广东省两次流体宏观异常的落实     

陈大庆  杨马陵  何璟琳  缪维成  卢帮华  黄元敏 《华南地震》2009,29(4):46-53

从外界干扰因素排除、区域构造活动异常鉴别、地下流体动力学等方面对广东省内出现的两次流体宏观异常进行了分析．讨论了引起异常的原因,从而排除了地震前兆的可能,对汶川地震后老百姓的“恐震”心理起到了安定作用。  相似文献   

Development and verification of a 3-D integrated surface water–groundwater model     

Katerina Spanoudaki  Anastasios I. Stamou  Aikaterini Nanou-Giannarou 《Journal of Hydrology》2009,375(3-4):410-427

Coupled modelling of surface and subsurface systems is a valuable tool for quantifying surface water–groundwater interactions. In the present paper, the 3-D non-steady state Navier–Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated groundwater flow equations in an Integrated suRface watEr–grouNdwater modEl (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and groundwater bodies, where water exchange takes place, using Darcy’s law. A new approach is proposed for the solution of the coupled surface water and groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water–groundwater interaction, which are chosen so that different components of the model can be tested. The model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water–groundwater interactions in real-world cases.  相似文献   

Space–time modelling of catchment scale drought characteristics     

Lena M. Tallaksen  Hege Hisdal  Henny A.J. Van Lanen   《Journal of Hydrology》2009,375(3-4):363-372

Drought may affect all components of the water cycle and covers commonly a large part of the catchment area. This paper examines drought propagation at the catchment scale using spatially aggregated drought characteristics and illustrates the importance of catchment processes in modifying the drought signal in both time and space. Analysis is conducted using monthly time series covering the period 1961–1997 for the Pang catchment, UK. The time series include observed rainfall and groundwater recharge, head and discharge simulated by physically-based soil water and groundwater models. Drought events derived separately for each unit area and variable are combined to yield catchment scale drought characteristics. The study reveals relatively large differences in the spatial and temporal characteristics of drought for the different variables. Meteorological droughts cover frequently the whole catchment; and they are more numerous and last for a short time (1–2 months). In comparison, droughts in recharge and hydraulic head cover typically a smaller area and last longer (4–5 months). Hydraulic head and groundwater discharge exhibit similar drought characteristics, which can be expected in a groundwater fed catchment. Deficit volume is considered a robust measure of the severity of a drought event over the catchment area for all variables; whereas, duration is less sensitive, particular for rainfall. Spatial variability in drought characteristics for groundwater recharge, head and discharge are primarily controlled by catchment properties. It is recommended not to use drought area separately as a measure of drought severity at the catchment scale, rather it should be used in combination with other drought characteristics like duration and deficit volume.  相似文献   

Tracing effects of decalcification on solute sources in a shallow groundwater aquifer, NW Germany     

Bettina A. Wiegand   《Journal of Hydrology》2009,378(1-2):62-71

δ⁸⁷Sr values and Ca/Sr ratios were employed to quantify solute inputs from atmospheric and lithogenic sources to a catchment in NW Germany. The aquifer consists primarily of unconsolidated Pleistocene eolian and fluviatile deposits predominated by >90% quartz sand. Accessory minerals include feldspar, glauconite, and mica, as well as disperse calcium carbonate in deeper levels. Decalcification of near-surface sediment induces groundwater pH values up to 4.4 that lead to enhanced silicate weathering. Consequently, low mineralized Ca–Na–Cl- and Ca–Cl-groundwater types are common in shallow depths, while in deeper located calcareous sediment Ca–HCO₃-type groundwater prevails. δ⁸⁷Sr values and Ca/Sr ratios of the dissolved pool range from 7.3 to −2.6 and 88 to 493, respectively. Positive δ⁸⁷Sr values and low Ca/Sr ratios indicate enhanced feldspar dissolution in shallow depths of less than 20 m below soil surface (BSS), while equilibrium with calcite governs negative δ⁸⁷Sr values and elevated Ca/Sr ratios in deep groundwater (>30 m BSS). Both positive and negative δ⁸⁷Sr values are evolved in intermediate depths (20–30 m BSS). For groundwater that is undersaturated with respect to calcite, atmospheric supplies range from 4% to 20%, while feldspar-weathering accounts for 8–26% and calcium carbonate for 62–90% of dissolved Sr²⁺. In contrast, more than 95% of Sr²⁺ is derived by calcium carbonate and less than 5% by feldspar dissolution in Ca–HCO₃-type groundwater. The surprisingly high content of carbonate-derived Sr²⁺ in groundwater of the decalcified portion of the aquifer may account for considerable contributions from Ca-containing fertilizers. Complementary tritium analyses show that equilibrium with calcite is restricted to old groundwater sources.  相似文献   

Shared microsporidian profiles between an obligate (Niphargus) and facultative subterranean amphipod population (Gammarus) at sympatry provide indications for underground transmission pathways     

《Limnologica》2016

Only sparse knowledge exists on amphipod-infecting microsporidians in subterranean waters. Here, we DNA barcoded two sympatric amphipod populations (obligate subterranean Niphargus schellenbergi, facultative Gammarus fossarum) and their microsporidian parasites. Parasite prevalence was assessed by diagnostic PCR assays. Overall prevalence was 82.7 %. Both amphipod populations shared all four identified parasite species (Nosema granulosis, Microsporidium sp. I, Orthosomella sp., Microsporidium sp. BPAR3). Hence, we postulate underground transmission pathways of microsporidians mediated by subterranean amphipod hosts.  相似文献   

2012年10月后皖27井水位下降成因分析^*     

方震  孙盼盼  李军辉  李玲利  汪丹丹  王远 《地震》2016,36(2):85-93

地下水动态的异常变化既有可能是地震前兆异常信息,也有可能是某种环境干扰所引起的,如何及时识别并排除环境干扰,对于成功判定地震前兆异常至关重要。马鞍山皖27井水位自2012年10月以来反复出现下降型异常,下降程度超正常年份最低值,最大降幅达70cm。为了准确客观地判定该异常的成因,本文利用水化学和物理相结合的方法对皖27井地下水动态变化成因及开采干扰进行分析,研究表明:大气降水在皖27井水补给源中占了一定的份额,除此之外,还存在深部补给来源;深井抽水活动影响着皖27井水位的变化,但不能将皖27井本次异常变化完全归因于深井抽水,区域构造活动是引起本次水位异常的主要原因。本文所采取的异常识别与分析方法,为今后地下水动态异常识别及前兆判定工作提供重要依据。  相似文献   

Groundwater transport modeling with nonlinear sorption and intraparticle diffusion     

《Advances in water resources》2014

Despite recent advances in the mechanistic understanding of sorption in groundwater systems, most contaminant transport models provide limited support for nonideal sorption processes such as nonlinear isotherms and/or diffusion-limited sorption. However, recent developments in the conceptualization of “dual mode” sorption for hydrophobic organic contaminants have provided more realistic and mechanistically sound alternatives to the commonly used Langmuir and Freundlich models. To support the inclusion of both nonlinear and diffusion-limited sorption processes in groundwater transport models, this paper presents two numerical algorithms based on the split operator approach. For the nonlinear equilibrium scenario, the commonly used two-step split operator algorithm has been modified to provide a more robust treatment of complex multi-parameter isotherms such as the Polanyi-partitioning model. For diffusion-limited sorption, a flexible three step split-operator procedure is presented to simulate intraparticle diffusion in multiple spherical particles with different sizes and nonlinear isotherms. Numerical experiments confirmed the accuracy of both algorithms for several candidate isotherms. However, the primary advantages of the algorithms are: (1) flexibility to accommodate any isotherm equation including “dual mode” and similar expressions, and (2) ease of adapting existing grid-based transport models of any dimensionality to include nonlinear sorption and/or intraparticle diffusion. Comparisons are developed for one-dimensional transport scenarios with different isotherms and particle configurations. Illustrative results highlight (1) the potential influence of isotherm model selection on solute transport predictions, and (2) the combined effects of intraparticle diffusion and nonlinear sorption on the plume transport and flushing for both single-particle and multi-particle scenarios.  相似文献   

Impact of fracture network geometry on free convective flow patterns     

《Advances in water resources》2014

The effect of fracture network geometry on free convection in fractured rock is studied using numerical simulations. We examine the structural properties of fracture networks that control the onset and strength of free convection and the patterns of density-dependent flow. Applicability of the equivalent porous medium approach (EPM) is also tested, and recommendations are given, for which situations the EPM approach is valid. To date, the structural properties of fracture networks that determine free convective flow are examined only in few, predominantly simplified regular fracture networks. We consider fracture networks containing continuous, discontinuous, orthogonal and/or inclined discrete fractures embedded in a low-permeability rock matrix. The results indicate that bulk permeability is not adequate to infer the occurrence and magnitude of free convection in fractured rock. Fracture networks can inhibit or promote convection depending on the fracture network geometry. Continuous fracture circuits are the crucial geometrical feature of fracture networks, because large continuous fracture circuits with a large vertical extent promote convection. The likelihood of continuous fracture circuits and thus of free convection increases with increasing fracture density and fracture length, but individual fracture locations may result in great deviances in strength of convection between statistically equivalent fracture networks such that prediction remains subject to large uncertainty.  相似文献   

Monitoring land subsidence and fault deformation using the small baseline subset InSAR technique: A case study in the Datong Basin,China     

《Journal of Geodynamics》2014

The Datong Basin is located to the north of the Fenwei Graben Basin, where ground fissures and subsidence are common geological hazards. The Datong Basin is also one of China's main energy bases and is known as “the hometown of coal”. In this study, the small baseline subset InSAR technique was used to process 40 scenes of Envisat ASAR images that cover this area. The magnitude and distribution of subsidence in the Datong Basin were obtained. Additionally, the relationships among the regional land subsidence, ground fissures and fault activity were addressed. The results reveal that Datong ground subsidence is affected by the groundwater exploitation and the nearby faults. The Datong ground fissures are controlled by regional fault activity (e.g., seismic activity) and its interaction with the ground subsidence. Meanwhile, the influence of surface precipitation on ground fissure activity was analyzed. The differential subsidence on both sides of the ground fissures was also studied.  相似文献   

经验模态分解法在安徽省南部地下流体分析中的应用     

孙盼盼  张军  方震  陶月潮  王俊 《高原地震》2014,26(3):33-37

首次引进经验模态分解法（EMD）对安徽省南部地下流体进行分析。通过对地下流体数据的分解与重构,发现该方法能提取不同尺度的水位动态,效果较好。通过对震例的总结发现：显著地震前、后安徽省南部地下流体EMD重构结果均出现异常,且存在某些地震前兆敏感点。同时,还对地震前地下流体的变化原因进行了初步分析。  相似文献