Abstract
Soil moisture in the No.1 Kamabuchi forested experimental watershed (area: 3 ha, altitude: 160-250 m) was measured using time domain reflectometry (TDR) through a year. The Kamabuchi forested experimental watershed is located on Mogami district of Yamagata prefecture where the climate is cool temperature zone with a lot of snows in winter. The watershed's land surface is blanketed over 1 m deep snow in an ordinary year.
Moisture Point (MP-917, Environmental Sensors Inc.) with a soil moisture profiling probe was installed in lower portion of hillslope facing northeast near the gauging weir of No.1 watershed. Five conductors, 15 cm long each, lined into the soil moisture profiling probe. The probe was vertically inserted into the soil; insertion limit caused by hardness of soil was 60 cm deep. Averaged soil water contents around each conductor were taken in 20 minutes intervals. Slope gradient was about 30 degree around the probe installed, and an altitude difference from the installed point to top of upper slope is about 13 m high.
Soil water contents (WC) in 0 to 30 cm deep increased after snow height covering land surface exceeded about 60 cm. Higher WC condition in 0 to 30 cm deep continued about two months, until mid thawing period. At the same period, WC in 30 to 45 cm deep gradually decreased. From the mid thawing period to end of thaw, WC in 0 to 30 cm deep rapidly decreased, but WC in 30 to 45 cm deep gradually increased. After the end of thaw, decreasing of WC in 0 to 60 cm deep continued until summer monsoon period which provides a lot of rainfall. From the summer monsoon through October, WC in 0 to 60 cm deep changed according to rainfall. It became known that increasing of WC by rainfall occurred in whole depth of soil, WC increasing under snow cover occurred mainly in subsurface layer of soil.
