Greater Sustainability in the Future of Hanjiang River Under Climate Change: The Case of Nitrogen

Water resources are essential for human survival and sustainable development. However, the global freshwater scarcity, exacerbated by climate change, presents significant sustainability challenges. Using the SWAT model, we simulated the spatiotemporal distribution of total nitrogen (TN) in the Hangjiang River Basin from 2005 to 2020. The average TN concentration was 2.16 mg/L, with the soil nitrogen pool contributing 92.78% of emissions, highlighting the need to address the soil nitrogen legacy. Sampling showed average concentrations of TN, nitrate, ammonium, nitrite, and dissolved organic nitrogen at 3.01 mg/L, 1.66 mg/L, 0.21 mg/L, 0.02 mg/L, and 1.11 mg/L, respectively. Precipitation accounted for 61.4% of nitrogen emission variability, indicating that water resource sustainability will be significantly influenced by climate change. Projections indicated that from 2020 to 2050, climate change will increase runoff by 6.19 m 3 /s and reduce TN concentration by 0.004 mg/L annually, potentially enhancing the overall sustainability of water resources. It’s necessary to continue strengthening the prevention and control of agricultural non-point source pollution and reduce nitrogen discharge to further enhance water resource security for the Beijing–Tianjin–Hebei development. The findings provide critical insights to inform policies aimed at protecting water sources and ensuring public water safety.