5:15 PM - 7:15 PM
[AHW27-P11] Assessment of Dissolved Inorganic Phosphorus Loading in a Human-Impacted Catchment Using Weekly-based Modeling Approaches
Keywords:Non-Point Source Pollution, Phosphate, Human impact, Osaka Bay
Over the past few decades, while remote sensing technology has significantly enhanced the ability of catchment models to reproduce spatial patterns, improvements in temporal resolution have been limited. This limitation often forces researchers to rely on monthly-based water-quality modeling due to insufficient observational data for daily time steps, potentially underestimating peak nutrient loads during rainfall events. Osaka Bay, part of the Seto Inland Sea and known for its poor water quality, highlights this challenge. Among the major rivers flowing into the bay, the Yamato River exhibits the worst water quality. Despite improvements in sewage treatment facilities, reducing domestic and industrial wastewater discharge, non-point source (NPS) pollution from agriculture remains a growing concern, particularly as climate change intensifies through rising temperatures and more frequent intense rainfall events. To address these challenges, the Soil and Water Assessment Tool (SWAT), a catchment-scale hydrological model, was used to estimate dissolved nutrient loads in the Yamato River catchment using weekly water-quality observation data. The study revealed two key findings: first, a weekly-based model outperformed monthly-based models in capturing peak nutrient values influenced by weather conditions; second, agricultural activities were identified as the primary source of phosphorus pollution, with future climate change likely exacerbating phosphorus effluent from rice fields. This underscores the urgent need for high-temporal accuracy modeling to better understand and mitigate the impacts of climate change on water quality in vulnerable regions like Osaka Bay.