Current Quality of Water in the Ivankovskoye Reservoir According to Indicators Limiting the Development of Hydrobionts

A comprehensive assessment of the ecological status of the Ivankovskoye Reservoir (European Russia) was conducted for the 2017–2022 period, focusing on hydrochemical parameters and anthropogenic impacts. The study analyzed key water quality indicators: dissolved oxygen, pH, ammonium nitrogen, nitrites, nitrates, phosphates, BOD5, and total iron. Sampling was performed at 18 stations across four reservoir sections (Shoshinsky, Upper Volga, Middle Volga, and Lower Volga) using standardized methods (PND F). The water pollution index (WPI) was applied for integrated water quality assessment, and anthropogenic load was calculated using Frumin’s formula. Results revealed seasonal dynamics of oxygen regime: summer oxygen depletion in bottom layers (down to 1.15 mg/dm³) was linked to thermal stratification and organic matter decomposition. Exceedances of maximum permissible concentrations (MPC) were recorded for ammonium nitrogen (up to 1.5 × MPC), nitrites (up to 4.7 × MPC), BOD5 (up to 2 × MPC), and iron (up to 7.7 × MPC). The Shoshinsky section exhibited the highest pollution levels due to eutrophication and low water exchange. Average WPI values (1.16–1.33) corresponded to Class 3 water quality (moderately polluted). Key pollution sources included discharges from the Konakovskaya GRES power plant, agricultural runoff, and recreational activities. Despite the ban on industrial fishing (since 2007), no water quality improvements were observed, and anthropogenic pressure continued to rise (index 1.87 in 2021 vs. 2005–2017 data). The study emphasizes the need for enhanced measures to reduce nutrient and chemical loads, particularly under climate change and increasing anthropogenic pressure. The findings may inform water resource management strategies and ecological restoration programs for the reservoir.

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