Estimation of groundwater exfiltration with environmental tracers in extensive irrigated paddy areas and reducing model uncertainties

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K18774
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Rural environmental engineering/Planning
• Research Institution: National Agriculture and Food Research Organization
• Principal Investigator: Yoshida Takeo 国立研究開発法人農業・食品産業技術総合研究機構, 農村工学研究部門, 主任研究員 (80414449)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: 流域水循環 / 水田灌漑 / 環境同位体 / 地表水・地下水交流

Outline of Final Research Achievements

Water flows in watersheds containing extensive areas of irrigated paddies are complex because of the substantial volumes involved, and the repeated cycles of water diversion from, and return to, streams. Numerous studies have attempted to quantify the surface water-groundwater interactions using the stable isotopes of water; however, the temporal variation in these isotopic compositions due to fractionation during evaporation from water surfaces hinders their application to watersheds with extensive irrigated paddies. Our study shows how surface water-groundwater interactions can change 87Sr/86Sr along river reaches; and the continuous decline in the 87Sr/86Sr along the stream suggests an discharge of water from the shallow aquifers. The water samples in the Gogyo River during the non-irrigated period were lower in 87Sr/86Sr and higher in Sr concentrations, suggesting an increase in relative contributions of the water from the shallow aquifers during the non-irrigated period.

Free Research Field

水文学