its influencing factors

针对汾河流域河川径流量、河川基流量急剧减少和流域内生态环境恶化严重的问题,根据汾河流域上游控制站兰村水文站实测径流量数据,对比了数字滤波法、时间步长法对汾河流域基流分割的适用性,分析了基流变化特征及主要影响因素,并应用随机森林算法对影响因素重要性进行了评价。结果表明:数字滤波法(α=0.925)适宜汾河流域基流分割,可以客观反映汾河流域基流情况;河川基流量在1956—2016年呈极显著下降趋势,在2008年之后有所缓解,突变发生在1981年和2008年;汾河流域上游基流年内分布呈典型双峰型结构,峰值流量从之前的8月转移至3月,2000—2009年平均基流量仅为1956—1959年的1/8;降水量减少对基流量减少的贡献率仅为9.96%,不考虑气温影响时人类活动对基流量减少的贡献率为83.19%;人类活动中煤矿开采和地下水开采是造成基流减少的主要因素。

In view of the sharp reduction of river runoff and river base flow in the Fenhe River Basin and the serious deterioration of ecological environment in the basin,according to the measured runoff data of Lancun hydrological station,the upstream control station of the Fenhe River Basin,the applicability of digital filter method and time step method to the base-flow separation in the Fenhe River Basin was compared.The variation characteristics and main influencing factors of base flow were analyzed,and the importance of influencing factors was evaluated by using random forest algorithm.The results show that the digital filter(α=0.925) is suitable for base-flow separation in the Fen River Basin and can objectively reflect the base flow situation in the Fen River Basin.The river base flow showed a very significant downward trend from 1956 to 2016,and eased after 2008.The mutation occurred in 1981 and 2008.The annual distribution of base flow in the upstream of Fenhe River Basin showed a typical bimodal structure.The peak flow shifted from August to March.The average base flow from 2000 to 2009 is only 10% of that from 1956 to 1959.The contribution rate of precipitation reduction to base flow reduction is only 9.96%.When the influence of temperature is not considered,the contribution rate of human activities to base flow reduction is 83.19%.In human activities,coal mining and overexploitation of groundwater are the main factors causing the reduction of base flow.