Subsurface water is generally divided into two major types; Phreatic water or Soil moisture in the unsaturate zone, and groundwater in saturated zone. This division is made mainly due to the difference in the physics of water flow in the saturated versus the unsaturated zone. Groundwater is stored in the interparticle pore spaces and cracks within rock material. Groundwater represents a massive water storage on Earth (About 40 percent of the groundwater on Earth is fresh water).
The concept of safe yield was evidently suggested early in the century. According to Todd(1959), ″The basin draft on ground water supply which can be continued indefinitely without harming the supply or basin landowners." The accurate estimation of safe yield is based on groundwater recharge. The popular techniques of groundwater recharge estimation include water table fluctuation method, baseflow separation method and annual water balance method.
The purpose of this research, estimation of safe yield in Sancheong catchment. Thus, the information of groundwater level data in Sancheong basin supplied by GiMS was used to examine the characteristics of usage of groundwater. Also, to calculate the safe yield, which is commonly used to make the usage plan of groundwater, NRCS method was applied for estimate the water recharge of Sancheong basin.