Ground water level observaton in a slope of watershed consisted of Paleozoic sedimentary rocks

Abstract

An observation well with depth of 18 m was bored in a slope of watershed consisted of Paleozoic sedmentary rocks. The layer shallower than around 16 m is a crack rich weathered sandy mudstone, and the deeper layer is a little cracked sandy stone. Water permeability was stable with 10^-6 - 10^-5 order (cm/s) when ground water level (GWL) was less than -16m. It was less rainfall since August in 2007, GWL decreased lower than the bottom of well in mid October. Then, about one month later since rainfall over 60 mm observed in late March, GWL came back in the well. This recharge would not be derived from quick drain of rainfall because temperature of ground water kept about 14 deg.C during the observation period.