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Volume 12 (1999)
- Issue 6 Pages 455-
- Issue 5 Pages 361-
- Issue 4 Pages 283-
- Issue 3 Pages 203-
- Issue 2 Pages 95-
- Issue 1 Pages 1-
Volume 12, Issue 2
Displaying 1-10 of 10 articles from this issue
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[in Japanese]1999 Volume 12 Issue 2 Pages 95-96
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
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Katsushige SHIRAKI1999 Volume 12 Issue 2 Pages 97-108
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSIn this study, the author attempted to simulate the long-term discharge and the soil water content profile using a vertical two-dimensional numerical simulation method based on Richards'equation and to compare the results with observed data at a slope lysimeter which is covered with stones, 3 m wide, 6 m long, 2.5m in soil depth, and having a 20-degree slope. An upstream method that restricts numerical oscillation for the space direction and a modified Picard method were used to calculate Richards'equation. The evaporation loss from the surface of the lysimeter was calculated explicitly by regarding the evaporation as the boundary flux between the surface control volume and the atmosphere. The results show that the discharge, the soil water content profile, and the two-dimensional water flow in the lysimeter can be simulated continuously from very dry conditions to the wet conditions and from wet conditions to dry conditions. The calculated results of being very dry agree poorly with the observed data. The soil water retention function used to simulate the profile of the soil water pressure head well had characteristics similar to the observed data.View full abstractDownload PDF (4697K) -
Fumio YOSHINO1999 Volume 12 Issue 2 Pages 109-120
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSThe global warming affects global hydrologic circulation. The effects on annual runoff may be reflected on the variation of long-term annual runoff series. The report studies the tendency of variation and the spatial correlation of the long-term annual runoff series in 161 observation stations from 108 rivers in the world. The study shows that:(1) Annual runoff at the rivers in Sahel region show the reducing tendency from 1960's but annual runoff at several rivers in North America and west Europe show weak increasing tendency in 1970's and 1980's. It is uncertain that this result may reflect any effects of climatic change.(2) The coefficient of variations of annual runoff during 1961-1990 become larger than that during 1931-1960 in several arid or semi-arid regions in the world.(3) The coefficient of variation of annual runoff is, in general, negatively correlated with the mean annual runoff. The relation is affected by drainage area of the rivers.(4) The correlation coefficients between two observation stations selected from 108 rivers is very low, except the cofficients between upstream and downstream stations of the same rivers and between stations in adjacent rivers.View full abstractDownload PDF (648K) -
Masashi SHIMADA1999 Volume 12 Issue 2 Pages 121-129
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSAn approach to hydrograph separation based on daily discharges in rivers is proposed to identify both groundwater and the other components with the wavelet multi-resolution analysis (MRA). The new approach decomposes hydrograph into local discharges components of different frequency levels, and reconstructs significantly the components. The approach includes two concepts, the base as the direct component of groundwater and the distribution rate as the contributing ratio of the wavelet components of different frequencies to groundwater component. Through superposing part of lower frequency components to the base, groundwater component is reconstructed owing to the fact that much preevent rain(groundwater)contributes to faster components such as interflows.View full abstractDownload PDF (419K) -
Ichiro TAMAGAWA1999 Volume 12 Issue 2 Pages 130-138
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSThe effects of corrections for temperature and for humidity are studied in the context of the flux measurement with the eddy correlation method, based on the observed data. Corrections for cross wind and humidity effects to the temperature measured by the sonic anemometer-thermometer, and dynamic calibration and the correction for the low frequency unstability for the humidity measured by the infrared hygrometer are surveyed. The correlations for temperature are needed to avoid systematic overestimate of sensible heat flux. The dynamic calibration for infrared hygrometer is absolutely necessary, now. The correction for the low frequency is important only for the extreme conditions.View full abstractDownload PDF (1167K) -
Using Column-experimentNao FUKUNAGA, Masakazu SUZUKI, Takehiko OHTA1999 Volume 12 Issue 2 Pages 139-147
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSThe effects of carbon dioxide concentration in soil pore generated by soil respiration on water chemistry in the vertical infiltration process were examined using a column experiment with gas circulation and a steady rainfall supply system. The differences in percolated water quality between 10 percent (100, 000ppm) and atmospheric (400ppm) concentration columns which percolated through Toyora standard sand of 30cm in depth were observed in five chemical species :1) EC, 2) Ca2+, Mg2+ K+, 3) SiO2, 4) RpH, and 5) HCO3-at measuring RpH. The interrelations of these changes are as follows:a) Cations (Ca2+, Mg2+, K+), SiO2and HCO3-are released with increase of concentrations of soil CO2, b) Cations (Ca2+, Mg2+, K+) and HCO3-increase and raise EC, andc) H+decreases with increase of HCO3-, and RpH increases. Cations, SiO2and HCO3-, whose release are promoted by high CO2concentration at the same time, correspond to products of chemical weathering of silicate rock.View full abstractDownload PDF (3153K) -
Tadashi HIBINO, Hiroichi THURUYA1999 Volume 12 Issue 2 Pages 148-158
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
JOURNAL FREE ACCESSDistinct seasonal patterns can be observed for the meteorology of Japan. During summer the Ogasawara high pressure system develops over the Pacific Ocean. In winter season, the Siberian high pressure system develops over the Asian continent. As the Siberian high pressure system is the highest one in the world, the atmospheric pressure along the coast of Japan is higher in winter than in summer. With this variation of pressure arrangement, the sea level along the coast starts to rise in spring and starts to descend in Autumn. The Oyashio ocean current is influenced by these sea level variations which have a stronger effect on Japanese coastal waters in summer than in winter. The Oyashio current has low salinity and one of its impacts is to cause salinity in Ohfunato Bay (Sanriku) to be relatively low in summer and high in winter. The present study describes the relationship between atmospheric pressure and sea level in various ports along Japanese coasts.View full abstractDownload PDF (15540K) -
[in Japanese]1999 Volume 12 Issue 2 Pages 159-167
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
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[in Japanese], [in Japanese]1999 Volume 12 Issue 2 Pages 168-176
Published: March 05, 1999
Released on J-STAGE: February 10, 2010
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]1999 Volume 12 Issue 2 Pages 177-189
Published: March 05, 1999
Released on J-STAGE: October 22, 2009
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