拉萨河流域近50 年来径流变化趋势分析

以拉萨水文站以上流域为研究区, 基于拉萨水文站和唐加水文站的水文实测数据和当雄 县等3 个气象站的气候观测数据, 统计分析了1956~2003 年研究区径流的年内、年际变化, 利用 Mann- Kendall 趋势分析法和Pettitt 变点检验法分析了拉萨河流域径流的变化特征, 采用多元回 归方法分析了气候因素( 气温、降水) 对径流变化的影响。结果表明: ( 1) 研究时段内, 径流年际变 化波动较大, 在1970 年前后径流发生了较大的突变, 呈现出明显的增加趋势, 尤以近20 年来的 趋势最大; 月均径流的年际变化中, 有增加趋势的主要分布在冬半年( 11～4 月) 和夏半年的个别 月份( 5、7、9 月) ; ( 2) 流域内气候变化趋势与径流变化趋势基本一致, 但不同月/年均径流受不同 气候因素影响, 主要表现在年平均尺度上受降水影响较大, 在月平均尺度上, 夏半年径流增加趋 势受降水增加影响较大, 而冬半年径流变化则主要与气温有较显著相关性, 其主要原因可能是全 球变暖导致冰川融水增加。

Trend Analysis of the Runoff Var iation in Lhasa River Basin in Tibetan Plateau during the Last 50 Years

Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan plateau as a study objective, the characteristics of the annual and monthly mean runoff in 1956-2003 were analyzed, which were based on the hydro-data of the two hydrological stations (Lhasa and Tangga) and the meteorological data of the three meteorological stations (Damxung, Lhasa and Tangga). The trends and the change-points of runoff and climate from 1956 to 2003 were detected by using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between the runoff and climate change were analyzed by using multiple linear regression. The major results could be summarized as follows: (1) The annual mean runoff in 1956~2003 is characterized by a great fluctuation and a positive trend with two change-points (around 1970 and the early 1980s), after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides the annual mean runoff, the monthly mean runoff with a positive trend is in winter half year (from November to April) and summer half year (May, July and September). (2) The trends of the climate change in the study-area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter.