Proceses to runoff from snowfall in the catchment area of Lake Biwa

水文观测是在志贺县阿多河的支流柳谷流域进行的。古生代下的柳谷流域被落叶阔叶林覆盖。流域面积70ha，内部子流域面积4.06ha。首先，利用1978 ~ 1983年每年4 ~ 11月无雪季节的逐时和逐日降水和流量资料，在降水综合径流模型HYCYMODEL上确定径流常数。结果表明，由于两个流域的运动常数相同，因此水文通道的转换可以忽略不计，并且柳谷流域的直接径流量占总径流量的比例低于花岗岩下垫的吉柳流域。其次，模拟了降水和气温作用下的积雪和融雪过程。结果表明，积雪深度和流量在大部分年份与实测资料吻合较好，在降雪量较大的年份与实测资料吻合较差。为了获得进一步的一致性，需要对融雪模型进行改进。

The hydrological observation has been carried out in the Yanagatani catchment where is a tributary of Ado River, Shiga Prefecture. The Yanagatani catchment underlain by Palaeozoic is covered by deciduous bload-leaved forest. The basin area is 70ha, and the interior sub-basin area is 4.06ha. Firstly, the hourly and daily data of rainfall and discharge in a non-snow season from April to November, every year during 1978 to 1983, were used for determination of the runoff constants on HYCYMODEL which is a synthetic runoff model for rainfall. The results show that the transformation of hydrographin channels is negligible because the constants of motion are the same values in both basins, and that the ratio of direct runoff for total runoff in the Yanagatani catchment is lower than in the Kiryu catchment underlain by granite. Next, the processes of snowpack and snowmelt from precipitation and air temperature are modelized. As a result, the predicted snow depth and streamflow agree well with the observed data in the most of years, and don't agree so well with the observed in the year with heavy snowfalls. It needs a improvement on the snowmelt model to obtain further agreement.