渭河生态基流时空分异特征及保障率分析

以渭河为研究对象,依据渭河干流北道、林家村、魏家堡、咸阳、临潼、华县6个主要断面1971-2014年的水文实测资料,基于河流典型生态环境特征划分河流生态类型,并对其生态基流量进行优化计算,在此基础上揭示渭河生态基流时空分异特征及生态基流保障率。结果表明:选取北道、林家村、魏家堡、咸阳、临潼、华县断面枯水期的最小值作为相应断面的生态基流量推荐值,分别为5. 68、2. 51、11. 39、25. 33、77. 26和61. 86 m3/s;从时间变化看,各断面生态基流年内最大值均集中在汛期(7-9月),最小值集中在枯水期(12-次年3月)。除汛期外,各断面的生态基流月均值变化轨迹整体一致,各断面生态基流除8月与1、2、3、4、6、10、11、12月差异不显著(P>0. 05)外,其余各月两两之间差异均显著(P <0. 05);从空间分布来看,林家村断面1月生态基流量最小,华县断面8月生态基流量最大,体现出渭河上游生态基流量不足而下游河道泥沙淤积的生态环境特征;生态基流量总体上呈上游低下游高的特征,除魏家堡和华县断面月均生态基流量差异不显著(P> 0. 05)外,其余各断面之间差异均显著(P <0. 05)。

Spatio-temporal differentiation characteristics and guarantee rate of the environmental flow in Weihe River

Taking Weihe River as the research object, based on the hydrological survey data of six main sections which are Beidao,Linjiacun,Weijiabao, Xianyang, Lintong and Huaxian of the Weihe River mainstream from 1971 to 2014, we classified the ecological types and calculated the optimal environmental flows (e-flows) of the sections according to their respective environmental characteristics. On this basis, the spatio-temporal differentiation characteristics and guarantee rate of e-flow in Weihe River are revealed. According to the results, the minimum runoff values of the sections are recommened as their e-flows which are 5.68 m³/s, 2.51 m³/s, 11.39 m³/s, 25.33 m³/s, 77.26 m³/s and 61.86 m³/s respectively for Beidao, Linjiacun, Weijiabao, Xianyang, Lintong and Huaxian sections during dry season. The maximum value of e-flow of each section occurs in the flood season (from July to September), and the minimum value in the dry season (from December to March). Except for the flood season, monthly average of e-flow in each section is consistent as a whole. The e-flows of the six sections have no significant difference (P>0.05) between August and January, February, March, April, June, October, November and December, but there is a significant difference between any other two months (P<0.05). Spatially, the e-flow of Linjiacun section in January is the smallest and Huaxian section in August is the largest, which reflects the environmental characteristics of insufficient e-flow in the upstream and sediment deposition in the downstream of Weihe River. The e-flow is generally low in the upstream and high in the downstream. There is no significant difference in monthly e-flow (P>0.05) in Weijiabao and Huaxian; however the differences among the other sections are significant (P<0.05).