Predictive modelling of the movement of pollutants of the Naryn River using the SWAT+ model

The relevance of the study is conditioned by the need to assess the ecological state of the Naryn River basin under the influence of anthropogenic pollution and climatic changes caused by mining, agricultural runoff, urbanisation, and accumulation of sediments below hydroelectric power plants. The purpose of the study was to quantify the degradation of water quality and ecosystems in the Naryn River basin under the influence of anthropogenic pollutants and climate change. Methods of monitoring data analysis and mathematical modelling were used to achieve the goal. The results showed a significant decrease in biodiversity by 10-20% and water quality caused by an increase in concentrations of heavy metals – lead (up to 0.053 mg/l) and phosphorus (up to 0.48 mg/l) by 2050 under a high-emission climate scenario. It was found that erosion increased to 460 t/km2/year, and the productivity of the transboundary Syrdarya River decreased by 11%, which highlights the vulnerability of mountain and aquatic ecosystems. In addition, a decrease in the dissolved oxygen content to 4.7 mg/l was recorded, which increases the negative impact on aquatic biocoenoses. There was also an 18% decrease in the reproduction of fish populations, which indicates serious risks for their survival in conditions of habitat fragmentation below hydroelectric power plants. The practical significance of the study was to provide a framework for developing measures for monitoring and managing water resources in the region, which can be used by government authorities in Kyrgyzstan and neighbouring Central Asian countries, such as Kazakhstan and Uzbekistan, to coordinate transboundary water use, and environmental organisations and local communities for the conservation of biodiversity and sustainable development of the Naryn River basin