Analysis of Evapotranspiration Process for Working System Planning in Water Resources Conservation

本研究采用三种方法从根本上对蒸散量进行分析。第一部分是利用涡旋相关法对实际资料进行分析，直接测量蒸散量；第二部分是将短期水量平衡法应用于日降雨量和日径流量的研究；第三部分是日流量历时曲线分析的研究。1.对位于碧瓦湖东侧的爱知大学森林和基诺本镇两个起伏地形上的林冠进行了湍流输运的测量。用涡旋相关法测得的动量t_u和感热H的湍流通量来检验体积法的拟合优度。结果表明，就u^*与U的相关性而言，林地样地数据分布广泛，且与稳定性密切相关，而平地数据满足线性相关。2.利用爱知大学森林两个小流域56年的径流资料，试图识别一长系列流量历时曲线的趋势，以描述物理过程的渐变对森林生长的影响。通过简单回归模型的对比分析，发现两流域流量历时曲线上的第6~220天流量在几十年的过程中呈线性增长。3.对日流量和降水量数据应用短期水量平衡法计算蒸散量。用简单模型对流域湿度引起的差异进行修正后，发现三个流域的林分蓄积量与蒸散量指示值之间存在较好的相关性。

In this study three methods were adopted to analyze evapotranspiration fundamentally. The first one is a study analyzing actual data with eddy correlation method to measure directly evapotranspiration, the second is a study to apply short term water balance method to daily precipitation and daily runoff, and the last is a study to analyze discharge duration curve on daily discharge rate.1.Measurement was conducted to turbulent transport on forest crown which locate on rolling terrain in two study sites, University Forest in Aichi and Kinomoto Town in east side of Biwa Lake. Turbulent flux of momentum tau and sensible heat H which was measured by eddy correlation method were used to check goodness of fit on bulk method. The result shows that as to the correlation between u^* from tau and U,the data plots of the forest site were scattered widely, and were closely related to stability, however, the flat field data satisfied the linear correlation.2.Attempt has been made to identify trends in a long series of discharge duration curve for describing the effect of gradual change in physical processes with forest growth using 56-year discharge records in two small experimental watersheds in the University Forest in Aichi. It was found that the 6th to 220th day discharge on the discharge duration curve linearly increased over the course of several decades in both watersheds using comparative analysis with simple regression models.3.Short term water balance method was applied to the data of daily discharge and precipitation to get evapotranspiration. After correcting the difference caused by watershed wetness with simple model, good relationship between stand stock of forest and indication value on evapotranspiration was found in three watersheds.