基于改进年内展布法的河流生态流量研究

Study on River Ecological Flow Based on Improved Annual Distribution Method

为了使年内展布法更合理的计算季节性河流的生态流量,对原年内展布法进行了改进。以松花江支流西北河为例,基于西北河水文站1956-2016年逐月径流量资料,以90%保证率下各月的径流量代替各月最小径流量,并依据季节、丰枯月份、径流量3种标准分别划分时段,从而计算各划分标准下各时段的同期均值比,结合各月多年平均径流量进而对其生态流量进行计算,得到3种标准下最好的改进方法,使其与原年内展布法进行对比分析,并用Tennant法以及逐月最小径流法和90%保证率法对其结果验证。结果表明,3种标准下计算得出的生态流量与原年内展布法计算得出的生态流量年内变化趋势基本一致,其总体趋势为:改进方法一(按季节划分)>改进方法三(按径流量划分)>原年内展布法>改进方法二(按丰枯月份划分);与Tennant法及其他水文学方法(逐月最小径流法、90%保证率法)进行对比,改进方法一计算的生态流量较原年内展布法有了较好的改善,其既能够满足鱼类繁衍生存的需求和河流生物生长的需要,又能够保障河流的基本生态功能,因此对年内展布法的改进是合理可行的。综合来看,用改进方法一改进的年内展布法计算生态流量,更能体现河流的变化特征,更符合北方季节性河流生态流量的计算,更适用于西北河生态流量的计算,可以作为河流生态流量研究的一个新思路。

In order to make the annual distribution method more reasonable to calculate the ecological discharge of seasonal rivers,the original annual distribution method was improved.Taking the Northwest River,a tributary of the Songhua River,as an example,based on the monthly runoff data of the Northwest River hydrological station from 1956 to 2016,the monthly runoff at 90% guarantee rate was used to replace the monthly minimum runoff,and the period was divided according to the three criteria of season,abundant and dry months,and runoff,so as to calculate the mean ratio of each period under each partition criteria.The ecological flow was calculated by combining the annual average runoff of each month,and the best improved method under the three standards was obtained,which was compared and analyzed with the original annual distribution method,and the results were verified by Tennant method,monthly minimum runoff method and 90% guarantee rate method.The results show that the ecological flow calculated under the three standards is basically consistent with the annual change trend of the ecological flow calculated by the original year distribution method.The overall trend is:improved method 1(divided by season)>improved method 3(divided by runoff)>original year distribution method>improved method 2(divided by wet and dry months).Compared with Tennant method and other hydrology methods(monthly minimum runoff method and 90% guaranteed rate method),the ecological flow calculated by improved method 1 is better than the original annual distribution method.It can not only meet the needs of fish reproduction and survival and river biological growth,but also guarantee the basic ecological function of the river.Therefore,it is reasonable and feasible to improve the intra-year distribution method.In conclusion,using the improved method-the improved annual distribution method to calculate the ecological discharge can better reflect the change characteristics of the river,conform to the calculation of the seasonal river ecological discharge in the north,and be more suitable for the calculation of the northwest river ecological discharge,which can be used as a new idea for the study of river ecological flow.