Influence of bedrock groundwater on streamflow characteristics in a volcanic catchment          下载免费PDF全文

Masamitsu Fujimoto  Nobuhito Ohte  Masatoshi Kawasaki  Ken'ichi Osaka  Masayuki Itoh  Izumi Ohtsuka  Masami Itoh 《水文研究》2016,30(4):558-572

Groundwater movements in volcanic mountains and their effects on streamflow discharge and representative elementary area (REA) have remained largely unclear. We surveyed the discharge and chemical composition of spring and stream water in two catchments: the Hontani river (NR) catchment (6.6 km²) and the Hosotani river (SR) catchment (4.0 km²) at the southern part of Daisen volcano, Japan. Daisen volcano is a young volcano (17 × 10³ years) at an early stage of erosion. Our study indicated that deep groundwater that moved through thick lava and pyroclastic flows and that could not be explained by shallow movements controlled by surface topography contributed dominantly to streamflow at larger catchment areas. At the NR catchment, the deep groundwater contribution clearly increased at a catchment boundary defined by an area of 3.0 km² and an elevation of 800 m. At the SR catchment, the contribution deep groundwater to the stream also increased suddenly at a boundary threshold of 2.0 and 700 m. Beyond these thresholds, the contributions of deep bedrock groundwater remained constant, indicating that the REA is between 2 and 3 km² at the observed area. These results indicate that the hydrological conditions of base flow were controlled mainly by the deep bedrock groundwater that moved through thick lava and pyroclastic flows in the undissected volcanic body of the upper part of the catchment. Our study demonstrates that deep and long groundwater movements via a deep bedrock layer including thick deposits of volcanic materials at the two catchments on Daisen volcano strongly determined streamflow discharge instead of the mixing of small‐scale hydrological conditions. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Estimating snow distribution over a large area and its application for water resources     

So Kazama  Hirokazu Izumi  Priyantha Ranjan Sarukkalige  Takayuki Nasu  Masaki Sawamoto 《水文研究》2008,22(13):2315-2324

The spatial and temporal distribution of the snow water equivalent (SWE), snow density and snow depth were estimated by a method combining remote sensing technology and degree‐day techniques over a study area of 370 000 km². The advantages of this simulation model are its simplicity and the availability of degree‐day parameters, which can be successively evaluated by referring to snow area maps created from satellite images. This simulation worked very well for estimating SWE and helped to separate the areas of thin snow cover from heavier snowfall. However, shallow snow in warm regions led to some misjudgments in the snow area maps because of the time lag between when the satellite image was acquired and the simulation itself. Vulnerable areas, where a large variation in the amount of snow affects people's life, could be identified from the differences between heavy and light snow years. This vulnerability stems from a predicted lack of irrigation water for rice production caused by future climate change. The model developed in this study has the potential to contribute to water management activities and decision‐making processes when considering necessary adaptations to future climate change. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Effects of the introduction of rice on evapotranspiration in seasonal wetlands          下载免费PDF全文

Tetsuji Suzuki  Takeshi Ohta  Tetsuya Hiyama  Yasuhiro Izumi  Osmund Mwandemele  Morio Iijima 《水文研究》2014,28(17):4780-4794

Land use changes in wetland areas can alter evapotranspiration, a major component of the water balance, which eventually affects the water cycle and ecosystem. This study assessed the effect of introduced rice‐cropping on evapotranspiration in seasonal wetlands of northern Namibia. By using the Bowen ratio–energy balance method, measurements of evapotranspiration were performed over a period of 2.5 years at two wetland sites—a rice field (RF) and a natural vegetation field (NVF)—and at one upland field (UF) devoid of surface water. The mean evapotranspiration rates of RF (1.9 mm daytime^?1) and NVF (1.8 mm daytime^?1) were greater than that in UF (1.0 mm daytime^?1). RF and NVF showed a slight difference in seasonal variations in evapotranspiration rates. During the dry season, RF evapotranspiration was less than the NVF evapotranspiration. The net radiation in RF was less in this period because of the higher albedo of the non‐vegetated surface after rice harvesting. In the early growth period of rice during the wet season, evapotranspiration in RF was higher than that in NVF, which was attributed to a difference in the evaporation efficiency and the transfer coefficient for latent heat that were both affected by leaf area index (LAI). Evapotranspiration sharply negatively responded to an increase in LAI when surface water is present according to sensitivity analysis, probably because a higher LAI over a surface suppresses evaporation. The control of LAI is therefore a key for reducing evaporation and conserving water. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A new variant of saponite‐rich micrometeorites recovered from recent Antarctic snowfall     

Kanako SAKAMOTO  Tomoki NAKAMURA  Takaaki NOGUCHI  Akira TSUCHIYAMA 《Meteoritics & planetary science》2010,45(2):220-237

Abstract– Eight saponite‐rich micrometeorites with very similar mineralogy were found from the recent surface snow in Antarctica. They might have come to Earth as a larger meteoroid and broke up into pieces on Earth, because they were recovered from the same layer and the same location of the snow. Synchrotron X‐ray diffraction (XRD) analysis indicates that saponite, Mg‐Fe carbonate, and pyrrhotite are major phases and serpentine, magnetite, and pentlandite are minor phases. Anhydrous silicates are entirely absent from all micrometeorites, suggesting that their parental object has undergone heavy aqueous alteration. Saponite/serpentine ratios are higher than in the Orgueil CI chondrite and are similar to the Tagish Lake carbonaceous chondrite. Transmission electron microscope (TEM) observation indicates that serpentine occupies core regions of fine‐grained saponite, pyrrhotite has a low‐Ni concentration, and Mg‐Fe carbonate shows unique concentric ring structures and has a mean molar Mg/(Mg + Fe) ratio of 0.7. Comparison of the mineralogy to hydrated chondrites and interplanetary dust particles (IDPs) suggests that the micrometeorites are most similar to the carbonate‐poor lithology of the Tagish Lake carbonaceous chondrite and some hydrous IDPs, but they show a carbonate mineralogy dissimilar to any primitive chondritic materials. Therefore, they are a new variant of saponite‐rich micrometeorite extracted from a primitive hydrous asteroid and recently accreted to Antarctica.  相似文献   

Structure of caldera and gravity anomaly     

Izumi Yokoyama 《Bulletin of Volcanology》1963,26(1):67-72

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Seasonal Trend in the Occurrence of Nocturnal Drainage Flow on a Forested Slope Under a Tropical Monsoon Climate     

Hikaru Komatsu  Narimasa Yoshida  Hideki Takizawa  Izumi Kosaka  Chatchai Tantasirin  Masakazu Suzuki 《Boundary-Layer Meteorology》2003,106(3):573-592

Using data for one year, we examined the vertical wind speed profileson a mountain slope covered with forest in northern Thailand undera tropical monsoon climate. We defined two profile patterns: higherwind speeds at greater heights (Pattern 1) and lower wind speeds atgreater heights (Pattern 2). We classified 9.4% of the data as Pattern 2;this pattern tended to occur during the night, at low wind speeds, and with high outgoing longwave radiation. In addition, stable stratification anddecoupling between the canopy surface air and the overlying layers wereobserved when Pattern 2 occurred frequently. These facts suggested thatPattern 2 was caused by a nocturnal drainage flow. The occurrence ofPattern 2 showed a clear seasonal trend, indicating that there is a seasonaltrend in the occurrence of nocturnal drainage flows. Pattern 2 was observedmore frequently between August and February and less frequently betweenMarch and July. This corresponded to the seasonal trend in wind speed, butdid not correspond to the seasonal trend in the outgoing longwave radiation.  相似文献   

Seismic Signals Induced by Snow Avalanche Flow     

Kishimura  K.  Izumi  K. 《Natural Hazards》1997,15(1):89-100

In this paper some observations and their analysis are presented dealing with the link between seismic signals and avalanche flow. The measurements during the passage of avalanches showed a specific spindle pattern which was quite different from the one of natural earthquakes. The general trend strongly depended on the topographic features of the avalanche path, and as a result we could estimate avalanche velocity. The running power spectrum showed a meaningful shift of the dominant peak from the front to the rear part of the flow.  相似文献   

Neutron Activation Analysis of Nine GSJ Sedimentary Rock Reference Samples     

Naomi AOTA  Yutaka MIYAMOTO  Sakae KOSANDA  Yasuji OURA  Toshiyuki OKUI  Koh SAKAMOTO 《Geostandards and Geoanalytical Research》1994,18(2):185-193

Nine rock reference samples "Sedimentary rock series" issued by the Geological Survey of Japan (GSJ) were analysed for up to 31 elements by neutron activation analysis (NAA); 14MeV-NAA for Si and Al, fission track method for U, radiochemical and instrumental NAA for rare-earth elements, and instrumental NAA for the remaining elements, with reactor neutrons for the latter three. The present results are compared with reported values.  相似文献   

Characterization of the amorphous state in metamict silicates and niobates by EXAFS and XANES analyses     

Izumi Nakai  Junji Akimoto  Masayuki Imafuku  Ritsuro Miyawaki  Yoshinori Sugitani  Kichiro Koto 《Physics and Chemistry of Minerals》1987,15(2):113-124

X-ray absorption spectroscopy using synchrotron radiation has been applied to the investigation of the coordination geometries around Y, Zr and Nb atoms in metamict zircon, gadolinite, fergusonite, euxenite and samarskite. EXAFS and XANES spectra of their crystalline counterparts and synthetic compounds including ZrO₂, Y₂O₃, YNbTiO₆, YNbO₄, LiNbO₃, and NiNb₂O₆ were also measured for comparison. Metamict zircon shows a significant decrease in its Zr-O bond distances accompanying an increase in distortion of the Zr-O coordination polyhedra as compared with crystalline zircon. On the contrary, the average Nb-O bond distances and the symmetry of the coordination polyhedra around the Nb atoms in metamict euxenite and samarskite resemble those in the crystalline euxenite. Compared with crystalline fergusonite, a decrease in the distortion of the Nb-O octahedra is observed in metamict fergusonite. The structures of the second nearest neighbors (the metal-metal interactions) are largely disrupted in the metamict specimens except for metamict zircon and samarskite with high trivalent iron concentration. Nb in metamict samarskite is in octahedral coordination by oxygen and is similar to that in euxenite.  相似文献   

Characterization of Banded Iron Formations by Two-Dimensional XRF Imaging and XANES Analyses     

Masaya MATSUNAGA  Katsunori FUKUDA  Yasuhiro KATO  Izumi NAKAI 《Resource Geology》2000,50(1):75-81

Abstract: Synchrotron radiation-induced X–ray fluorescence (SR–XRF) and conventional X-ray fluorescence (XRF) analyses were applied to determine the distributions of iron, manganese, calcium, titanium, and silicon, and chemical forms of iron and trace manganese in three banded iron formation (BIF) samples. The XRF imagings on the weathered and altered BIF from the Cleaverville Formation (3. 3–3. 1 Gyr), Western Australia, showed redistributions of iron, calcium, and manganese with the disappearance of the primary bandings, while, in contrast, titanium preserved its primary depositional distribution. The XRF imagings on the BIF from the Hamersley Group (2. 5 Gyr), Western Australia, showed that manganese and titanium distribute originally at boundary region between the iron-rich mesoband and the silica-rich mesoband. The X-ray Absorption Near Edge Structure (XANES) analysis revealed that the chemical forms of manganese and iron well represent the rhythmic change of the bandings.  相似文献