基于基尼系数的水文年内分配均匀度变异分析方法——以东江流域龙川站径流序列为例

Variation analysis method for hydrologic annual distribution homogeneity based on Gini coefficient.A case study of runoff series at Longchun station in Dongjiang river basin

由于受气候变化、人类活动及流域下垫面变化等因素的影响,许多水文要素序列不仅在年际形式上发生了变异,而且其年内分配特性也发生了不同程度的变异,严重影响了水利工程的规划设计以及水资源可持续利用和优化调配。目前有关水文要素年内分配特性的研究,多集中在分析水文要素年内分配的不均匀性上,很少涉及这种不均匀性是否随环境变化而发生变异,且有些不均匀性指标表达不直观、可比性不强,为此本文提出了基于基尼系数的水文年内分配均匀度变异分析方法。该法首先借用基尼系数构建水文要素年内分配均匀度模型,然后采用水文变异诊断系统分析年内分配均匀度序列的变异规律,最后利用均值差异法对其变异的物理成因进行分析。以东江流域龙川站多年逐月径流量序列为例,计算结果显示:龙川站径流年内分配均匀度GI在1973年发生了跳跃强变异,变异前后GI的均值相对增加了21.07%;这种变异约60%是由于人类活动特别是枫树坝水库的修建运行造成的下垫面变化引起的,而气候变化只占到约40%。

Due to climate change,human activities and changes in watershed land surface and other factors,many hydrologic series not only present inter-annual variation,but their annual distribution features also vary in different degrees.This has a strong impact on hydraulic engineering plan and sustainable utilization and optimized allocation of water resources.At present,most studies on the annual distribution of hydrologic elements focus on their inhomogeneity and rarely consider the factor of environmental change that impacts the inhomogeneity.And some inhomogeneity indicators are poor in intuitiveness or comparability.This paper puts forth an analysis method for variation of such homogeneity based on the Gini coefficient.First,this method uses the Gini coefficient to construct a model to describe the homogeneity,and then adopts a hydrologic variation diagnosis system to analyze the variation of the homogeneity GI series,finally uses a mean difference method to explore the physical origin.In a case study of the monthly runoff series at Longchuan station in the Dongjiang basin,the calculations show that in 1973,this runoff GI series took a strong hop mutation with its mean value increased by 21.07%.Of that sudden increase,roughly 40% came from climatic change and the rest 60% was a consequence of the changes in watershed land surface caused by human activities,in particular the construction and operation of the Fengshuba reservoir.