[A-HW24] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW24-P15] Quantitative evaluation of water and nutrient discharge by a hydrological model in the sub-catchments of Osaka Bay

*Kawaguchi Tomoya¹, Mitsuyo Saito², Kunyang Wang³, Shin-ichi Onodera⁴ (1.Faculty of Environmental Science and Technology, Okayama University, 2.Graduate School of Environmental and Life Science, Okayama University, 3.Graduate School of Integrated Arts and Sciences, Hiroshima University, 4.Graduate School of Advanced Science and Engineering, Hiroshima University)

Keywords:SWAT model, Sub-catchments of Osaka Bay, water and nutrient discharge

In this study, Soil and Water Assessment Tool (SWAT) was applied to the Saho River and Akishino River, which are the sub-catchments of Yamato river flowing into Osaka bay, and constructed a model to estimate daily discharges of water and nitrate. We also evaluated the spatial characteristics of nitrate discharge in sub-catchment and hydrological response unit (HRU) scales using this model. The results suggest that agricultural area, mainly paddy fields and untreated waste water are the major loading sources of nitrate in the target catchment where approx. 90% of the area is covered by seawage treatment system. It also indicate the effectiveness of sewage treatment system for reducing the nitrate loading.

Acknowledgement: This research was supported by Research promotion for the environmental creation and rehabilitation of Osaka Bay area by Osaka Bay Regional Offshore Environmental Improvement Center (No. 010005, 020004, 030003, PI: Mitsuyo Saito) and APN project (No CRRP2019-09MY-Onodera, PI: Shin-ichi Onodera).