Bulletin of Glaciological Research ,0 (,**2) +ῌ2
ῌJapanese Society of Snow and Ice

1Water balance and mass balance in a mountainous river basin, Northern Japan AlpsKeisuke SUZUKI+, ,, Takayuki KURAMOTO+, Motoki TANAKA, and Shailendra Kumar SHAH+ Department of Environmental Sciences, Faculty of Science, Shinshu University Matsumoto, -3*ῌ20,+ Japan, Institute of Mountain Science, Shinshu University, Matsumoto, -3*ῌ20,+ Japan- Interdisciplinary Graduate School of Science and Technology, Shinshu University Matsumoto, -3*ῌ20,+ Japan(Received April ., ,**2; Revised manuscript accepted May 1, ,**2)

Abstract
We have investigated the water balance and mass balance for four years in Maekawa River basinon the eastern slope of Mt. Norikura-dake. In this region, the precipitation frequency is high from therainy season to the autumn. The maximum base-ﬂow discharge occurs in the spring snowmelt
season. The pH and electric conductivity of the river water decline rapidly with the beginning of thesnowmelt runo# and temporarily decrease when the discharge increases temporarily in the rainyseason or during a typhoon event. The Clῌ concentration of the river water increases in the earlystage of snowmelt season since there is a considerable amount of sea salt in the snow. In addition, theNO-ῌ concentration of the river water increases when the rainfall increases the discharge. The major
ion concentration of the river water, except Clῌ and NO-ῌ almost synchronizes with the change in theelectric conductivity. In the mass balance of cations, the runo# rate from the river basin considerably exceeds the atmospheric deposition rate to the river basin. This is because there is extremelymuch elution of ions from new volcanic rocks and soils. Further, the atmospheric deposition rate ofNO-ῌ is larger bigger with the biological consumption in the river basin than the runo# rate from thebasin.

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Introduction

For heavy-snow regions such as Japan Sea-side
area, the quantity of water precipitated by a snowfall
is extremely more important than rainfall as a waterresource. Moreover, snow also plays a role of natural
dams since it accumulates in river basins during winter time. The snowfall in mountainous regions ismore than that in the lowlands; however, it is di$cultto determine quantitatively. The snowfall measurement using a regular precipitation gauge requires aheater and therefore an electrical power supply.
Moreover, the measurement accuracy is low becauseof a low capture rate of snowfalls in windy mountainous regions (Yokoyama et al., ,**-). For these reasons, snowfall is rarely measured using a precipitation
gauge in mountainous regions during the winter season. Precipitation-gauge stations are set up by theJapan Meteorological Agency in mountainous regions
only during warm periods; moreover, the number ofstations is extremely small. It is crucial to elucidate
the water balance by quantitatively comprehending
the amount of precipitation and also including thesnow in mountainous regions from the aspect of wa-ter resources.
Further there are reports that state that the snowfall in Japan decreases in accordance with global warming (Inoue and Yokoyama, ,**-). However, this result is from research based on data mainly from lowlands; therefore, it is uncertain whether this data applies to mountainous areas at high altitudes. In asnowy temperate area, where rain or temporary warming can cause frequent melting at the surface ofsnow cover, the snow melts due to an increase in the
air temperature and the temperature determines whether the precipitation will be in the form of snow orrain. At such places, the snow turns to rain or viceversa depending on increases and decreases in temperature. In addition, it is likely that the snowfall
decreases if the climate becomes warmer since snow
particles melt while falling and turn into rainfall;thus, the precipitation amount is the same. However,
it is also conceivable that the snowfall will increase inmountainous regions at high altitudes. This is because the saturation vapor pressure in the atmosphere
increases with temperature. Therefore, snowfall will
increase if the precipitable water is increased in amount and dose not turn into rain. Inoue and Yokoyama(+332) predicted that the snowfall will not increase for