中亚阿姆河上游产流过程特征研究

Runoff generation in the headwater of Amu Darya, Central Asia

阿姆河是中亚最大的一条河流,其径流主要来源于西天山和帕米尔高原的积雪、冰川融水,由于地处高山区,数据获取困难,对其产流的具体组成与季节分布特征认识不足。本文利用分布式水文模型模拟阿姆河1951-2005年的产流过程,分析雪、冰融水年内分布和年际变化特征以及气候变化的影响。结果表明:1阿姆河产流区融雪集中在3-7月,冰川产流在6-9月,雨、雪、冰产流比例分别为18%、67%和15%,雪、冰融水产流超过80%;2阿姆河总产流集中在4-9月,占年产流量的83%,地表流、基流和侧向流分别占径流量的38%、46%和16%;3 MannKendall非参数检验(α=0.05)显示,1951-2005年间,阿姆河产流区降水呈显著减少趋势,气温呈显著升高趋势,雨、雪、冰产流量与总产流量均呈减小趋势,特别是在1995年之后,由于气温的持续上升和降水急剧下降,产流量减少幅度加大,1996-2005年与1951-1995年相比,雨、雪、冰产流分别减少35%、20%和4%,总产流减少了21%。

Amu Darya is the largest river in Central Asia that provides water resources to downstream water users and flows into the Aral Sea. Runoff of the Amu Darya River is dominated by snowmelt and glacier melt originating from the alpines. Quantification of snowmelt and glacier melt contribution to the runoff is important for understanding the dynamic characteristics of the streamflow. This study investigates the glacier and snow melt processes in the headwaters of Amu Darya by using a glacier-enhanced SWAT model. The simulations were run through 1951 to 2005. The results indicate that the SWAT- RSG model could well estimate the monthly streamflow process of the Amu Darya River Basin, and the efficiency coefficient and absolute value of PBIAS in the calibration period(1961- 1975) and validation period(1976- 1985) could be higher than 0.6 and lower than25%, respectively. Snowmelt and glacier melt contributed 67% and 15% of the annual runoff. The Amu Darya River is mainly supplied by melting high-mountain snow and glaciers, which was concentrated in March to July and June to September, respectively. Owning to the combined effect of rainfall, snowmelt, and glacier melt, the runoff is concentrated in April to September, accounting for 83% to the total runoff, and the peak occurred in July. The results of Mann-Kendall trend analysis indicate that precipitation showed a significant decreasing trend and temperature showed a significant increasing trend from 1951 to 2005, and experienced a sudden jump in1995. Due to the change of temperature and precipitation, snowmelt showed a decreasing trend and the value during 1996 to 2005(Period Ⅱ) was 20% lower compared to that in 1951 to 1995(Period Ⅰ). Due to the shrink of glacier area and reduction of precipitation, glacier melt showed a non- significant decreasing trend between1951 and 2005 and the annual glacier melt in Period Ⅱ was 4% less than that in Period Ⅰ. Despite that the rainfall had slightly increased, the rain runoff was reduced by 35% as a result of the increased evapotranspiration. Consequently, the streamflow was reduced by about 260 million m3 each year from 1951 to2005. The runoff showed a 21% reduction from Period Ⅰ to Period Ⅱ. The study of runoff generation characteristics in the headwaters of the Amu Darya River can provide references for the water resource management in the Amu Darya River Basin and Central Asia.