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气候变化及人类活动导致水文变异,变异前后样本总体分布显著不同,即改变了当地生态系统的水文状况,打破生态平衡。本文使用滑动秩和检验(Mann-WhitneyU检验)分析水文变异,并对水文变异成因做了系统的分析。在此基础上,对变异前各月平均流量序列用线性矩法推求GEV分布参数,求出概率密度最大流量,并将其视为相应月河道内生态流量。本文用该法计算黄河干流7站各月河道内生态流量,即得河道内生态需水情况。分析表明,考虑水文变异的河道内生态需水计算方法是可行的;水文变异后,黄河流域干流各水文站满足生态需水的频率大大降低,汛期降低幅度比非汛期大;黄河生态系统水环境恶化的主要原因是人类活动。
Climate change and human activities lead to hydrological variation. The overall distribution of samples before and after the mutation is significantly different, which changes the hydrological conditions of the local ecosystem and breaks the ecological balance. In this paper, we use the sliding rank sum test (Mann-WhitneyU test) to analyze the hydrological variation and make a systematic analysis of the causes of hydrological variation. On this basis, the GEV distribution parameters are estimated by the linear moment method for the average flow sequence before each month of variation, and the maximum probability density flow rate is obtained, which is regarded as the ecological flow in the corresponding monthly river channel. This method is used to calculate the ecological flow in each channel of seven stations of Yellow River mainstream in each month, which means the ecological water demand in the river channel. The analysis shows that it is feasible to calculate the ecological water requirement in the river course considering hydrological variation. After hydrological variation, the hydrological stations in the Yellow River basin meet the requirements of ecological water demand greatly reduced, the flood season reduced more than the non-flood season; the Yellow River ecosystem water environment The main reason for the deterioration is human activity.