HR: 1340h
AN: H23C-1435    [Abstracts]
TI: The behavior of entrapped air in the bedrock fracture and the implication of storm runoff mechanism
AU: * Onda, Y
EM: onda@atm.geo.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 305-8572 Japan
AU: Masuguchi, T
EM: s0323560@ipe.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 305-8572 Japan
AU: Tsujimura, M
EM: mktsuji@atm.geo.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 305-8572 Japan
AU: Furuya, A
EM: usasami@air.ocn.ne.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 305-8572 Japan
AU: Shimada, J
EM: jshimada@sci.kumamoto-u.ac.jp
AF: Faculty of Science, Kumamoto University, 39-1,Kurokami 2-chome, Kumamoto, 860-8555 Japan
AB: To study the effect of entrapped air in the bedrock fissures on runoff generation, field studies were conducted in Mamushi-dani watershed, Shiranui-town, Kumamoto Prefecture. Two bore holes, 25 m and 60 m in depth, were used to study the behavior of entrapped air in the bedrock fractures. We monitored air flow from bores, and air pressure in the boring wells, repeatedly. Also we have monitored soil suction by recording tensiometers and spring runoff by combination of a Parshall flume and a V-noch weir. The air in shallower bore, 25 m depth, respond quickly to the barometric pressure changes, but the deeper bore, 60 m depth, showed marked time lag to the barometric pressure changes. The_@observation of air flow rate due to barometric pressure changes in both bores enables us to calculate the effective fissures hydrologically connecting in the bedrock, which is found to be considerably large. During the heavy storm events, the soil surface became saturated and the surface ponding was observed. The air pressure in the bore holes became compressed, suggesting the entrapped air in the bedrock was compressed by surface ponding. The marked runoff peak was observed coinciding with the compression of air in the bedrock, suggesting that the compression of air in the bedrock may trigger the storm runoff.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1860 Streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: Fall Meeting 2005