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91.
推求城市暴雨强度公式参数中准则函数的选择问题 总被引:1,自引:0,他引:1
詹士昌 《应用基础与工程科学学报》2006,14(2):194-202
针对城市暴雨强度公式制定中准则函数的选择问题,以绝对标准差最小准则、相对标准差最小准则,以及加权耦合的绝对与相对标准差最小准则等为推求暴雨强度公式最优参数的优化准则,采用性能较为优异的蚁群算法进行优化估计,并用实际资料对城市暴雨强度公式的不同准则和不同拟合方法的推求结果进行比较、检验和分析,系统研究了推求城市暴雨强度公式参数中准则函数的选择问题,为各地城市暴雨强度公式的制定提供了精确、科学、可行的依据. 相似文献
92.
同位素水文学研究综述 总被引:2,自引:4,他引:2
综述了国内外同位素水文学研究的主要成果,认为同位素示踪方法在解决某些水文、水资源及环境地质问题方面优势比较明显,并且有助于从宏观和微观上阐明水循环过程中各相关要素的变化情况,揭示某些水文基本现象的内在规律;指出了同位素水文学研究当前存在的问题和今后的一些重点课题,并对同位素技术或方法在水文学中的应用前景进行了展望. 相似文献
93.
Daniel Okubay Tewolde Paul Koeniger Matthias Beyer Christoph Neukum Maike Gröschke Melanie Ronelngar 《Isotopes in environmental and health studies》2013,49(5):459-477
ABSTRACTThe Lake Chad Basin (LCB) is an endorheic transboundary catchment highly vulnerable to drought. For effective groundwater management, recharge areas need identification and replenishment quantification. At present, little research exploring unsaturated zone water flow processes and groundwater recharge are available. In this study, 12 vertical soil profiles were analysed for stable water isotopes and chloride concentration to estimate evaporation and groundwater renewal. Most δ18O and δ2H isotope profiles reveal typical arid environment patterns, with maximum enrichment at depths between 2.5 and 20?cm and depletion towards the surface (atmospheric influence) and depth (mixing and diffusion). Average annual dry season evaporation rates in Salamat and Waza Logone range from 5 to 30?mm, in Bahr el Ghazal and Northern Lake Chad from 14 to 23?mm. According to the chloride mass balance (CMB), the average annual recharge rate is estimated between 3 and 163?mm in Salamat and Waza Logone and less than 1 mm in Bahr el Ghazal and Northern Lake Chad. Based on the CMB results, potential recharge sites were identified, while estimated soil evaporation corresponds to plant water use at the initial growing stage, which is an important component in irrigation water management. 相似文献
94.
R. Trettin G. Haase M. Habedank J. Tesch 《Isotopes in environmental and health studies》2013,49(12):595-598
From a sector within an extended Tertiary basin 21 groundwater samples as well as 3 rock samples of a Zechslein diapir were analysed for 87Sr/86Sr-ralio. As a tendency the isotope ratio of the dissolved strontium is decreasing with increasing depth and strontium content. Furthermore, strontium content and salinity are correlated. With two exceptions the isotope data are in the range between about 0.7080 and 0.7100. Significant differences in the strontium isotope composition were found between the Zechstein salts and the typical groundwaters. This shows, that the Zechstein diapir can not be the source of the higher salinity in parts of the groundwater system. The results are discussed. 相似文献
95.
Abstract Recharge areas in hard rocks of the margin of the Mygdonias-Basin (Greece) with the origin of thermal waters (max. 50°C) are assumed. Environmental isotopes, 3H, D, 18O. 13C, 34S are supporting a concept of recharging normal temperated water along the northern margin of the basin, especially in the cross-area of tectonic faults. 相似文献
96.
Pooja Devi Ashok Kumar Jain M. Someshwer Rao Bhishm Kumar 《Isotopes in environmental and health studies》2013,49(3):426-438
A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability. 相似文献
97.
Abstract During hydraulic dumping of ashes at a sludge bed of the power plant at Mělnik (north of Prague), new springs originated which wetted houses and properties at the small village of Podvlci. The sludge bed as well as the village lie at the southwestern margin of the alluvial plain of the Labe (Elbe) River at the foot of a slope built of Cretaceous sedimentary rocks. By analyzing the concentrations of radiocarbon and tritium, it was possible to determine the origin of the water and the ratio of the modern and original groundwater in the new springs in the surroundings of the sludge bed. To substitute the present dump the operation of which should be stopped, establishing of a new one has been proposed within the alluvial plain. By means of stable isotopes and radionuclides, the relations between the groundwater in the Quaternary sediments and in the underlying Middle Turonian confined aquifer were studied, because changes in the hydrogeological regime have to be expected due to the operation of the proposed new sludge bed. 相似文献
98.
E.A.N.V. Edirisinghe H.A. Dharmagunawardhane R.L. Wijayawardane 《Isotopes in environmental and health studies》2017,53(6):628-645
Seasonal and spatial variation in δ18O and δ2H in rainwater was determined in three selected transects across Sri Lanka, the tropical island in the Indian Ocean. Local meteoric water lines (LMWLs) for three distinguished climatic zones; wet, dry and intermediate were constructed. LMWLs show slight variations in their gradients and respective d-excess values, depending on the air moisture origin, circulation and environmental conditions of each climatic zone. The elevation effect and amount effect could be identified but the continental effect is not significantly seen in the isotope composition of rain in the concerned areas. The results reasonably revealed that the distinct rainfall regimes; two monsoonal rains and two convectional (inter-monsoon) rains have characteristic isotopic signatures. Also the impact of (i) terrestrial and oceanic moisture sources, (ii) depression and cyclonic conditions of the Bay of Bengal, and (iii) topography of the country on the variation of the isotopic composition of rain in Sri Lanka could be satisfactorily identified. 相似文献
99.
Haiping Qi Tyler B. Coplen Lauren Tarbox Jennifer M. Lorenz Martha Scholl 《Isotopes in environmental and health studies》2014,50(4):442-447
A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ2H) and stable oxygen (δ18O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ2H and δ18O values of this reference water are?2.0±0.4 and?2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ2H and δ18O values of Standard Light Antarctic Precipitation reference water are?428 and?55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (U=2uc) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule. 相似文献
100.