Study on Generalization of the Snowmelt Runoff Estimating Methods

在规划灌溉和其他水资源利用时，掌握融雪过程，了解融雪对河流径流的影响是非常重要的。为此，建立了实验流域，并对与融雪有关的因素进行了观测。通过雪-土界面的热传递引起的融雪称为底部融雪。反映底部融雪对融雪径流机制研究的影响是非常重要的。但是，很少有估算积雪期底部融雪量的例子。为了改善这一状况，选取北海道至东海地区的11个点作为研究对象，估算了底部融雪量并进行了比较。另一方面，在融雪季节，大多数融雪现象发生在积雪表面。融水渗透到地表是有时间差的。为了预测融雪径流，有必要了解融水在积雪中的渗透机制。因此，测量了用于估算地表融水和地表融水的气象因子。对提出的冰川区渗流模型进行了改进，利用该模型从地表融水量估算地表到达量。结果表明，应用该方法，在图的峰值时间之后的时间内具有较好的再现性，而在激波锋的形成过程中有一定的损失。作为研究计划的一部分，在几个流域估计了雪的水当量，并测试了全球变暖对春季河流流量的影响。

When planning irrigation and other water utilization, it is very important to grasp the process of snowmelt, and to understand how the snowmelt affects river runoff. For this purpose the experimental watershed was set up and factors concerned the snow melt were observed.Snowmelt which is caused by heat transfer across the snow-soil interface is called bottom snowmelt. It is very important to reflect the influence of bottom snowmelt on research regarding the mechanism of snowmelt runoff. But there have been very few examples of estimating the amount of bottom snowmelt during snow-covered period. In order to improve this situation 11 points where ranging from Hokkaido to Tohkai Regions were selected as research subjects and amount of bottom snowmelt was estimated and a comparison was conducted.In the other hand in the melt season, most snowmelt phenomenon occurs at the surface of the snowpack. Meltwater percolates to the ground surface with time lag. To forecast snowmelt runoff, it is necessary to understand the mechanism of meltwater percolation in snow cover. Thus, meteorological factors used in estimating surface melt and meltwater at the ground surface were measured. The percolation model, proposed for glacial area, was improved, then using this method, ground arrival amount was estimated from surface melt amount. As a result, it was determined that by applying the method, preferable reproducibiilty could be achieved for the time after the peak time of the graph, while there was amount loss regarding formation of shock front.As a part of the study program, water equivalent of snow was estimated at several watersheds and effects of global warming on spring river flow was tested.