考虑水文变异的大通河生态需水研究

Study on Ecological Flow of Datong River under Consideration of Hydrological Alteration

鉴于变化环境对流域水文情势的影响,开展水文变异条件下的生态需水研究尤为紧迫。以大通河流域为研究对象,采用水文变异诊断系统对变异前后的水文序列进行划分,分析变异成因;应用5种概率分布函数拟合变异前月均流量序列,推求概率密度最大处流量,将其作为当月生态需水;最后计算生态需水满足率,分析水文变异对生态需水的影响。研究表明:(1)尕大滩站在1973年、1990年发生弱变异;天堂站、享堂站在1990年发生中变异;(2)变异后,汛期生态需水满足率相比变异前平均下降7%,非汛期生态需水满足率相比变异前平均上升11%;(3)降水减少导致汛期生态需水满足率下降,冻土退化促使非汛期生态需水满足率上升;水利工程建设导致汛期生态需水满足率下降,非汛期生态需水满足率上升。研究结果可为大通河流域水资源开发利用和生态保护提供重要参考。

It is of great significance to carry out researches on ecological water demand with considerations of hydrological alterations, due to the effect of changing environment on hydrological status in basin. Taking Datong River as the study object, this paper employed the hydrological alteration diagnosis system to divide hydrological series, and analyzed the causations of hydrological alteration. Then, five kinds of probability distribution function were utilized to fit monthly average flow for each month before the occurrence of hydrological alteration. The monthly runoff corresponding to the maximum probability density was taken as the ecological water demand of that month. Finally, the effect of hydrological variation on ecological demand was analyzed by calculating the satisfaction rate of ecological water requirement(SREWR). The results show that(1) The weak hydrological alterations of Gadatan station occurred in 1973 and 1990 while the medium hydrological alterations of Tiantang and Xiangtang stations occurred in 1990;(2) After hydrological alteration, the SREWR in flood season decreases by 7% than before, the SREWR in dry season increases by 11% than before;(3) The decreased precipitation leads to the reduction of the SREWR in flood season,and the permafrost degradation results in the improvement of the SREWR in dry season. Moreover, the construction of water conservancy could decrease the SREWR in flood season and improve the SREWR in the dry season. The result could provide an important reference for the water resources utilization and ecological protection in Datong River basin.