利用1960~2009年三江源区枯季月径流数据,分析了退水过程中月径流和退水系数的变化趋势,并利用逐月退水系数重建了枯季径流过程。结果表明:(1)黄河源区和澜沧江源区枯季月径流呈减少的趋势,长江源区呈微弱的增加趋势,枯季径流受控于夏季径流,二者保持一致的变化趋势;(2)黄河和长江源区逐月退水系数的变化趋势在整个退水期是增加的,意味着地下水退水过程减缓,这可能是长期的气候变暖导致江河源区地下水库容增加的结果,在澜沧江源区退水系数的变化没有明显的趋势;(3)可以利用多年平均退水系数和10月径流来重建冬季(11月到来年2月)月径流量,计算值与实测值误差控制在8%以内,拟合精度较高。该研究对认识气候变化背景下三江源区枯季径流特征和水文预报方面具有一定参考价值。

Based on the low-flow data in 1960~2009 in the Three-River Headwaters Region (TRHR), the trends of monthly runoff and the recession coefficient in the runoff recession process were analyzed, and the low-flow process was reconstructed by the monthly runoff recession coefficient. The results showed that: (1) the monthly runoff showed a decreasing trend in the low-flow period both in the Yellow Rivers Headwaters Region (YERHR) and the Lantsang Rivers Headwaters Region (LARHR), and the trend showed a weak increase in the Yangtze Rivers Headwaters Region (YARHR). The low-flow was controlled by summer-flow, and both of them kept a consistent changing trend. (2) The runoff recession coefficient in runoff recession process showed an increasing trend both in the YERHR and YARHR, which means that the runoff recession process was slowed. This is due to increasing groundwater capacity under long-term climate warming. The trend of runoff recession coefficient was not obvious in the LARHR. (3) the winter (from November to February) runoff recession process can be reconstructed by mean monthly runoff recession coefficient and the runoff of October in the TRHR with high simulation accuracy, the difference between the calculated and observed value were less than 8%. The study can provide beneficial reference for understanding the characteristics of low-flow under the background of climate change and hydrologic forecasting in the Three-River Headwaters Region.