黄河流域近40年蒸发皿蒸发量变化趋势分析

Analysis on the Long-Term Trend of Pan Evaporation in the Yellow River Basin over the Past 40 Years

本文对黄河流域内58个站点1960-2001年逐月20cm口径的蒸发皿蒸发量数据进行统计检 验,并时检验结果进行了趋势分析。结果表明:近40年黄河流域蒸发皿蒸发量大部分地区呈现出明显 的下降趋势,时间上以典型月4月和7月下降幅度最为明显,地域上以三花干流区间和伊洛河流域地 区下降幅度为最大;本文采用的两种检验方法得到的结论具有较好的一致性。另外,本文对黄河流域 1970-2001年蒸发量分布规律也进行了简要分析,得出整个黄河流域的年平均蒸发量分布规律是从东 北部向西南部地区逐渐减少。

Evaporation is a key element in the hydrologic cycles. It is a very important process in water resources assessment, drought monitoring, hydraulic structure design, hydrologic research and crop production prediction. Since the 1980s, the shortage of water resources in the Yellow River Basin has become more and more serious with the development of local economy and society. The total amount and the spatial distribution of water resources in the Yellow River must be estimated accurately, in which evaporation is an important component, to be estimated. One of the commonly used tools for detecting long-term changes of hydrologic time series is trend analysis method. A number of statistical test methods have been proposed to assess the significance of trends in a time series. In this paper, the Mann - Kendall statistic method and linear trend estimation are used to analyze the long-term trend of evaporation at 58 hydrologic stations in the Yellow River Basin from 1960 to 2001. The results show that the trend of pan evaporation in the Yellow River Basin over the past 40 years almost steadily decreased and the degree of declining is greater than that of rising, especially in April and July. The results of two methods coincide well with each other. In addition, the temporal and spatial distribution of pan evaporation is analyzed briefly in the Yellow River Basin from 1970 to 2001. The results show that the average evaporation in the study area in January over the whole Yellow River Basin decreases gradually from southwestern and northwestern part to middle part and northern part. The spatial distribution of the evaporation in July is similar with mean annual evaporation, both decrease gradually from northeastern part to southwestern part.