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61.
Hydro-meteorological drought was assessed with respect to climate change over an estuary catchment Vu Gia-Thu Bon in Central Vietnam, which economy is dependent on agriculture. The fully-distributed hydrological model MIKE SHE was used to simulate river flow over the study region for the period 1991–2010. Drought were assessed using the Standardized Precipitation Index and the Standardized Runoff Index. The future climate was studied using the regional climate model Weather Research and Forecasting by downscaling an ensemble of three global climate models – CCSM3.0, ECHAM5 and MIROC-medium resolution over current (1961–1990) and future climates (2011–2040), under the A2 emissions scenario. The results suggest that, despite hotter and wetter future climate, the area is likely to suffer more from severe and extreme droughts, increasing about 100% in the median range for drought characteristics. Thus, there is a need for proper adaptation and planning for water resources management in this region. 相似文献
62.
通过对延长油矿延223井晚古生代孢粉组合研究以及古植被的恢复,探讨了该区晚古生代孢粉植物化石组合的地层学和古气候意义。根据孢粉化石主要属种的时代分布及其在各样品中百分含量的规律性变化,自下而上建立了3个孢粉组合:Gulisporites cochlearius-Laevigatosporites minimus组合、Sinulatisporites-Florinites组合和Lueckeisporites permianus-Platysaccus radialis组合。根据对划分孢粉组合的特征分析,通过与邻区及华北地区晚古生代孢粉组合的对比,探讨了孢粉组合的时代意义。通过孢粉组合,推测了相应时期的古植被类型,并与前人在相同地质时期所建立的大植物化石带进行了对比,分析了各地质时期植被的兴起、发展、繁盛以及衰退绝灭的历史过程,研究区二叠纪植物群属于典型的华夏植物群,反映了一种温暖潮湿的热带雨林气候,二叠纪晚期随着松柏类植物所占比例的增加,气候有变干旱的趋势。 相似文献
63.
Temporary flow patterns remain understudied, despite their wide distribution and their importance for managerial practices and river conservation. This paper explores an advanced procedure for the characterization and definition of temporary flow patterns based on the frequency, duration and magnitude of non-flow (cessation) periods. A detailed analysis of flow patterns was performed on 12 rivers of the Guadiana Basin in Southern Iberia (10 in Spain and 2 in Portugal). An open methodology that can allow managers to better characterize and improve the structure and functioning of those rivers is suggested. This methodology is based on inter- and intra-annual variability analysis and its integration with river ecotypes. Within the methodology, a set of parameters related to ecological features of temporary rivers is proposed for application. This methodology may contribute to a better definition of cessation periods and an integrated understanding of the flow requirements of temporary rivers. 相似文献
64.
In this study, a methodology for clustering 18 lakes in Alberta, Canada using the data of 19 water quality parameters for a period of 11 years (1988–2002) is presented. The methods consist of (i) principal component analysis (PCA) to determine the dominant water quality parameters, (ii) cluster analysis techniques to develop the characteristics of the clusters, and (iii) pattern‐match lakes to determine the appropriate cluster for each of the lakes. The PCA revealed that three principal components (PCs) were able to explain ～88% of the variability and the dominant water quality parameters were total dissolved solids, total phosphorus, and chlorophyll‐a. We obtained five clusters for the period 1994–1997 by using the dominant parameters with water quality deteriorating as the cluster number increased from 1 to 5. Upon matching cluster patterns with the entire dataset, it was observed that some of the lakes belonged to the same cluster all the time (e.g., cluster 1 for lakes Elkwater, Gregg, and Jarvis; cluster 3 for Sturgeon; cluster 4 for Moonshine; and cluster 5 for Saskatoon), while others changed with time. This methodology could be applied in other regions of the world to identify the most suitable source waters and prioritize their management. It could be helpful to analyze the natural controlling processes, pollution types, impact of seasonal changes and overall quality of source waters. This methodology could be used for monitoring water bodies in a cost effective and efficient way by sampling only less number of dominant parameters instead of using a large set of parameters. 相似文献
65.
66.
A biogeochemical orientation survey was carried out in the vicinity of an epithermal Au deposit in the Moisan Au–Ag mineralized area, Haenam district in Korea. The Au–Ag bearing quartz veins of the mine occur as narrow open-space fillings within Cretaceous silicic pyroclastics. The vein minerals consist mainly of quartz, sericite, pyrite, chalcopyrite, and galena, with some electrum and argentite. The main objectives of this study were to study the geochemical characteristics of rocks, soils and plants in this area, to investigate the spatial relationship between Au and associated elements in rock–soil–plant system, and to evaluate the applicability of biogeochemical prospecting for Au vein occurrences in Korea. Samples of rocks and soils, and leaves of three plant species (Japanese red pine — P. densiflora, oriental white oak — Q. aliena, Japanese mallotus — M. japonicus) were collected from the target mineralized area and control barren locations, and analyzed for trace elements by instrumental neutron activation analysis. Sampling lines were composed of one slope line which is almost parallel to the mineralized quartz-veins, and four transect lines spaced 100 m apart across the veins at 20 m sampling intervals. From the multi-element data of rock samples (n = 9), high values of Au (maximum 2030 ppb) are spatially related to Au–quartz veins. Soil samples (n = 61) collected from five sampling lines show higher values of Au (24–825 ppb) whereas soil samples from the control locations have lower values of Au (below 25 ppb). Many plant species collected from the vicinity of the veins have high Au contents compared with those at the control locations, but the ranges of Au values are variable among plant species. In a total of 128 samples of plant leaves, Q. aliena yielded Au values of 0.4 to 6.9 ppb, and M. japonicus 0.9 to 4.1 ppb. Gold contents in P. densiflora ranged from 0.1 to 5.6 ppb. Plant leaves from control areas show less than 1.6 ppb Au. The biological absorption coefficient (BAC) of Au in plants decreases in the order of Q. aliena > M. japonicus > P. densiflora. Based on the results of the study, Q. aliena appeared to be the best sampling media for biogeochemical prospecting of Au in the study area. 相似文献
67.
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69.
A New Genus and Species of Damsel-Dragonfly (Odonata: Isophlebioidea: Campterophlebiidae) in the Middle Jurassic of Inner Mongolia, China 总被引：1，自引：0，他引：1
The campterophlebiid new genus and species Ctenogampsophlebia reni is described from the Middle Jurassic of Inner Mongolia, China. It shows close similarities with the Lower to Middle Jurassic genera Gampsophlebia, and Petrophlebia, with closed and short subdiscoidal cells, confirming the attribution of these two other genera to the Campterophlebiidae. 相似文献
70.