Quality Control of Redundant Water Level Gauges in South Korea River Gauging Stations

In South Korea, river stage gauging stations operate redundant water level gauges to mitigate instrument malfunctions and anomalous measurements. Currently, redundant gauges are installed at over 60% of gauging stations, reflecting their widespread implementation; however, their quality management and practical utilization remain limited. In many cases, installation and operational conditions are not fully accounted for in observed water levels, leading to significant discrepancies between primary and redundant gauges. These discrepancies may arise from river characteristics, artificial configuration errors, or site-specific conditions. This study investigates the causes of discrepancies between primary and redundant gauges and proposes appropriate correction methods. Anomaly detection was first conducted on redundant gauge measurements using limit tests, duration tests, and regression tests to ensure data reliability. Based on this, the relationships between primary and redundant gauge readings were analyzed using simple regression, multiple regression, and nonparametric LOESS (Locally Estimated Scatterplot Smoothing) regression. These procedures not only facilitated the derivation of site-specific correction methods but also supported the preliminary development of a real-time quality control program, moving beyond conventional manual, non-real-time quality management. Nevertheless, because the causes of discrepancies and installation conditions vary by site, site-specific correction strategies are required, and ongoing monitoring and refinement of measurements and corrections remain necessary. Furthermore, real-time utilization of redundant gauges is challenging at newly established stations. Despite these limitations, the proposed correction strategies have the potential to go beyond simple substitution of primary gauge readings, enabling higher-quality hydrological data production and improved quality control. These strategies are expected to enhance real-time hydrological monitoring systems and strengthen the reliability of national hydrological data management frameworks.Keywords : Redundant, Water Level Gauging, Uncertainty, Operational Monitoring AcknowledgementsThis work was supported by Korea Environment Industry & Technology Institute(KEITI) through Research and Development on the Technology for Securing the Water Resources Stability in Response to Future Change Project, funded by Korea Ministry of Climate, Energy, Environment(MCEE)(RS-2024-00332300).