Assessing the impact of climate change on BMPs’ effectiveness in the Hanjiang River Basin, China

This study aims to investigate the impact of climate change on watershed Best Management Practices (BMPs). To achieve this, a SWAT model was developed for the Hanjiang River Basin, incorporating climate model data from CMIP6 under different climate scenarios (SSP2-4.5 and SSP5-8.5). Using 2000–2019 as the historical baseline, the study simulated and evaluated the effectiveness of 10 BMPs in reducing nitrogen and phosphorus loads from 2025 to 2100.The results indicate that future climate change will lead to significant increases in precipitation and temperature, which will, in turn, cause substantial increases in total nitrogen (TN) and total phosphorus (TP) loads, with intensified effects on a spatial scale. Under climate change scenarios, the effectiveness of BMPs in reducing surface runoff, soil loss, and nutrient loads generally declines. Specifically, BMPs’ effectiveness in reducing soil loss decreases by an average of 18.9 percentage points, while the reduction rate for TN load decreases by an average of 5.8 percentage points. Except for fertilizer reduction, which shows an improvement, other BMPs exhibit an average reduction of 3.1 percentage points in TP load reduction. Furthermore, this study explores how precipitation, temperature, and nutrient load levels influence BMP effectiveness. Increased precipitation and rising temperatures tend to weaken BMP performance, particularly for structural measures. In conclusion, we recommend that future management strategies fully consider the impact of climate change to enhance the adaptability and effectiveness of BMPs.