Assessing and predicting hydro-biogeochemical dynamics in the Weihe River basin in a shifting climate

The intricate interplay between hydrological and biogeochemical cycles underpins the sustainability of watershed resources, making it essential to comprehend their climate responses for adaptive strategies. Although climate change significantly influences the dynamics of the water-carbon cycle, understanding hydro-biogeochemical responses to climate change remains limited. In this study, we utilized the coupled hydro-biogeochemical model (SWAT-DayCent), known for its robust simulation of hydrological and biogeochemical processes, to evaluate how climate change influences water-carbon dynamics in the Weihe River Basin (WHRB), the largest tributary of the Yellow River. We further predicted the hydro-biogeochemical consequences using climate scenarios derived from four General Circulation Models under three Representative Concentration Pathways (low, medium, and high emissions pathways), with uncertainty analysis of future predictions. The results indicate that the net primary productivity (NPP) would rise under low and medium emissions pathway scenarios with rising temperatures and precipitation. Moreover, the WHRB shows that NPP and soil organic carbon (SOC) are more prominent in the southern parts and less in the northern parts. It is noteworthy that the continued air temperature rise could trigger a decline in SOC in the late century (2070–2099) under the high emissions scenario, though slight increments in precipitation and NPP might partially counterbalance this adverse effect. In summary, this study highlights the need for adaptive management strategies, especially under high emission scenarios, where rising temperatures may diminish SOC, necessitating policies that could enhance soil carbon sequestration and mitigate adverse climate impacts.