The SiO₂ concentrations of rain water, through fall, unsaturated soil water, groundwater, spring water and streamwater were measured in a small forested watershed. SiO₂ is a soluble chemical substance which is comparatively contained in natural water. The results indicate the following points,
1) SiO₂ is not contained in rain water and stemflow.
2) SiO₂ is dissolved from soil mineral during the process of unsaturated vertical infiltration and temporary saturated lateral infiltration of soil water.
3) The SiO₂ concentration of groundwater settles into one value which is peculiar to each watershed (approximately 18 mg/l in the case of Kiryu experimental watershed) at saturated zone and dose not change during lateral movement of groundwater.
4) The SiO₂ concentrations of spring and stream water are approximately same as groundwater without the rain events accompanied with direct runoff which dilute the spring and stream water to cause the lower concentration of SiO₂.
Furthermore it was estimated that approximately from 14 to 16g/m² of SiO₂ per year is dissolved at surface soil and its boundary with bed rock and run off to stream in Kiryu experimental watershed.

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Evaporation from shallow lakes was estimated at 66 meteorological stations in Japan. The annual amount of evaporation is smaller at the station located in the lower latitude, being about 500mmy^-1 in northern Japan and about 700mmy^-1 in southern Japan. These values correspond to 30-50% of the annual amount of precipitation.
The annual solar radiation and effective longwave radiation range 130 to 160Wm^-2 and 50 to 70Wm^-2, respectively.

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Forest rainfall interception is estimated at 153 points in Japan. The annual amount of rainfall interception ranges 200 to 500 mmy^-1, which correlates closely with the number of precipitation days. It is shown that traditional measurements of the precipitation at one station outside of forests may have had large errors in past observations of rainfall interception.

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