基于Budyko假设的三江源径流变化特性及量化分离

Variation Characteristics of Runoff and the Quantitative Separation Based on Budyko Hypothesis in the Three-River Headwaters Region

摘要:

根据1956—2012年气象和水文站点的降雨、气温、蒸发等实测和相关数据，采用线性趋势法、非参数Mann-Kendall法和Spearman法，分析了三江源地区降雨、气温、NDVI（归一化植被指数，normal difference vegetation index）和径流变化特征，并采用基于Budyko假设的互补关系权重因子法量化分离气候和下垫面对径流影响。结果表明，长江源和澜沧江源降雨量呈显著增加趋势，三江源气温呈显著增加趋势，黄河源NDVI呈显著增加趋势。长江源、黄河源和澜沧江源径流量10年变化幅度分别为6.54亿m3、-2.05亿m3和1.54亿m3。所使用的互补关系权重因子法不仅可以准确地计算出径流年均值的变化，并且量化分离时无需假定气候和下垫面变化对径流变化具有相同的贡献特征。总体来说，长江源、黄河源气候和下垫面变化对径流的影响为正贡献；但是澜沧江源（权重因子）等于1.0时下垫面变化对径流的影响为正贡献，而为0.5 和0时下垫面对径流的影响为负贡献。长江源、黄河源和澜沧江源气候变化对径流的贡献分别为55.21%~92.85%、52.47%~68.50%、89.91%~124.58%。三江源径流变化主要受到气候变化影响，降雨量是气候变化影响径流的主要控制因子，植被覆盖是下垫面变化影响径流的主要控制因子。

关键词:三江源;径流;气候;下垫面;归一化差分植被指数

Abstract:

Based on the measured and related data from meteorological and hydrological stations in the Three-River Headwaters Region during 1956—2012, the variation characteristics of precipitation, temperature, NDVI (normal difference vegetation index) and runoff were analyzed by using the linear regression method, Mann-Kendall test method and Spearman test method. Moreover, the influences of climate and the underlying surface to runoff were analyzed by using the weighting factor method based on Budyko hypothesis. The results indicated that the annual precipitation showed a significant increase trend in the source region of the Yangtze River and Lancang River, and the annual mean temperature showed a significant warming trend in the Three-River Headwaters Region. The annual NDVI showed a significant increase trend in the source region of the Yellow River. In addition, the changing slopes of annual runoff in the source region of the Yangtze River, Yellow River and Lancang River were 6.54×108m3,—2.05×108m3 and 1.54 ×108m3 per 10 years, respectively, but these trends were not significant. The weighting factor method used in this study can not only accurately estimate the annual mean runoff, but also need not to assume that the climate and underlying surface changes have the same contributions to runoff changes. Overall, both climate and underlying surface showed a positive contribution to runoff changes in the source region of Yangtze River and Yellow River. However, in the source region of Lancang River, the underlying surface is positive contributing factor to runoff variations when the weighting factor (i.e., ) was 1.0, whereas it was a negative contributing factor when was 0.5 and 0. The contributions of climate change on runoff in the source region of the Yangtze River, Yellow River and Lancang River were 55.21%~92.85%, 52.47%~68.50%, and 89.91%~124.58%, respectively. Meanwhile, our results emphasized that the changes of runoff in the Three-River Headwaters Region were mainly affected by climate change. Precipitation is the main controlling factor of climate that influences runoff, and vegetation cover is the main controlling factor of underlying surface that influences runoff.

Key words:the Three-River headwaters region;runoff;climate;underlying surface;normalized difference vegetation index