Spatially Explicit Assessment of Agricultural Water Equilibrium in Korea Peninsula

In agriculture, balance between water retention and water use is an issue handled in most region and crops. This study suggested agricultural water equilibrium (AWE) it a new assessing concept for management of agricultural water in spatially explicit. This concept based on the principle of supply and demand, to the usage of agricultural water, it is possible to define virtual water content of crops (VWC) as the demand, and cropland water budget (CWB) as the supply. For the assessing AWE of the Korean Peninsula, quantified by estimating the CWB based on the natural hydrological cycle and the VWC of rice, a key crop in the Korean Peninsula. Among five factors used to assess AWE, four factors except annual precipitation were estimated by using the GEPIC model, and calculated CWB and VWC at past three decade. AWE results over the past 30 years were computed by deducting VWC showing demands in croplands from CWB meaning water supply that result showed highly vertical difference of South and North Korea. When sorting AWE data by major river basin in the Korean Peninsula, most river basins in North Korea also showed very low level. The cause of making latitudinal change in AWE is the differences of VWC and CWB in terms of latitudinal change. Which can be explained by decoupling of agricultural water demand and supply. Identifying relation with AWE, VWC and CWB in concept of elasticity, elasticity of AWE following VWC was appeared as very low relatively and absolutely. And the elasticity of AWE following CWB is very good relatively and good absolutely. When VWC is inelastic, the relative elasticity of CWB tended to become very high. AWE values presented in the study were not absolute, though these values appeared enough in explaining the latitudinal change, demand and supply of agricultural water, and have been meaningful in establishing the concept of AWE.