Currently, a vast amount of hydrologic data is accumulated in real-time through automatic water level measuring instruments in agricultural reservoirs. At the same time, false and missing data points are also increasing. The applicability and reliability of quality control of hydrological data must besecured for efficient agricultural water management through calculation of water supply and disaster management. Considering the characteristics ofirregularities in hydrological data caused by irrigation water usage and rainfall pattern, the Korea Rural Community Corporation is currently applyingthe Hampel filter as a water level data quality management method. This method uses window size as a key parameter, and if window size is large,distortion of data may occur and if window size is small, many outliers are not removed which reduces the reliability of the corrected data. Thus,selection of the optimal window size for individual reservoir is required. To ensure reliability, we compared and analyzed the RMSE (Root Mean SquareError) and NSE (Nash?Sutcliffe model efficiency coefficient) of the corrected data and the daily water level of the RIMS (Rural InfrastructureManagement System) data, and the automatic outlier detection standards used by the Ministry of Environment. To select t...