Abstract: Quantitatively analyzing changes in the pollution bearing capacity of rivers under varying hydrological and water quality conditions holds significant practical importance for water resource protection and pollution control within a basin or region. This study focuses on the Sanduizi-Lazha section of Panzhihua City, located at the tail of the Wudongde Reservoir on the Jinsha River. We examined the impact of hydrological and water quality conditions on ammonia nitrogen bearing capacity of the river reach. Results indicate that when the flow rate at Sanduizi section ranges from 900 to 2 000m³/s, and ammonia nitrogen concentrations range from 0.10 to 0.50 mg/L, the ammonia nitrogen bearing capacity in this section varies from 235.12 to 4 670.38 t/a. Changes in flow rate and ammonia nitrogen concentration in the Sanduizi section show a linear correlation with ammonia nitrogen bearing capacity. Specifically, under low flow rates and ammonia nitrogen concentrations, the comprehensive variation in ammonia nitrogen bearing capacity ranges from 0.86 to 64.23 t/a, with hydrological factors predominantly influencing these changes. Conversely, under high flow rates and ammonia nitrogen concentrations, the comprehensive variation ranges from -105.34 to -1.84 t/a, with water quality factors primarily driving these variations. These findings offer insights and guidance for water resource protection and pollution control strategies within river basins or regions.

Key words: pollution bearing capacity, hydrological and water quality conditions, water resources protection, water pollution control, Wudongde Reservoir