The quick response of groundwater discharge to a rain storm is a serious social problem in Korea, because the drastic change in river flow occurs during storms owing to thin soils and weathering zones of granitic rocks typical in Korea. A series of undisturbed soil-column experiments was operated to make clear the mechanism of subsurface water discharge influenced by pore air behavior. A layered granitic soil (A-Horizon, B-Layer and Saplorite) was taken from a hill located 55 km south of Seoul City, and was used for the column experiments as a well-reflection material of the field phenomenon. In the experiments, artificial rainfall intensity (10, 20, 30 and 40 mm/h) was established, and the pore air pressure in the soil, the pressure head of soil water, and the discharge rate of groundwater from the bottom of the experimental column were measured. The experiments provided interesting results as follows: (1) water movement in the layered soil was controlled by the pore air pressure even in the 10 mm/h rainfall,; (2) under the rainfall intensity of 20 mm/h, the pore air made a first peak in the discharge with a quick response to the rainfall because of the pre-event water discharge which had been maintained in the lower part of the soil,; and (3) the rainfall intensity of 40mm/h supplied a boundary condition of the runoff process based on the pressure transport in the field.
It is known that Lake Meike located near the top of Mt. Yatsugatake is one of the most sensitive lakes to acid deposition in Japan; the mean value of lake water alkalinity is about 24μeq ℓ-1. The primary objects of this study were to identify the load of chemical characteristics to lake and the circulation of chemical components in watershed. Samples were collected from August 1997 to October 1998 (excluded winter seasons), and analyzed major ionic concentrations (Cl-, NO3-, SO42-, Na+, K+, NH4+, Mg2+, Ca2+ and Alkalinity). The results showed that chemical components of lake water were characterized by Na++K+ and HCO3-, and the concentrations were similar to that of precipitation. Water balance was calculated. Input was equal to precipitation volume. Twenty-seven percents of precipitation was lost by evapotranspiration, 73% was lost by exudation through infiltration. In Lake Meike watershed, it was estimated that Cl-, SO42-, Na+, Mg2+ and Ca2+ were flowed out from watershed into lake, NO3-, NH4+ and K+ were consumed and/or accumulated in watershed. But these results suggested that amount of ionic components supplied from the catchment were very few.