Study on Inhomogeneity of Snowmelt Water Percolation in Snowpack

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Runoff response of snowmelt in a snowy head basin was investigated and found that snowmelt water infiltration in snowpack is as important as that in soil. However, the infiltration of snowmelt water in snowpack has not been understood well, especially on concentration mechanism.The yearly difference in time lag of peak snowmelt runoff of the snowy head basin to snowmelt was found to be caused by the difference in stratification of snowpack, especially the number and the position of ice layr in the snowpack. A multi-compartment lysimeter (MCL) was set to the bottom of snowpack to measure an inhomogeneity of the snowmelt water discharge at the bottom of snowpack. A snowmelt water infiltration model was developed using the result of the MCL.Then, this model was combined to a whole watershed runoff model to simulate the snowmelt water runoff at the terminus of the watershed. It successfully reconstructed the runoff and explained the difference in time lag of peak runoff to the peak snowmelt.The shape of daily course of snowmelt rate is resemble to the Gaussian distribution curve. Combined with that the meltwater flux speed in snowpack is assumed to be proportional to the a power of meltwater flux, the infiltration wave was expressed with a function of a time. This model was reconstructed the snowmelt flux inside the snowpack.Change in meltwater content profile in snowpack was measured using a TDR.The TDR measure the dielectric constant, which is highly correlated with the liquid water content. The dielectric constant above the ice layr is larger than that beneath the ice layr, and it is not always and everywhere larger above the ice layr.This study has made clear a part of snowmelt water infiltration in horizontally stratified snowpack., however, the infiltration mechanism in snowpack on a slope left unanswered.