Search

Your search keyword '"Onda, Yuichi"' showing total 27 results
Start Over Author "Onda, Yuichi" Journal hydrological processes
27 results on '"Onda, Yuichi"'

4. Effectivity of dissolved SF6 tracer for clarification of rainfall–runoff processes in a forested headwater catchment.

Author

Sakakibara, Koichi, Tsujimura, Maki, Onda, Yuichi, Iwagami, Sho, Sato, Yutaro, and Nagano, Kosuke

Subjects
RAINFALL, RUNOFF, STABLE isotopes, FLOODS, SULFUR hexafluoride
Abstract

Understanding rainfall‐runoff processes is crucial for prevention and prediction of water‐related natural disasters. Sulfur hexafluoride (SF6) is a potential tracer, but few researches have applied it for rainfall‐runoff process studies. We observed multiple tracers including SF6 in spring water at 1‐ to 2‐hr intervals during rainstorm events to investigate the effectivity of SF6 tracer in rainfall–runoff studies through the clarification of rainfall–runoff process. The target spring is a perennial spring in a forested headwater catchment with an area of 0.045 km2 in Fukushima, Japan. The relationship between the SF6 concentration in spring water and the spring discharge volume was negative trend; the SF6 concentration in spring water becomes low as the spring discharge volume increases especially during rainstorms. The hydrograph separation using SF6 and chloride ion tracers was applied for determining the contribution of principal sources on rainfall–runoff water. It suggested more than 60% contribution of bedrock groundwater at the rainfall peak and high percentage contribution continued even in the hydrograph recession phase. Based on observed low SF6 concentration in groundwater after heavy rainfall, the replacement of groundwater near the spring with bedrock groundwater is indicated as a mechanism for water discharge with low SF6 concentration during rainfall events. Consequently, rainstorm events play an important role as triggers in discharging water stored in the deeper subsurface area. In addition, SF6 tracer is concluded as one of the strongest tracers for examining rainfall–runoff process studies. And, therefore, this study provided new insights into the dynamics of groundwater and its responses to rainfall in terms of SF6 concentration variance in water in headwater regions. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

26. Characterizing the flush of stream chemical runoff from forested watersheds.

Author

Zhao Zhang, Fulu Tao, Peijun Shi, Wei Xu, Yu Sun, Fukushima, Takehiko, and Onda, Yuichi

Subjects
WATERSHEDS, RUNOFF, WATER chemistry, CHEMICALS, PARAMETER estimation, FORESTED wetlands
Abstract

The article presents a study which examines the connections between watershed and flush parameters and determines whether flush exists at both the seasonal and event levels. The study quantifies three parameters that describe the characteristics of the flush and investigates flush characteristics of chemicals from four forested watersheds in Japan at both seasonal and event scales. Results show that the flush characteristics are complicated and depended on the elements of the hydrochemistry.

Published
2010
Full Text
View/download PDF

27. Estimation of suspended sediment sources using 137Cs and 210Pbex in unmanaged Japanese cypress plantation watersheds in southern Japan.

Author

Mizugaki, Shigeru, Onda, Yuichi, Fukuyama, Taijiro, Koga, Satoko, Asai, Hiroki, and Hiramatsu, Shinya

Subjects
SUSPENDED sediments, WATERSHEDS, GAMMA ray spectrometry, SEDIMENTS, SPECTRUM analysis, SPECTROMETERS, CESIUM, LEAD, ALKALI metals
Abstract

The article presents an estimation of suspended sediment sources with the use of 137Cs and 210Pbex in unmanaged cypress plantation watersheds in southern Japan. The 137Cs and 210Pbex were detected with the use of gamma-ray spectrometry in the surface soil of forest floor, stream bank and others. The multivariate sediment-mixing model that use 137Cs and 210Pbex showed that the contribution of the forest floor changes in various subwatersheds. Results show that the forest floor should be recognized as a source of suspended sediment in unmanaged cypress plantation watersheds.

Published
2008
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results