Abstract
The article presents an assessment of the reliability of hydraulic structures based on the analysis of long-term annual runoff. It was established that the use of only mean annual runoff characteristics leads to a significant underestimation of flood risks; therefore, maximum daily discharges were additionally analyzed in this study. The hydrological data from the Bolshaya Arna –Ulanbel hydrological station on the Shu River were used as the calculation basis, reflecting the combined effects of basin-scale runoff transformation, flow regulation, and water management activities in the lower reaches of the river. Based on long-term observation series for the period 1967–2022, a statistical analysis of annual runoff characteristics was performed, including mean, minimum, and maximum water discharges for different exceedance probabilities.It was established that high interannual variability and pronounced asymmetry of the runoff distribution lead to increased hydrological loads on hydraulic structures during high-flow years and create risks of water resource deficits during low-flow periods. The results demonstrate that the analysis of annual runoff can be effectively applied to assess the reliability, safety, and operating conditions of hydraulic structures, as well as to substantiate design and operational decisions.