The Runoff on the Snowfall Source Basins

降雪和融雪现象似乎是非常好的雨水储存功能。融雪期间的流量占全年流量的40%~60%。由于4月至6月是融雪期，农业水利工程在大坝管理方面存在着非常重要的问题。由于索拉奇河上游卡纳亚姆大坝的修建，径流特征发生了变化，枯水流量增加，洪水流量减少。Ishikari河源流域的径流存在地区差异。在竹内山脚下，一年的流量很小。另一方面，在雪冈贝苏山脚下和青山大坝的上游盆地，流量很大，约3000毫米。在枯水径流方面，由于降雪期降雨以雪的形式储存，降雪期的最小流量小于降雨径流流量。认为无降雨情况持续较长时间是同一现象，这是ABLO的看法。一年至少5天的平均流量与出现该值前n天的降雨量有一定的相关性。在Horobetsu盆地中，n=25具有最高的关联值。另一方面，在奥尤巴里盆地，相关系数最大为0.71，n=70.5。在寒冷地区的坝池中，有必要考虑降雨系数。这是位置(平面、点)和高度的系数。该系数的值很大，相当于流域降雨量的1.5~2.0倍。

The phenomena of snowfall and snow melt are seemed very excellent storage functions of rain. The discharge during snow melting period occupies from 40 to 60 percent of a year discharge. Because the snowmelting period from April to June, there are very important problems at agricultural hydrotechnics as regards dam management.1. Because the construction of the Kanayam Dam at the upper basins of the Sorachi river, there is a change of runoff characteristics which are increase of low-flow and decrease of flood flow.2. The runoff of the source basins at the Ishikari river is regional differences. At the foot of the Tokachi Mountain, the discharge for a year is very small. On the other hand, at the foot of Syokanbetsu Mountain and the upper basins of the Aoyama dam, it is a great deal of discharge, about 3000mm.3. About low flow in dam basins, because rain fall stored as snow for snowfall period, the least discharge for snowfall period are smaller than for rainfall-runoff. It is ablo to regard it as the same phenomenon that non-rainfall circumstances continue for a long time.4. There is a correlation between the average discharge of the least five days for a year and the rain fall for n days before this value is occurred. At the basins of Horobetsu basins, there is the highest correlation value in n = 25. On the other hand, at Oyubari basins, the correlation coefficient is 0.71 as biggest value, in n = 70.5. At the basins of dam in cold regions, it is necessary to consider the coefficient of rain fall. This is the coefficient for place (plane, point) and for height. The value of the coefficient are very large and equal to the rainfall from 1.5 to 2.0 times as much as observed rainfall for basins.