Abstract
Snowmelt plays an important role regarding water resources problems in Hokkaido where snowmelt runoff accounts for about 50% of the annual runoff in most of the rivers. The degree-day method is the simplest approach to analyze the snowmelt mechanism in mountainous catchments, especially when there are little meteorological and hydrological data. In a previous report, the authors determined that there was a constant flux ratio between interflow and underground water flow that has a day-delay of flux. The present paper addresses the analysis of snowmelt runoff using the degree-day method and these previous results. Information on the change in the snow covered area derived from LANDSAT data is also employed to estimate the catchment-wide snowmelt.
The main results obtained herein are as follows:
i) In the study catchment, the simple model applied with the snowmelt amount resulting from use of degree-day factor and coupled with the previous runoff characteristics was in good agreement with the obierved discharge volume. Snowmelt runoff was systematically explained using this simple model.
ii) The catchment-wide snowmelt was obtained by superposing snowmelt amounts in the subcatchments divided according to elevations in which the mean daily temperature in each divided zone was corrected by using the lapse rate. The result is good from a practical standpoint, so the catchment snowmelt is essentially explained by the degree-day factor.
iii) The model was able to estimate the snowmelt amount from the change in the snow covered area that was derived through LANDSAT data. It was proven that the estimated discharge amount coincided with the observed discharge amount.
