雅砻江流域中上游径流变化归因分析

在全球气候不断变化和人类活动的影响下,开展河川径流变化的归因研究对水资源的合理利用和分配具有现实意义。以雅砻江流域雅江水文站以上区域作为研究区,采用线性分析、Mann-Kendall检验法和累积距平法等方法分析了研究区1961～2015年水文气候要素的变化特征,进而基于Budyko假设水热耦合平衡原理的弹性系数法估算了径流变化对各影响因子的弹性系数,并对研究区的径流变化进行归因分析。结果表明:近55年来,研究区年径流深整体呈上升趋势,上升速率为0.496 mm/a,并在1999年发生了由低到高的显著突变。年降水量和潜在蒸散量分别呈上升和下降趋势,变化率分别为0.994和-0.246 mm/a。降水、潜在蒸散发和下垫面弹性系数分别为1.40、-0.40和-0.83,说明年径流对降水量的变化最为敏感,其次是下垫面变化,对潜在蒸散量变化的敏感度最低。年径流对气候变化的敏感度呈微增强趋势,对下垫面变化的敏感度逐步减弱。气候变化是年径流增加的主要因素,总贡献率为60.66%,其中降水量和潜在蒸散量的贡献率分别占59.21%和1.45%,下垫面变化的贡献率为39.34%,反映下垫面变化的NDVI自1999年后呈下降趋势,是导致径流增加的重要原因。

Attribution Analysis of Runoff Variation in the Upper-Middle Reaches of Yalong River

Under the influence of global climate change and human activities, attributing river runoff changes is practically significant for the rational use and distribution of water resources. In this study, we selected the upstream areas of Yajiang Hydrological Station in the Yalong River Basin as the research area. The linear regression, Mann-Kendall test and cumulative anomaly method were used to analyze the characteristics of hydrological and climatic elements in the study area from 1961 to 2015. Based on the coupled water-energy balance principle of Budyko hypothesis, we estimated the elastic coefficient of the runoff variation corresponding to each influencing factor using the elastic coefficient method, and conducted the attribution analysis on the runoff variation. The results show that in the past 55 years, the annual runoff depth of the study area in general increased at 0.496 mm/a, and a significant change from low to high occurred in 1999. The changes of annual precipitation and potential evapotranspiration show an increasing trend at 0.994 mm/a and a decreasing trend at -0.246 mm/a, respectively. The elastic coefficients of precipitation, potential evapotranspiration and underlying surface are 1.40, -0.40 and -0.83, respectively, indicating that the annual runoff was most sensitive to the change of precipitation, followed by the change of the underlying surface; the sensitivity to the change of potential evapotranspiration was the lowest. The sensitivity of annual runoff to climate change was slightly enhanced, while its sensitivity to the change of underlying surface was gradually weakened. Climate change was the dominant factor contributing to the increase of annual runoff, and its contribution is 60.66%, in which the contribution of precipitation is 59.21%, the contribution of potential evapotranspiration is 1.45%, and the contribution of underlying surface changes is 39.34%. NDVI, which represents the underlying surface, showed a decreasing trend since 1999, and is an important reason for the increase of runoff.