黄河中游水沙变化归因分析

Attribution analysis of runoff-sediment variation in the middle Yellow River

采用基于模糊互判断矩阵的层次分析法(fuzzy analytic hierarchy process,FAHP)分析人类活动和气候变化对黄河中游水沙变化的贡献率,并将FAHP法分析的结果与累积量斜率变化率比较法(slope changing ratio of cumulative quantity,SCRCQ)分析的结果进行对比,2种方法计算结果变化规律一致。结果表明:气候变化对径流和泥沙的影响小于人类活动的影响,1970年代、1980年代、1990年代、2000年代人类活动对径流减少的贡献率分别为68%、64%、64%、75%,人类活动对泥沙减少的贡献率分别为45%、65%、59%、69%。

Yellow River is the mother river of Chinese nation and is famous for the most sandiness river in the world.The amount and process of water and sediment have changed significantly at present.And the main problem is that the relationship between the runoff and sediment is uncertain.Human activities and climate change are the most important influence factors.Multiple methods had been applied to study the contribution rates of the two factors to runoff-sediment variation in the Yellow River,such as method of the slope changing ratio of cumulative quantity(SCRCQ),separation evaluation method and double-mass curves of precipitation vs runoff(or sediment load),multiple regression analysis,different series of comparative analysis,hydrological method,soil conservation method and separation judgment method,etc.Many scholars had analyzed the driving factors of runoff and sediment change in the Yellow River basin in the past 40 years based on the method above.And the results varied considerably due to the different assumptions of the methods,data sources and the limitations of the test areas.Fuzzy analytic hierarchy process(FAHP)has an advantage in integrating the research advantages of different scholars to a certain extent.The method based on fuzzy mutual judgment matrix belongs to subjective weight distribution method.The main scoring basis of the evaluation system is the representativeness of the investigative areas.Regional representativeness is measured by the representative coefficients.The representative coefficients are determined by the product of sediment transport ratio and area ratio in the middle Yellow River.And the scoring according to the criteria that if one study area is much more important than the other,then the scoring is closer to 1,and closer to 0 otherwise.There is a hypothetical premise that runoff and sediment discharge are only affected by precipitation.So SCRCQ had been adopted to analyze the attribution of runoff-sediment variation in the middle Yellow River to compare the results of FAHP.The contribution rate of climate change calculated by SCRCQ is equal to the ratio of the slope change rate of cumulative runoff(or sediment transport)to the slope change rate of cumulative precipitation.The results of the two methods were compared.It is showed that the contribution of human activities to runoff and sediment change was greater than that of climate change in different ages.The contribution rate of human activities to the runoff and sediment change in the middle reaches of the Yellow River in different years was consistent:the contribution of human activities to the runoff change first decreased and then increased,and that to sediment change first increased,then decreased and then increased.Climate change contributes the opposite.The impact of human activities and climate change on runoff-sediment variation are also discussed.They proved true based on the analysis of the variation of runoff,sediment and precipitation,as well as water reduction by human activities and sediment reduction by water conservancy and conservation measures.In the 1970s,1980s,1990s and2000s,the contribution rates of human activities to runoff reduction were 68%,64%,64%and 75%,and that to sediment reduction were 45%,65%,59%and 69%,respectively.