Application of grey numerical model to groundwater resource evaluation

Based on interval grey number theory, a grey numerical model was developed to simulate groundwater flow in two-dimensional porous-medium aquifer. The solution method proposed in this paper ensures the integrity and validity of the grey data transportation in the calculation processes. Because most of the parameters characterizing groundwater flow are of grey nature, a grey model can better describe the groundwater flow than the traditional white model. The method was applied to evaluate the sustainable groundwater resource in a groundwater basin of north China. The results from the case study help develop the most appropriate approaches to utilize the water resources in the area.     

地下水资源管理预警系统的建立及应用研究 --以长春城区为例

由于长春城区地下水的超采产生了环境恶化,结合地下水预测模型和地质及水文地质条件,以长春城区为例建立了地下水资源管理预警模型。根据长春城区的地质及水文地质条件提出水位水质预警标准,并根据模型编制了地下水资源管理预警系统。利用所建立的预警系统,对现状和未来开采条件下水位水质进行预警,从而为水资源的科学管理和持续利用提供可靠依据和保障。     

冲洪积扇含水层地下水可开采量数值模拟——以文峪河冲洪积扇为例

依据钻孔岩性,水文地质资料,将文峪河冲洪积扇平原分为上游单一潜水区和中下游承压水区,中下游垂向划分为上部弱水含水层和下部较强承压水含水层,对上游潜水和中下游承压水用二维侧向流数学模型,对中下游弱潜水用一维垂向流数学模型,在计算了现状开采条件下的水资源基础上,进一步计算出,在扇上游集中采水时,按工业开采和农业开采,以地下水多年总补排均衡,水位长期稳定的约束条件地下水可开采量。     

城市地下水可采资源与管理模型研究中的几个问题：以河南漯河市为例

文章以漯河市为例说明了城市地下水最大可采资源的确定和开发管理中遵循不断变化着的实际情况,走科研与生产相结合道路的必要性。全文分3个方面介绍了开采条件下的人工串层补给,随机边界条件及地下水管理模拟中常见的几个核心问题的处理。文章最后强调,地下水数值模拟中辅以同位素年龄研究的重要性。     

城市地下水赋存环境分析与数值模拟——以长春城区为例

以长春城区为例,分析了城市地下水赋存环境的演变,概化出该区的水文地质概念模型。将土地利用类型和供水管道渗漏对地下水补给的影响纳入城市地下水数值模拟中,经过模型识别,实测水位与计算水位的绝对误差<0.5 m,井点数占观测井总数的85%,经检验满足国家标准(GB/T14497-93)要求。结果表明,模型细化后,水位拟合精度有所提高。     

Development of a numerical groundwater flow model using SRTM elevations

Remotely-sensed elevation data are potentially useful for constructing regional scale groundwater models, particularly in regions where ground-based data are poor or sparse. Surface-water elevations measured by the Shuttle Radar Topography Mission (SRTM) were used to develop a regional-groundwater flow model by assuming that frozen surface waters reflect local hydraulic head (or groundwater potential). Drainage lakes (fed primarily by surface water) are designated as boundary conditions and seepage lakes and isolated wetlands (fed primarily by groundwater) are used as observation points to calibrate a numerical flow model of the 900 km² study area in the Northern Highland Lakes Region of Wisconsin, USA. Elevation data were utilized in a geographic information system (GIS) based groundwater-modeling package that employs the analytic element method (AEM). Calibration statistics indicate that lakes and wetlands had similar influence on the parameter estimation, suggesting that wetlands might be used as observations where open water elevations are unreliable or not available. Open water elevations are often difficult to resolve in radar interferometry because unfrozen water does not return off-nadir radar signals.     

Use and abuse of the urban groundwater resource: Implications for a new management strategy

Various human activities threaten the groundwater quality and resource under urban areas, and yet residents increasingly depend on it for their livelihood. The anticipated expansion of the worlds urban population from 3 to 6 billion in the coming 50 years does not only pose a large water management threat but also provides an opportunity to conserve groundwater in a better way than up to now. The authors argue for a new way to manage urban activities in order to conserve the precious groundwater resource. The focus is on the quality of the discharged water after use in households. Restrictions on what is added to water while using it, e.g. detergents, excreta, paint residues, oils, and pharmaceuticals, are important to simplify the treatment and reuse of used water. Avoiding mixing different wastewater flows has the same positive effect. If increased volumes of wastewater can be treated and reused, the demand on the groundwater resource is reduced, as also occurs with demand management measures. Reduced discharge of polluted water to the environment from households and utilities also conserves the quality of groundwater and reduces sophisticated treatment costs.

---

Resumen La urbanización lleva a una demanda elevada y concentrada de agua de calidad adecuada, acompañada por el vertido de volúmenes análogamente mayores de aguas residuales. Los alimentos se importan a ciudades donde los microorganismos y nutrientes de los excrementos humanos son descargados a ríos, lagos y, también, aguas subterráneas. Más aún, gran número de los bienes de consumo son eliminados vía las tuberías de las cloacas. Las deudas medioambientales, es decir, el empobrecimiento de las condiciones medioambientales, que requerirán de aportaciones humanas y económicas para rehabilitarlas, son comunes a todas las ciudades, sobretodo en el Hemisferio Sur, donde, según la Valoración Global de Suministro de Agua y Saneamiento (OMS y UNICEF), la mayor parte de las aguas residuales urbanas no son tratadas (65% en Asia, 86% en Latinoamérica, 100% en África). La tarea pendiente consiste en proteger los recursos de aguas subterráneas para que estén disponibles de forma rápida para los habitantes urbanos también el futuro. En los próximos 50 años, se espera que la población urbana aumente de 3,000 a 6,000 millones de personas, según estimaciones de las Naciones Unidas, por lo que es imperativo dejar de contaminar las aguas subterráneas existentes bajo las nuevas áreas urbanas en construcción. En este artículo, se escudriña la calidad de las aguas subterráneas y su protección a la luz de los cambios recientemente introducidos en las políticas del agua, esto es, desde la gestión de los abastecimientos de agua a la gestión de la demanda y, eventualmente, hastaa la gestión de la reutilitzación.

---

Résumé Lurbanisation conduit à une demande élevée et concentrée deau de qualité adéquate, accompagnée du rejet dimportants volumes correspondants deaux usées. La nourriture est importée dans les villes tandis que les micro-organismes et les nutriments provenant des excrétas humains sont rejetés dans les rivières, les lacs et aussi les eaux souterraines. De plus, une large gamme de biens de consommation est évacuée par les égouts. Les créances environnementales, cest-à-dire lappauvrissement des conditions environnementales qui demandera des apports humains et économiques pour la réhabilitation, sont habituelles dans toutes les villes, et pas seulement dans lhémisphère sud, comme cela est indiqué dans le rapport sur lalimentation en eau et la santé publique du monde (publié par lOMS et UNICEF), établissant que la plupart des eaux résiduaires des zones urbaines reste non traitée (65% en Asie, 86% en Amérique latine et 100% en Afrique). La tâche à réaliser pour lhomme est de protéger les ressources en eau souterraine en sorte quelle reste disponible pour les habitants des villes dans le futur. Dans les prochaines 50 années, il faut sattendre à ce que la population urbaine saccroisse de 3 à 6 milliards de personnes selon les estimations des Nations Unies; aussi il est impératif de ne pas continuer à polluer les eaux souterraines sous les nouvelles zones urbaines en cours de construction. Dans cet article, nous analyserons la qualité des eaux souterraines et leur protection à la lumière des récents changements de politique de leau, cest-à-dire de la gestion de lalimentation en eau jusquà une gestion de la demande et en abordant éventuellement la période de gestion du recyclage.

     

Changes in groundwater chemistry due to metallurgical activities in an alluvial aquifer in the Moa area (Cuba)

The aim of this work is to evaluate the changes in groundwater chemistry in an alluvial aquifer in the Moa area. Surface and ground water, metallurgical waste and various geological material samples were collected in order to evaluate groundwater composition. The results show that the alluvial aquifer is polluted with SO₄^2-, Mg²⁺and heavy metals. According to its major components in the alluvial aquifer, two types of groundwater are identified: magnesi-bicarbonated and sulphate-magnesic. Maximum SO₄^2– and Mg²⁺ contents are more than 1000 mg/L, and are four times higher than the acceptable levels for human consumption of water. The high values of Cr(VI), Ni(II), Mn(II) Fe_(total), SO₄^2– and Mg²⁺ in alluvial aquifers are due to polluted recharge from metallurgical waste from the tailing dam. This recharge is favoured by the preferential flow due to desiccation cracks in metallurgical waste. Geochemical modelling showed that potentially toxic heavy metals might exist largely in the forms of MSO₄^2– and M²⁺ in pore water of SAL metallurgical waste. All samples were supersaturated in goethite and hematite. Results from batch testing indicate that the heavy metals have two origins: natural, due to the existing ultramaphic rocks and laterites, and anthropogenic, by metallurgical waste rich in sulphate and (oxy)hydroxide minerals. These results highlight the need to locate and evaluate a new water source to supply the population of the city of Moa.     

北京市平谷盆地地下水三维数值模拟及管理应用

为缓解北京城区的用水紧张问题,平谷区建立了王都庄和中桥两个应急水源地。持续过量的开采导致盆地内水位急剧下降。为研究大规模开采对平谷盆地地下水系统的影响,并分析不同地区的开采潜力,本文建立了合理刻画三维地下水流动特征的数值模型,对五种不同的开采方案进行模拟。模拟结果表明,丰水条件下地下水位回升明显,王都庄水源地补给条件优越,尤其是盆地上游地区,具有更大的开采潜力;而盆地中下部应适当限制开采,避免水位下降过快。高仿真的数值模型可作为强有力的管理辅助工具,为地下水资源分析及合理利用提供科学的技术支持。     

Development of a numerical model for nitrates in groundwater in the reservoir area of the Komesu subsurface dam, Okinawa, Japan

A numerical model consisting of simplified equations was developed to simulate nitrate concentrations in groundwater in a reservoir area of a subsurface dam in a Quaternary limestone region. The model was composed of a water balance sub-model and a nitrogen balance sub-model; the water balance sub-model was built from tank models which can express the quick dilution near caves and the effect of dam construction; and the nitrogen balance sub-model was made to represent changes in nitrogen forms and movement of nitrogen in the soil and aquifer zones. The model was calibrated and verified by observed data before and after the dam construction and then applied to a predictive simulation under a simple assumption that rainfall descends gradually. The model seemed applicable to long-term prediction of changes in NO₃-N in the reservoir area.     

鸡西市城区地下水资源评价

鉴于鸡西市城区地下水资源类型、赋存条件、补排关系,量与质的现状,结合前人有关资料进行分析评价,提高人们对地下水资源的认识,提倡合理开采,取储兼顾、开源节流,管好用好地下水资源,更好地为城区经济建设服务。     

Modelling the vulnerability of groundwater to contamination in an unconfined alluvial aquifer in Pakistan

The area of Thal Doab is located in the Indus Basin and is underlain by a thick alluvial aquifer called the Thal Doab aquifer (TDA). The TDA is undergone intense hydrological stress owing to rapid population growth and excessive groundwater use for livestock and irrigated agricultural land uses. The potential impact of these land uses on groundwater quality was assessed using a DRASTIC model in a Geographic Information System environment. Seven DRASTIC thematic maps were developed at fixed scale and then combined into a groundwater vulnerability map. The resultant vulnerability index values were grouped into four zones as low, moderate, high and very high. The study has established that 76% of the land area that is underlain by the TDA has a high to very high vulnerability to groundwater contamination mainly because of a thin soil profile, a shallow water table and the presence of soils and sediments with high hydraulic conductivity values. In addition, only 2 and 22% of the total area lie in low and moderate vulnerability zones, respectively. The outcomes of this study can be used to improve the sustainability of the groundwater resource through proper land-use management.     

Investigating groundwater flow components in an Alpine relict rock glacier (Austria) using a numerical model

Relict rock glaciers are complex hydrogeological systems that might act as relevant groundwater storages; therefore, the discharge behavior of these alpine landforms needs to be better understood. Hydrogeological and geophysical investigations at a relict rock glacier in the Niedere Tauern Range (Austria) reveal a slow and fast flow component that appear to be related to the heterogeneous structure of the aquifer. A numerical groundwater flow model was used to indicate the influence of important internal structures such as layering, preferential flow paths and aquifer-base topography. Discharge dynamics can be reproduced reasonably by both introducing layers of strongly different hydraulic conductivities or by a network of highly conductive channels within a low-conductivity zone. Moreover, the topography of the aquifer base influences the discharge dynamics, which can be observed particularly in simply structured aquifers. Hydraulic conductivity differences of three orders of magnitude are required to account for the observed discharge behavior: a highly conductive layer and/or channel network controlling the fast and flashy spring responses to recharge events, as opposed to less conductive sediment accumulations sustaining the long-term base flow. The results show that the hydraulic behavior of this relict rock glacier and likely that of others can be adequately represented by two aquifer components. However, the attempt to characterize the two components by inverse modeling results in ambiguity of internal structures when solely discharge data are available.     

Great tritium ages explain the occurrence of good-quality groundwater in a phreatic aquifer of an urban area, Lublin, Poland

The phreatic aquifer of the Lublin chalk in the watershed of the Bystrzyca River, eastern Poland, is characterized by waters of good quality. Its hydraulic conductivity is related to a fissure network of low porosity, as much as 0.006 at the outcrops. The good quality of water in this urban setting is surprising because, according to estimates based on Darcy's law, a high seepage velocity would be expected, resulting in rapid transport of pollutants in the aquifer. However, tritium sampling reveals that the mean ages range from about 55 to 92 years in four cases, and about 250 to 350 years in 11 cases. One sampling site is free of tritium, which indicates an even greater age. Such great ages can be explained only by a retardation of solute transport due to matrix diffusion, that is, an exchange between mobile water in the fissures of low porosity and stagnant water in the matrix of high porosity. The delay factor is given as the ratio of total porosity to fissure porosity. In consequence, all types of dissolved constituents and, to some degree, fine suspended matter are delayed in their transport to springs and wells. In addition, non-conservative constituents have longer times to sorb, react, and decay than in the case of transport without a dominant influence of matrix diffusion. Though pollutants are greatly delayed, their accumulation in the matrix and slow diffusion into the fissures contribute to their persistence in groundwater. Regional values of hydraulic conductivity, estimated from tritium ages and known matrix porosity, agree reasonably well with the values known from pumping tests, which supports the interpretation of a dominant influence of matrix diffusion on solute transport. Electronic Publication     

Assessment of water seepage through a geologic barrier surrounding a large reservoir using groundwater levels, soil condition, and a numerical model

Though the geologic barrier surrounding a dam reservoir plays an important role in preventing water seepage to the outside of a reservoir, a detailed survey to assess bedrock conditions of the whole reservoir boundary is seldom performed when designing a dam. In this study, a variety of investigations and analyses have been conducted to reveal a seepage phenomenon through a reservoir boundary composed of highly fractured metamorphic rocks at the Daechung multipurpose dam. At the study site, groundwater levels at monitoring wells located close to a reservoir tend to change proportionally to reservoir water levels, usually with a rapid response time of 1 day or less. Soil moisture content also changes with respect to the reservoir water level, and the area where seepage from the reservoir is a possibility has a relatively high soil moisture content. The similarity of measured seepage rates at the outflow site and the seepage rate estimated by Darcy’s law suggests strong connectivity and high density of the fractures. The estimated seepage rate using a numerical model for the northernmost valley (Zone 1) is approximately 127.2 m³/day in the case of high reservoir water level and 24.3 m³/day in the case of low water level. Continuous monitoring to obtain time series data for water levels, quality, and bedrock displacement is recommended to assess the sustainable stability of this geologic barrier.     

大区域地下水流数值模拟研究现状及存在问题

在分析大区域地下水流数值模型构建缘起的前提下,系统论述了近年来地下水流数值模拟在大区域地下水资源评价、水文地质参数确定、地面沉降、溶质运移、海水入侵、盐渍化、风险评估、地下水管理及地表水与地下水的联合开发利用等方面的国内外研究应用现状;归纳、总结了目前大区域地下水流数值模型在灵敏度分析、裂隙和岩溶介质中模型建立、基于地下水流数值模拟的溶质运移模型建立、地下水流数值模型构建所需工作量等理论和方法研究及实际建模过程中存在的一些问题;展望了今后大区域地下水流数值拟在研究范围、模拟技术与方法以及与其它模型耦合等方面的发展趋势。     

An assessment of the effect of urban development on groundwater levels in a chalk aquifer

Underlying the site of a proposed development is a chalk aquifer, groundwater levels are close to the surface. The storm water from the development is to be drained into a lake in the center of the development. Because of the high groundwater levels the effect of this lake has been studied by means of a simple localized mathematical model. It is shown that such a model can give results of sufficient accuracy with regard to probable changes in groundwater levels caused by the development.     

GMS在双城市城区地下水资源评价中的应用

根据双城市水文地质条件建立了概念模型,应用GMS软件建立了研究区地质结构模型及地下水数值模拟模型。考虑自然条件以及开采量的影响,设计6种方案对研究区地下水流进行预报,结果显示以设计开采量对水源地进行开采,水源地投产10年后最大中心水位降深不会超过最大允许降深。     

Arsenic-rich groundwater in an urban area experiencing drought and increasing population density,Perth, Australia

Groundwater in the Gwelup groundwater management area in Perth, Western Australia has been enriched in As due to the exposure of pyritic sediments caused by reduced rainfall, increased groundwater abstraction for irrigation and water supply, and prolonged dewatering carried out during urban construction activities. Groundwater near the watertable in a 25–60 m thick unconfined sandy aquifer has become acidic and has affected shallow wells used for garden irrigation. Arsenic concentrations up to 7000 μg/L were measured in shallow groundwater, triggering concerns about possible health effects if residents were to use water from household wells as a drinking water source. Deep production wells used for public water supply are not affected by acidity, but trends of progressively increasing concentrations of Fe, SO₄ and Ca over a 30-a period indicate that pyrite oxidation products extend to the base of the unconfined aquifer. Falling Eh values are triggering the release of As from the reduction of Fe(III) oxyhydroxide minerals near the base of the unconfined aquifer, increasing the risk that groundwater used as a drinking water source will also become contaminated with high concentrations of As.     

基于数值模型的地下水污染预警方法研究

地下水是中国许多城市主要的供水水源,目前中国部分城市地下水已受到不同程度的污染,导致地下水资源供需矛盾日益突出。进行地下水污染预警是保护地下水资源的一个有效措施,当前国内外相关研究刚刚起步,有关预警理论、方法和技术框架仍未形成一套完善的体系。本文简述了地下水污染预警的研究现状及存在的不足,并以中国北方某铬渣场地为例,根据当地的水文地质条件,利用数学模型建立了地下水污染预警模型,给出了不同等级的地下水污染预警分区,研究结果可为当地地下水污染防治和地下水污染控制规划提供科学依据。