Study on Inhomogeneity of Snowmelt Water Percolation in Snowpack

通过对积雪头盆融雪径流响应的研究，发现积雪中融雪水入渗与土壤中融雪水入渗同等重要。然而，积雪融化水在积雪中的渗透还没有得到很好的了解，特别是对积雪的浓缩机理还没有很好的了解，积雪头盆融雪径流峰值到融雪的时间滞后的年际差异是由于积雪的层结不同，特别是冰层在积雪中的数量和位置的不同造成的。在积雪底部设置多室蒸渗仪(MCL)，测量积雪底部融雪水流量的不均匀性。利用MCL模拟结果建立了融雪水入渗模型，并将该模型与整个流域径流模型相结合，模拟了流域末端融雪水的径流过程。成功地对径流进行了重建，解释了峰值径流与峰值融雪时滞的差异，融雪速率日进程的形状近似于高斯分布曲线。并假定积雪中的融水通量速度与融水通量的a次方成正比，将入渗波表示为时间的函数。该模型重建了积雪内部的融雪流量，利用TDR测量了积雪中融水含量的变化，TDR测量了积雪的介电常数，介电常数与液态水含量高度相关。冰层以上的介电常数大于冰层下的介电常数，冰层上方的介电常数并不总是和所有地方的大。本研究明确了水平分层积雪中融雪水的部分渗透，但坡面积雪中的渗透机理尚未得到解答。

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.