Environmentally oriented design of hydraulic structures taking into account the migration of aquatic organisms, water quality and sediment management in channel systems

Abstract

The design of hydraulic structures is characterized by a transition to ecologically oriented solutions, in which migratory permeability for aquatic organisms, transformation of water quality, and sediment balance in channel systems are regarded as interconnected components of a single natural-technogenic system. Channel damming creates barriers for anadromous and catadromous fish species, disrupting migration routes to spawning and feeding grounds. Analysis of field data from various designs shows that nature-like bypass channels achieve an average passage efficiency of 61,5%, significantly outperforming vertical-slot fish ladders, which demonstrate 38,7%, with statistically significant differences and a positive correlation between water discharge through the passage and migration success up to a threshold of 3,5% of the total flow. Transformation of hydrochemical parameters in tailwaters manifests in temperature deviations of up to 6.7 degrees Celsius with bottom releases without selective intake, dissolved oxygen deficiency, and gas supersaturation exceeding 127 percent with surface discharges, leading to stress in hydrobionts and gas bubble disease; however, the application of multi-level water intakes, aeration chambers, and cascade aerators reduces these anomalies several-fold, ensuring a water quality index of up to 0.87. Sediment management through flushing releases, bypass tunnels, and combined strategies reduces the retention coefficient from 94,7 to 47,3%, limiting channel incision to 0,29 meters per decade and preserving the granulometric composition of alluvium with an increased proportion of coarse fractions, thereby preventing degradation of floodplain habitats and erosion of structure foundations. Integration of these aspects into a comprehensive ecological efficiency index, with weighting coefficients verified by the analytic hierarchy process, enables evaluation of design alternatives, where the full set of measures achieves a value of 0.83 compared to 0.17 for the baseline scenario without environmental components, revealing synergistic effects and nonlinear dependencies that explain up to 81,2% of the variance through factor analysis. Numerical three-dimensional modeling of turbulent flows based on the Navier-Stokes equations, statistical processing of data from forty-seven sites, and correlation-regression analysis demonstrate that the systemic combination of measures for migration, water quality, and sediments substantially outperforms isolated approaches, contributing to the preservation of biological productivity, morphological stability, and hydrochemical equilibrium in regulated watercourses. This methodological approach opens prospects for quantitatively grounded design adapted to specific hydrological, morphological, and biological conditions and serves as a foundation for minimizing irreversible impacts on river ecosystems in the context of sustainable water management.