A new package for simulating periodic boundary conditions in MODFLOW and SEAWAT

Modeling of coastal groundwater systems is a challenging problem due to their highly dynamic boundary conditions and the coupling between the equations for groundwater flow and solute transport. A growing number of publications on aquifers subject to tides have demonstrated various modeling approaches, ranging from analytical solutions to comprehensive numerical models. The United States Geological Survey code SEAWAT has been a popular choice in studies of this type. Although SEAWAT allows the incorporation of time-variant boundary conditions, the implementation of tidal boundaries is not straightforward, especially when a seepage face develops during falling tide. Here, a new package is presented, called the periodic boundary condition (PBC) package, that can be incorporated into MODFLOW and SEAWAT to overcome the difficulties encountered with tidal boundaries. It dynamically updates the boundary conditions for head and concentration during the simulation depending on a user-defined tidal signal and allows for the development of a seepage face. The package has been verified by comparing it to four different published models of tidally influenced groundwater systems of varying complexity. Excellent agreement was obtained in all cases. The new package is an important extension to the existing capabilities of MODFLOW and SEAWAT with respect to simulating periodic boundary conditions.     

模糊综合评判在矿井水文地质类型划分中的应用

以羊东矿为例,通过分析羊东矿水文地质条件,依据《煤矿防治水规定》对矿井水文地质类型进行评定分类.结合使用模糊综合评判,对羊东矿水文地质类型进行重新划分,与原分类结果一致,进一步证明模糊综合评判法在矿井水文地质类型划分中应用的可行性.为煤矿水文地质分类方面提供了科学依据、注入了新的思想.     

地下水化学动力学方法运用中若干问题的探讨

文中对用地下水化学动力学方法计算出的五种水文地质参数(渗透系数K、导水系数T、渗透速度K实际速度“、贮留时间t)定量评价研究区水文地质条件的整个过程中存在的问题进行了较全面的分析，也就是对用地下水动力学公式求出K值或者T值之后，再由K值或者T值反算推出的地下水化学动力学常数K或者K’j的整个过程中可能引起的误差因素进行了逐个分析并加以说明。对这五种水文地质参数获取的整个过程中能够引起计算结果出现误差的各种因素进行了较全面分析。     

“Landscape Prompts” Awaiting Attendance: Uncovering the Persistent Factors That Shape the Drowned Lands

The Black Dirt Region in the State of New York has been well-known for the unique taste of its onions, which is attributed to the organic matter that weighs over 80% in the soil. In recent years, however, the rigid economic pattern restrains the development of this area. In the meantime, local agricultural production is more and more vulnerable to flooding. When this region is labeled as “highly productive of crops,” the persistent factors that have been shaping the black-dirt landscape are omitted. The other name of the place, “the Drowned Lands,” may better capture its entangled relationship with water. In this article, hydrogeological dynamics and human desire are regarded as the factors that sustain landscape continuity and stability. Based on the research on historical sedimentation in the Drowned Lands, this article attempts to delineate a local scenario of covert landscape evolution since the Last Glacial Maximum. The proposal initiates a composite pathway of ecological functions and touristic values in the agricultural region. Within a series of “landscape prompts,” a lesser-known tale of local geology and prehistoric culture is told. Through design interventions, alternative possibilities of rural landscape are tested, embedded meaning of the agricultural land becomes tangible, and a more adaptive human–land relationship is restored.     

WTFM, software for well test analysis in fractured media combining fractional flow with double porosity and leakance approaches

The identification of the hydraulic characteristics and transport properties of fractured reservoirs requires the development of specific models that account for (i) the medium heterogeneity, e.g. the presence of major conductive fractures that delimit capacitive matrix blocks, with weakly open, dead end or isolated fractures, and (ii) for the geometrical arrangement of the major conductive fractures network, which dominates the flow at the scale of the well tests.Well Tests in Fractured Media (WTFM) software takes into account these two main features by combining radial flow generalized to fractional dimension, with the theory of double-porosity, including diffusivity in the second porosity, transient inter-porosity flow and inter-porosity skin effect, and with leakance. The implementation of this nD model, with n fractional, extends usefully the domain of application of the usual 1D/2D/3D double-porosity/leakance models for a large range of connection levels of fracture networks. Although the fractures geometry and properties are not considered one by one, or by directional families, they are taken into account by averaged properties and by the impact that the whole network has on the hydrodynamic behaviour. The accuracy of the coupled transient behaviours analysis is augmented by taking into account wellbore storage and skin effects. All together, the use of these different options allows matching a wide range of pumping test curves, characteristics of distinctive behaviours, with a limited number of parameters. Distinctive well test experiments, in both sedimentary and crystalline rocks, are presented for enlightening how the pertinent use of the model options improves predictions.     

Groundwater management strategies,Rohtas District,Bihar, India

The district of Rohtas in north east India has severe problems in obtaining adequate water supplies for its numerous villages and hamlets. The area has a very low and unreliable rainfall. The problems are compounded in areas where the bedrock is hard and hence difficult to drill such that wells have been started but not completed to the necessary depths. Some recommendations are made to assist the acquisition of a more dependable water supply.     

同位素分析法在三山岛金矿的应用

三山岛矿区地下水质有海水、第四系水、基裂岩隙水、地下热水、淡水等。为了适应矿区生产的需要,需对水质进行分析。但是,常规的水质简分析法只能鉴别水的类型,不能提供其它资料,为此采用同位素分析法。该法不仅能验证水文地质研究提供的结果,还能提供水文地质研究不易取得的数据与资料,如地下水相对停留时间,不同成因不同成分的地下水补给源的补给量及其比例。     

Numerical modeling of the effects of roughness on flow and eddy formation in fractures

The effect of roughness on flow in fractures was investigated using lattice Boltzmann method (LBM). Simulations were conducted for both statistically generated hypothetical fractures and a natural dolomite fracture. The effect of increasing roughness on effective hydraulic aperture, Izbash and Forchheimer parameters with increasing Reynolds number (Re) ranging from 0.01 to 500 was examined. The growth of complex flow features, such as eddies arising near the fracture surface, was directly associated with changes in surface roughness. Rapid eddy growth above Re values of 1, followed by less rapid growth at higher Re values, suggested a three-zone nonlinear model for flow in rough fractures. This three-zone model, relating effective hydraulic conductivity to Re, was also found to be appropriate for the simulation of water flow in the natural dolomite fracture. Increasing fracture roughness led to greater eddy volumes and lower effective hydraulic conductivities for the same Re values.     

Hydrogeological and geochemical studies of the Efteni and Derdin geothermal areas,Turkey

The Efteni and Derdin geothermal areas are located in northwestern Turkey. Relatively low-temperature springs emerge from the Duzce Fault, a normal-component-dominated fault segment of the North Anatolian Fault System. The thermal waters of the Efteni and Derdin Springs show distinct geochemical and isotopic characteristics since they originate from different geothermal reservoirs and reflect the effects of different water–rock interaction processes. Geothermometry revealed higher reservoir temperatures for the Efteni system, however a strong δ¹⁸O shift, interpreted as being the result of isotopic exchange at high temperatures, was observed in the Derdin system. Hydrogeological and geochemical techniques are applied to identify recharge mechanisms, water–rock interaction processes and to construct conceptual models of these geothermal systems.     

Building a geodatabase for mapping hydrogeological features and 3D modeling of groundwater systems: Application to the Saguenay-Lac-St.-Jean region, Canada

Understanding and managing groundwater resources require the integration of a large amount of high-quality data from a variety of sources. Due to the limitations in accessing information related to groundwater and subsurface conditions, the gathering of available existing information is of crucial importance when conducting a successful hydrogeological study. Here, we present an approach for the development of an exhaustive and comprehensive groundwater database through (1) the gathering of relevant sources of information relating to groundwater, and (2) the application of a quality control process in order to screen the data for accuracy and quality. This hydrogeological database is then implemented within a GIS (geographic information system) framework coupled to a Relational Database Management System (RDBMS) as a personal geodatabase (ESRI format) GIS technology. Once established, the spatial database allows a user to request the relevant data required for a specific hydrogeological study. In addition, stratigraphic data stored within the spatial database may be utilized for constructing 3D subsurface hydrostructural models. In order to achieve this objective, the software Arc Hydro Groundwater combined with the ArcGIS spatial database is shown to be appropriate for the 3D structural representation of aquifers (groundwater reservoirs). The innovative contribution of this approach in building 3D hydrostructural subsurface models from a spatial database resides in simplifying the required step-by-step processes by considering a unified compatible combination of “RDBMS-ArcGIS-Arc Hydro Groundwater” technologies. The proposed methodology is illustrated using data from an ongoing project aimed at developing an inventory of the groundwater resources of the Saguenay-Lac-Saint-Jean region, Quebec (Canada).