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111.
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
112.
Melt water driven stream and groundwater stage fluctuations on a glacier forefield (Dammagletscher,Switzerland)
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Jan Magnusson Florian Kobierska Stephan Huxol Masaki Hayashi Tobias Jonas James W. Kirchner 《水文研究》2014,28(3):823-836
In many mountain regions, large land areas with heterogeneous soils have become ice‐free with the ongoing glacier retreat. On these recently formed proglacial fields, the melt of the remaining glaciers typically drives pronounced diurnal stream level fluctuations that propagate into the riparian zone. This behaviour was measured on the Damma glacier forefield in central Switzerland with stage recorders in the stream and groundwater monitoring wells along four transects. In spite of the large groundwater stage variations, radon measurements in the near‐stream riparian zone indicate that there is little mixing between stream water and groundwater on daily time scales. At all four transects, including both losing and gaining reaches, the groundwater level fluctuations lagged the stream stage variations and were often damped with distance from the stream. Similar behaviours have been modelled using the diffusion equation in coastal regions influenced by tidal sea level variations. We thus tested the ability of such a model to predict groundwater level fluctuations in proglacial fields. The model reproduced several key features of the observed fluctuations at three of four locations, although discrepancies also arise due to non representative input data and model simplifications. Nevertheless, calibration of the model for the individual transects yielded realistic estimates of hydraulic diffusivities between the stream and groundwater monitoring wells. We conclude that studying diurnal groundwater fluctuations can provide important information about the subsurface hydrology of alpine watersheds dominated by glacier melt. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
113.
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
114.
115.
This paper presents the first report on the occurrence of eclogite from the Kumon range of the Western province in Myanmar, which is in the southeastern extension of the Himalayan orogenic belt. The eclogite is mainly composed of omphacite, garnet, hornblende/edenite/katophorite/taramite, biotite, quartz, and rutile. The garnet grains in the eclogite usually show textures of barrier reef, atoll, and table reef types, and have a wide compositional range of Alm58–70Sps1–2Prp9–16Grs14–31. Omphacite grains that occur as garnet inclusions and as isolated crystals in the matrix have similar compositions of Jd34–45 and Jd37–44, respectively. Lesser amounts of jadeitic clinopyroxene (Jd21–38), phengite, biotite, albite, and quartz occur in the lagoon of barrier reef and atoll garnet grains. The matrix omphacite is partly replaced by symplectite of sodic clinopyroxene of Jd20–29 and albite. The lower limits of the pressure/temperature during the eclogite stage, which are defined by the assemblage of garnet, omphacite (Jd40–45), and quartz, are 1.2–1.3 GPa/530–615 °C. The finding of eclogite from Myanmar suggests the possibility of a wide occurrence of high-pressure metamorphic rocks in the ophiolite zone along the southeastern extension of the Indus-Yarlung Zangbo suture in Myanmar and Indochina. 相似文献
116.
Groundwater recharge sets a constraint on aquifer water balance in the context of water management. Historical data on groundwater and other relevant hydrological processes can be used to understand the effects of climatic variability on recharge, but such data sets are rare. The climate of the Canadian prairies is characterized by large inter-annual and inter-decadal variability in precipitation, which provides opportunities to examine the response of groundwater recharge to changes in meteorological conditions. A decadal study was conducted in a small (250 km2) prairie watershed in Alberta, Canada. Relative magnitude of annual recharge, indicated by water-level rise, was significantly correlated with a combination of growing-season precipitation and snowmelt runoff, which drives depression-focussed infiltration of meltwater. Annual precipitation was greater than vapour flux at an experimental site in some years and smaller in other years. On average precipitation minus vapour flux was 10 mm y?1, which was comparable to the magnitude of watershed-scale groundwater recharge estimated from creek baseflow. Average baseflow showed a distinct shift from a low value (4 mm y?1) in 1982–1995 to a high value (15 mm y?1) in 2003–2013, indicating the sensitivity of groundwater recharge to a decadal-scale variability of meteorological conditions. 相似文献
117.
A. Pastorello D. Sauer S. Taubenberger P. A. Mazzali K. Nomoto K. S. Kawabata S. Benetti N. Elias-Rosa A. Harutyunyan H. Navasardyan L. Zampieri T. Iijima M. T. Botticella G. Di Rico M. Del Principe M. Dolci S. Gagliardi M. Ragni G. Valentini 《Monthly notices of the Royal Astronomical Society》2006,370(4):1752-1762
Early-time optical observations of supernova (SN) 2005cs in the Whirlpool Galaxy (M51) are reported. Photometric data suggest that SN 2005cs is a moderately underluminous Type II plateau SN (SN IIP). The SN was unusually blue at early epochs ( U − B ≈−0.9 about three days after explosion) which indicates very high continuum temperatures. The spectra show relatively narrow P Cygni features, suggesting ejecta velocities lower than observed in more typical SNe IIP. The earliest spectra show weak absorption features in the blue wing of the He i 5876-Å absorption component and, less clearly, of Hβ and Hα. Based on spectral modelling, two different interpretations can be proposed: these features may either be due to high-velocity H and He i components, or (more likely) be produced by different ions (N ii , Si ii ). Analogies with the low-luminosity, 56 Ni-poor, low-velocity SNe IIP are also discussed. While a more extended spectral coverage is necessary in order to determine accurately the properties of the progenitor star, published estimates of the progenitor mass seem not to be consistent with stellar evolution models. 相似文献
118.
Based on measured stream nitrogen concentrations at outlets of 12 small sub‐areas (1·3–54·7 km2) in a largely forested catchment during the base flow period, we investigated the influences of discharges and different catchment characteristics on stream nitrogen concentration. Our field surveys were carried out during the 11‐month's period from April 2001 to February 2002 and the correlations between nitrogen concentrations and catchment characteristics were studied. The results showed that the vegetation cover was strongly correlated to total nitrogen (TN) and nitrate + nitrite ? nitrogen (NOx‐N) concentrations. That is, the TN and NOx‐N concentrations had positive correlations with mean normalized difference vegetation cover index (NDVI) of each sub‐area during dormant seasons (mean NDVI < 0 · 70) and had negative correlations during the growing season (mean NDVI ≥ 0 . 70). The significance of catchment characteristics to TN and NOx‐N concentrations was ranked as vegetation cover > soil > topography > land use, and the best models can account for 55–64% of the variance of TN and NOx‐N concentrations. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
119.
Phase relations in the system CaTiO3-CaSiO3 were experimentally examined at 5.3–14.7 GPa and 1200–1600 °C with a 6–8 type multianvil apparatus. As pressure increases, stability field of perovskite solid solution extends from CaTiO3 to CaSiO3, and the perovskite becomes stable for the entire composition range above about 12.3 GPa. The stability field of Ca(Ti1?X, SiX)2O5 (0.78<x≦1) titanite solid solution +Ca2SiO4 larnite exists in the CaSiO3-rich composition range at 9.3–12.3 GPa and 1200 °C. Perovskite solid solutions containing CaSiO3 component of 0 to 66 mol% could be quenched to 1 atm. The composition-molar volume relationship of perovskite solid solution showed that molar volume of perovskite solid solution linearly reduces from the value of CaTiO3 to that of CaSiO3. 相似文献
120.
Martin G. LOCKLEY LI Jianjun LI Rihui Masaki MATSUKAWA Jerald D. HARRIS XING Lida 《《地质学报》英文版》2013,87(1):1-20
<正>"Splitting" and "lumping" are perpetual problems in vertebrate,especially dinosaur, ichnotaxonomy.Chinese dinosaur ichnotaxonomy,which began in 1940,provides a series of interesting case studies,highlighting the dual problems of historical and dubious ichnotaxonomy. Chinese Mesozoic tetrapod track types have been placed into 63 ichnospecies(one Triassic,28 Jurassic,and 34 Cretaceous),exclusive of other,non-type ichnospecies or ichnotaxa identified from China.Fifty-two(~83%) of these 63 tetrapod ichnospecies were placed in monospecific ichnogenera. At the ichnogenus level,we prune—either by recognizing nomina dubia or by synonymy—17 from the list of 53 dinosaurian ichnogenera(a 32%reduction),leaving 36 ichnotaxa that we consider valid. Most of the cuts affect Jurassic theropod ichnotaxa,which are reduced from 23 to only nine because most ichnogenera are subjective junior synonyms of Grallator and Eubrontes.Fewer Chinese Cretaceous ichnotaxa(only six of 21 ichnogenera) are obvious nomina dubia or subjective synonyms, suggesting greater east Asian endemism during this time.Because ichnospecies differences are subtle, we provisionally retain ichnospecies as valid pending detailed comparative analyses of congeneric ichnospecies.This synthesis is long overdue and is necessary to address problems of historical and provincial ichnotaxonomy,which severely hamper comparisons of tetrapod ichnofaunas in space and time. 相似文献