Estimation of Effect of Global Warming on Snowmelt Runoff in River of Snowy District

对全球变暖对雪域河流融雪径流的影响进行了预测研究。我们选取了宫城县大仓水坝流域和富山县东里水坝流域作为研究对象，讨论了两个水坝的总径流、融雪径流、融雪季节和积雪消失日期等因素的影响，并建立了两种情景：情景一考虑了降水量随气温升高而增加，情景二则没有考虑。研究结果总结如下：(1)气温升高降低了降水量占降雪量的比例和降雪量。此外，融雪季节和积雪消失日期来得较早。(2)随着4、5月份气温的升高，总径流和融雪径流深度显著减小，而3、2月份融雪径流深度略有增加。(3)情景II的总径流和融雪径流深度的下降幅度大于情景1。(4)大仓大坝流域和环状流域在总径流和融雪径流的下降百分比上没有显著差异。另一方面，托里坝流域的总径流和融雪径流深度明显减少，降幅是其他流域的2~3倍。(5)可以预见，全球变暖对雪区河流融雪径流的影响较大。

Our research deals with the forecast of the effect of global warming on snowmelt runoff in rivers of snowy district. The basins we select for our research are the Okura dam basin in Miyagi prefecture and Tori dam basin in Toyama prefecture.We have discussed the effect from total runoff, snowmelt runoff, snowmelt season, and snow cover disappearance date that these two dams show, and have also established two scenario : Scenario I takes into consideration an increase in precipitation with the rise of temperature and Scenario II does not.The summary of the results is shown below.(1) The rise of temperature reduced the percentage of precipitation to snowfall and the water equivalent of snow. Moreover, the snowmelt season and the snow cover disappearance date came earlier. Therefore, we can see remarkably early snowmelt runoff and its decrease in volume.(2) The depth of total runoff and snowmelt runoff decreased abundantly, with the rise of temperature in April and May, and, on the contrary, the depth increased a little in March and February.(3) The depth of total runoff and snowmelt runoff showed a greater decrease in Scenario II than in Scenario I.(4) There was not a significant difference between the Okura dam basin and the Tori in the percentage of decrease in total runoff and snowmelt runoff. On the other hand, the Tori dam basin showed a marked decrease in the depth of total runoff and snowmelt runoff : it had two to three times greater decrease than the other one.(5) Thus, it can be predicted that global warming has a large effect on snowmelt runoff in river of the snowy district.