Hydrogeological Structure and Groundwater Flow of Alluvium in the South Sarobetsu Moor

Abstract

 The cross-sectional modeling of groundwater flow was carried out with the help of geological surveying, piezometer monitoring, and the chemical composition estimation of groundwater to investigate the groundwater flow system in the alluvial plain in Sarobetsu moor located in the northern part of Hokkaido. According to the previous studies, the geology of the alluvium is mud-rich. The Ho-la stratum (clay layer), which was deposited during the Hypsithermal age, had low permeability. The observation of the hydraulic head and chemical composition of the groundwater indicated that the Ho-la stratum inhibited vertical groundwater flow. In addition, the highest hydraulic head was measured at the basement rock in the eastern part of the moor and hydraulic heads were found to decrease in shallow areas and in the western part of the moor. The highest hydraulic head was guessed to have formed on account of tectonic movements. The distribution of the highest hydraulic head was estimated by analysis use with the groundwater flow model.