Assessment of the impact of quarrying on navigable conditions in downstream of the Cheboksary hydroelectric complex

This study addresses the operation of unsupported hydroelectric facilities, including the Cheboksary hydroelectric complex, which can cause significant changes in the hydrological and channel regimes of the downstream sections, leading to progressive channel erosion and reductions in water levels. A comprehensive assessment is presented of the impact of non-metallic building material extraction on the channel morphology and navigable conditions of the Volga River between km 1187.0 and 1255.0 downstream of the Cheboksary hydroelectric complex. The methodology is based on two-dimensional mathematical modeling of sediment transport and flow characteristics using the Saint- Venant equation system in the FLOOD software package. Modeling was performed for two states of the channel: the actual (existing) and the design state (considering full quarry development). Results indicate that quarry development has a limited effect on the level regime. The Sidelnikovskoye field exerts the greatest influence on flow hydraulics, where current velocities along the navigable channel are reduced by half, and local bottom deformations are observed in some areas. Development of other fields causes reduced current velocities without inducing washouts, as the velocities in these areas remain below the calculated non-washout threshold. The analysis suggests that under current conditions, channel quarrying for the extraction of non-metallic building materials will not produce adverse effects, will not further reduce water levels, will not exacerbate channel erosion, and will not deteriorate navigable conditions in this section of the Volga River.