基于基流比例法的洋河干流生态基流估算

为了更好地反映高频率取用水影响下北方季节性河流的生态基流量需求,采用细化到月尺度的基流比例法,分析计算了洋河1956—2015年的年尺度及月尺度生态基流量以及2015年的日生态基流保障程度。结果表明:丰水年、平水年、枯水年和特枯年的平均生态基流分别为3.64 m3/s、2.70m3/s、2.00 m3/s和1.31 m3/s;逐年生态基流持续减少,由1980年前的5 m3/s左右锐减到近十年的1.5 m3/s左右。不同年型基流量的逐月分布情况存在一定差异性,特别在特枯年1月、7月、8月及12月生态基流并不能满足至少保留10%多年平均径流量的生态需求,并出现非汛期生态基流最大,汛期生态基流反而最小的异常现象。2015年,洋河干流的日生态基流保障率仅为51%。不同年型及不同时间尺度的计算结果均阐释了洋河生态环境明显退化的趋势和严峻的健康形势,而且月尺度结果更详尽、更能映射取用水破坏河流生态的关键性和显著性。因此,建议分析河流生态需水时应区分河流丰枯状况,并尽可能地细化时间尺度。

Basic flow ratio method-based estimation of ecological basic flow of main stream of Yanghe River

In order to reflect the demands of ecological basic flow from the northern seasonal rivers under high-frequency water intakes，the basic flow ratio method refined to the month-scale is adopted to analyze and calculate the year-scale and month-scale ecological basic flows from 1956 to 2015 of Yanghe River as well as the guarantee degree of the daily ecological basic flow in 2015. The result shows that the mean ecological basic flows of wet year，normal year，dry year and extreme dry year are 3. 64 m3 / s、2. 70 m3 / s、2. 00 m3 / sand 1. 31 m3 / s respectively，while the ecological basic flow continuously and sharply decreases year by year from about 5 m3 / s in 1980 to about 1. 5 m3 / s in the recent ten years. The differences exist among the monthly distributions of the basic flows in different year-types，especially the eco-demand of at least 10% of mean runoff cannot be met by the ecological basic flows in January，July，August and December during the extreme dry year，while the abnormal phenomena of that the largest of ecological flow is in non-flood season，instead，the smallest one is in flood season. In 2015，the guarantee rate of the daily ecological basic flow is only 51% . The significant degradation trend and severe health status of the eco-environment of Yanghe River are explained by all the calculation results from different year-types and different time-scales，moreover，the significant role of water intake and water use on the destruction of river ecological environment can be more detailedly reflected by the result from the month-scale. Therefore，it is suggested that the wet and dry statuses of the river must be distinguished when analyzing the eco-water demand of the river，furthermore，the time-scale must be refined as detail as possible.