Exploring dynamics of riverine phosphorus exports under future climate change using a process-based catchment model

Summary

A quantitative understanding of riverine phosphorus (P) export in response to shifts in anthropogenic inputs, terrestrial retention, and climate is important for developing mitigation measures at a watershed scale. In this study, we simulated a decadal change in the riverine P export in a human-dominated watershed from a cold climatic region located in Northeast Asia. A process-based catchment model nested within a delicate land P module was applied to simulate the dynamics of P retentions and its exports in the watershed. We found that the terrestrial P retention capacities declined for 2008–2017, and the decline rates would accelerate under three representative concentration pathways (i.e. RCP2.6, RCP4.5 and RCP8.5). The P released from the diffused source and historical legacy could partly offset the effort through point-source P reduction by the improved wastewater treatments. Climate changes (e.g., duration and frequency of extreme rainfall event) could accelerate P deliveries from the P legacy retained in soils. We suggest that a long-term watershed P management strategy should be targeted to reduce historical P legacy input into river rather than solely focusing on the short-term changes in the riverine P concentration.