基于Budyko假设和分形理论的水沙变化归因识别——以北洛河流域为例

全球气候变化及人类活动深刻影响了区域水文过程,进行水沙变化归因识别对流域生态保护和高质量发展尤为重要。基于Budyko假设和分形理论,采用弹性系数法,对北洛河流域上（丘陵沟壑区）、中（土石山林—高塬沟壑区）、下游（渭北旱塬农区）3种不同地貌和植被类型区1959—2019年的水、沙通量变化进行归因分析。结果表明,北洛河上、中、下游径流量均显著减少,由20世纪60年代的35 mm、32 mm、34 mm,减少到21世纪10年代的19 mm、24 mm、6 mm,60 a减少率分别为0.3 mm a^-1、0.2 mm a^-1、0.4 mm a^-1。上游输沙量极显著减少,中游降低趋势不显著,下游显著减少,由20世纪60年代的99×10⁶ t、8×10⁶ t、3×10⁶ t,减少到21世纪10年代的10×10⁶ t、3×10⁶ t、0.3×10⁶ t,60 a减少率分别为1.5×10⁶ t a^-1、0.04×10⁶ t a^-1、0.1×10⁶ t a^-1。20世纪70年代以来,上游径流变化逐渐受人类活动影响,且影响程度逐渐增强,21世纪10年代人类活动贡献率达66.3%;气候变化是中游径流变化的主控因子,21世纪10年代降雨和潜在蒸散发的贡献率分别为77.0%和20.2%;下游径流减少主要为人类活动影响,21世纪10年代其贡献率为64.3%。对比20世纪60年代流域输沙量变化始终受人类活动主导,21世纪10年代人类活动对上、中、下游输沙量减少的贡献率分别为80.7%、59.2%和92.7%。上游人类活动对输沙量减少的贡献中,退耕还林等沟坡措施和沟道工程措施分别为39.0%、42.7%,中、下游人类活动贡献的估算结果反映出高植被覆盖区和农区汲水灌溉对区域水、沙的影响特征。

Attribution recognition of streamflow and sediment changes based on the Budyko hypothesis and fractal theory:A case study in the Beiluo River Basin

Global climate change and human activities have profoundly affected regional hydrological processes. Attribution recognition of streamflow and sediment change is particularly important to understand the theory and practice of ecological protection and for high-quality development of watersheds. Based on the Budyko hypothesis and fractal theory, we used the elastic coefficient method to analyze the attribution of streamflow and sediment changes in the upper (typical hilly and valley region), middle (earth-rock mountain forest region and tableland region), and lower (Weibei loess tableland agricultural region) portions of the Beiluo River Basin from the 1960s to the 2010s. Results showed that runoff depth in the upper, middle, and lower reaches of Beiluo River decreased significantly from 35, 32, and 34 mm in the 1960s to 19, 24, and 6 mm in the 2010s, with a decrease rate of 0.3, 0.2, and 0.4 mm/a, respectively. The upstream sediment transport decreased significantly, while the sediment transport of the middle reaches decreased insignificantly; the downstream sediment transport also decreased significantly from 99, 8, and 3 million tons in the 1960s to 10, 3, and 0.3 million tons in the 2010s, with decreasing rates of 1.5, 0.04, and 0.1 million t/a, respectively in the 60 years. In contrast to the 1960s, the runoff change in the upstream region has been gradually affected by human activities since the 1970s, and its degree has gradually increased as the contribution rate of human activities in the 2010s reached 66.3%. Runoff variation in the middle reaches was mainly determined by climate change, with the contribution rates of rainfall and potential evapotranspiration being 77.0% and 20.2%, respectively. The decrease of runoff in the downstream region was mainly affected by human activities, and the contribution rate was as high as 64.3% in the 2010s. In contrast to the 1960s, the change of sediment yield in the basin was always dominated by human activities, and the contribution rates of human activities to the reduction of sediment discharge in the upper, middle, and lower reaches in the 2010s were 80.7%, 59.2%, and 92.7%, respectively. Measures such as returning farmland to forests on slope and engineering practices in valley contributed 39.0% and 42.7%, respectively, of the reduction in sediment transport in the upstream region. The estimation results of the contribution of human activities in the middle and lower reaches reflect the response of regional runoff and sediment transport in high vegetation cover areas and in irrigated agricultural areas.