Numerical simulations of freeze/thaw cycle and its impact on groundwater recharge in sub-Arctic environment

In sub-Arctic environment as in Finland, soil moisture and temperature dynamics affect the development of soil frost that controls snowmelt runoff, infiltration and recharge in winter periods. This study was initiated to investigate the performance of integrated hydrology model Amanzi-ATS, in simulating dynamics of soil moisture and temperature at different depths to assess recharge rate in unconfined aquifer in Central Finland. Our objective is to study intra- and inter-annual recharge rates, and the impacts of soil ice on groundwater recharge rate. Hourly soil water content and temperature was measured at ten different depths. The groundwater depth and temperature were measure daily from the borehole located 2 meters from the soil monitoring station and the climate data was obtained around 5 km from the soil station. 1D model with varying soil texture was developed to predict recharge rates. Measured soil water content, soil temperature and groundwater temperature were used to calibrate the 1D numerical model. The implications of this study will be understanding the freezing and thawing of soil on groundwater recharge rate and how recharge rate may change from one year to the next in the sub-Arctic environment.