Abstract
Snow water equivalent (SWE) increases linearly against the elevation in mountains below the forest limit, but this effect is not quantitatively evaluated when it is extrapolated above the forest limit. In this study, snow surveys were carried out not only below the forest limit but also above there. The study area was Mt. Makihata in Niigata prefecture during the springs in 2002 and 2003. SWE increased linearly against the elevation below the forest limit, but it decreased rapidly above there. The distributions of SWE in the basin were calculated and compared, based on the two kinds of altitudinal distribution of SWE above the forest limit; one was the traditional method that SWE was extrapolated from the distribution below the forest limit, and the other was based on the snow surveys above there. The basin of Uono river above Muikamachi was extracted from the digital elevation model, and the areal distribution of snow-cover in the basin was calculated from remote sensing analyses. The differences of SWE in the basin could be neglected in lumped models, because the differences were 8-12 % on average in the basin, being almost same as the observational errors of the precipitation or the river discharge. In distributed models, the differences of SWE were up to 300 % in the ridges of the mountains. In addition, the imbalance of wind-induced snow movement among basins was indicated, because the area above the forest limit in the basin has more slopes of windward than those of leeward.
