Water resources in Korea were estimated at about 114 billion ㎥ calculated from 1,159㎜ of the mean precipitation per year precipitation of forest land covered 66% of whole area of country is equivalent of 75.24 billion ㎥. Project for water storage was estabilished and carried out at river and watercourses to keep water resources. However, it was not achieved on the research of forest as the source of water resources. These studies were carried out to know the amount of precipitation, evaporation loss, soil moisture, surface water and subsurface water at Seoul, Kwangnung, and Yagju from 1975 to 1984. 1. Average precipitation of 3 stations in a year is 12.808 ㎥ per hectar, however, average precipitation of Kwangnung averaged 13,955 ㎥. Increase of 9% of precipitation at Kwangneung in comparison with three stations seems to be the effect of good forest. 2. The amount of evaporation at forest land was estimated at 1,200㎥ per hectars calculated with coefficient 0.13 by Brooks at Kwangneung evaporation. The transpiration of stands is 2,468㎥ per hectar by the calculation (P-I-EV) 3. The amount of crown interception is 2,562㎥ per hectar by the interception 20% of precipitation per year. 4. The whole run off by 51.4% precipitation is 6,578㎥ per hectar a year. 5. Storage water in the soil is 2,468㎥ per hectar a year (So=P-R-I). 6. Usually soil water holding of surveyed place is 15-20% of soil volume in comparison with 40% water of maximum holding capacity. The change of soil water mainly ocurred in 30㎝ depth soil but it do not occurred in 60㎝ depth so soil water holding capacity has largely shallow horizon soil. 7. The litter of stand was estimated at 90% of amount weight of water retaining and it had very important role to increase of soil water and had indirectly effect by the improving of soil structure with the humus. 8. Water balance of forest is the following diagram.