17:15 〜 18:30
[AHW22-P13] Analysis for the characteristics of water and nutrient discharge in a sub-basin of Osaka Bay catchment
キーワード：都市化流域、水・栄養塩流出
Quantitative evaluation of nutrient discharge in watersheds is important for taking measures of environmental management of enclosed coastal seas. The hydrological model approach is a powerful tool for the evaluation of the impacts of climate change (e.g. extreme rainfall) and human activities (e.g. land-use change) on water and nutrient discharge in watersheds. We aimed to analyze the characteristics of water and nutrient discharge in the Saho River which is a sub-basin of Yamato River catchment inflowing Osaka Bay, western Japan.
The results are as follows;
(1) We applied SWAT (Soil & Water Assessment Tool) to Saho River catchment and succeeded in the model construction for estimating water discharge on an hourly basis considered the effects of flooding.
(2) We also constructed a daily basis nutrient discharge model that considered the water discharge fluctuations during floods with high reproducibility.
(3) We simulated how the catchment water balance will change assuming that all of the current paddy fields and farmland will change to residential areas due to urbanization by the developed hourly basis discharge model. In this simulation, the baseflow will decrease by 0.1 m3/s on average, while the peak flow rate during floods will increase by 1.7 m3/s at maximum. The results suggest the increased risk during floods.
(4) Simulated nitrate-nitrogen inflow from Saho River to Yamato River by the developed daily basis nutrient discharge model was 261 kg/day on average during baseflow periods, 1.5 tons/day at the maximum during floods, and 94.7 tons/day in the annual, respectively.
*This work is supported by the research grants of “Environmental Rehabilitation and Creation of the Osaka Bay Area, 010005, 020004, 2019-2020, PI: Mitsuyo SAITO” and “Asia-Pacific Network for Global Change Research, CRRP2019-09MY-Onodera, 2019-2022, PI: Shin-ichi ONODERA”.
The results are as follows;
(1) We applied SWAT (Soil & Water Assessment Tool) to Saho River catchment and succeeded in the model construction for estimating water discharge on an hourly basis considered the effects of flooding.
(2) We also constructed a daily basis nutrient discharge model that considered the water discharge fluctuations during floods with high reproducibility.
(3) We simulated how the catchment water balance will change assuming that all of the current paddy fields and farmland will change to residential areas due to urbanization by the developed hourly basis discharge model. In this simulation, the baseflow will decrease by 0.1 m3/s on average, while the peak flow rate during floods will increase by 1.7 m3/s at maximum. The results suggest the increased risk during floods.
(4) Simulated nitrate-nitrogen inflow from Saho River to Yamato River by the developed daily basis nutrient discharge model was 261 kg/day on average during baseflow periods, 1.5 tons/day at the maximum during floods, and 94.7 tons/day in the annual, respectively.
*This work is supported by the research grants of “Environmental Rehabilitation and Creation of the Osaka Bay Area, 010005, 020004, 2019-2020, PI: Mitsuyo SAITO” and “Asia-Pacific Network for Global Change Research, CRRP2019-09MY-Onodera, 2019-2022, PI: Shin-ichi ONODERA”.