Among the total of 17,764 agricultural reservoirs in Korea, KRC manages 3,324 agricultural reservoirs and the remainder come under the direct control of the municipalities. The ability of the agricultural reservoir supply is being rapidly decreased in many areas due to the indraft of a sedimentation as well as the deterioration of structures. In comparison with the initial ability of the agricultural reservoir supply, It was found that 88 percent of them built prior to the 1970s has a marked change caused by a drainage basin-condition, including a change of the command area and a sedimentation. This study, Analysis on ability of the agricultural reservoir supply, takes 2,673 agricultural reservoirs as a research target which are under management of KRC and have their own catchment area and command area. The main object are to estimate the water supply potential of reservoirs used for agricultural purpose and to understand the optimum water supply levels of them.