Assessment of groundwater inflow in urban territories

Analytical and numerical methods are proposed for the calculation of water inflow into construction pits under various geological—engineering and hydrogeological conditions at the construction site. Water inflow into the pit is shown to depend not only on lateral seepage but also on the leakage from underlying aquifers at appropriate parameters of their interaction. Under certain natural conditions, the most efficient method for construction pit draining at low water yield of soils in the construction area are light wellpoint systems, the capacity and layout of which is determined by the potential inflow through the pit contour. The results of analytical and numerical calculations for the assessment of groundwater inflow into a pit are given, and light wellpoint systems are shown to be effective under different combinations of natural and engineering conditions.     

A variety of natural systems of industrial groundwater on Siberian platform

The lithologic-genetic formation conditions of a reservoir of industrial groundwater on Siberian Platform, associated with the existence of a bank reef in the Cambrian. Within this cryohydrogeological structure, the properties and reserves of the hydromineral stock that can be developed parallel to the diamond-mining on Udachnaya pipe without significant environmental damage.     

Assessment of the natural resources of groundwater by using balance-hydrodynamic models

The specific features of formulation and implementation of balance-hydrodynamic simulation during different-scale studies of natural resources of groundwater. Are an example of detailed estimate of the resources and balance of groundwater in the Vologda River basin is given. It is noted that the use of balance-hydrodynamic models, in addition to an increase in the general reliability of estimates, allows the calculation of normal annual characteristics of groundwater resources with different occurrence (exceedance probability), which is impracticable when hydrodynamic methods in other formulations are used.     

Large-scale mapping of neotectonics of platform territories: Case study of Moscow

The experience in large scale (1: 50000–1: 10000) neotectonic mapping of platform areas is discussed. The structural characteristics of the geological environment (the large size of major structural forms, the extremely low gradients, speeds, and the amplitudes of the most recent and modern tectonic movements, etc.) cause some difficulties for their cartographic representation. A considerable part of legends of neotectonic maps of platforms mostly reflect the geomorphologic component, which is an indirect indicator to the most recent structures and, in essence, such maps are geomorphologic-neotectonic. The large-scale neotectonic mapping requires a comprehensive analysis of the nature and age of all significant elements of earth surface topography and the structure of Cenozoic deposits, the identification of the regularities in their space and time development that can be caused by and attributed to geodynamic factors. Such studies must be based on materials of medium- and small-scale generalizations.     

Influence of partial confinement and Holocene river formation on groundwater flow and dissolution in the Florida carbonate platform

Much of what is known about groundwater circulation and geochemical evolution in carbonate platforms is based on platforms that are fully confined or unconfined. Much less is known about groundwater flow paths and geochemical evolution in partially confined platforms, particularly those supporting surface water. In north‐central Florida, sea level rise and a transition to a wetter climate during the Holocene formed rivers in unconfined portions of the Florida carbonate platform. Focusing on data from the Santa Fe River basin, we show river formation has led to important differences in the hydrological and geochemical evolution of the Santa Fe River basin relative to fully confined or unconfined platforms. Runoff from the siliciclastic confining layer drove river incision and created topographic relief, reorienting the termination of local and regional groundwater flow paths from the coast to the rivers in unconfined portions of the platform. The most chemically evolved groundwater occurs at the end of the longest and deepest flow paths, which discharge near the center of the platform because of incision of the Santa Fe River at the edge of the confining unit. This pattern of discharge of mineralized water differs from fully confined or unconfined platforms where discharge of the most mineralized water occurs at the coast. Mineralized water flowing into the Santa Fe River is diluted by less evolved water derived from shorter, shallower flow paths that discharge to the river downstream. Formation of rivers shortens flow path lengths, thereby decreasing groundwater residence times and allowing freshwater to discharge more quickly to the oceans in the newly formed rivers than in platforms that lack rivers. Similar dynamic changes to groundwater systems should be expected to occur in the future as climate change and sea level rise develop surface water on other carbonate platforms and low lying coastal aquifer systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Regularities in the formation of groundwater infiltration recharge

The effect of meteorological, landscape, geological-pedological, and hydrogeological factors on the formation of total water balance and infiltration recharge of groundwater. The results of analysis of calculated mean annual and within-year values of water balance elements on land surface and in the vadose zone were used to identify some regularities, governing the resulting input of moisture to groundwater table at different depth of its occurrence (infiltration).     

Modelling the impact of extensive irrigation on the groundwater resources

Drastic groundwater resource depletion due to excessive extraction for irrigation is a major concern in many parts of India. In this study, an attempt was made to simulate the groundwater scenario of the catchment using ArcSWAT. Due to the restriction on the maximum initial storage, the deep aquifer component in ArcSWAT was found to be insufficient to represent the excessive groundwater depletion scenario. Hence, a separate water balance model was used for simulating the deep aquifer water table. This approach is demonstrated through a case study for the Malaprabha catchment in India. Multi‐site rainfall data was used to represent the spatial variation in the catchment climatology. Model parameters were calibrated using observed monthly stream flow data. Groundwater table simulation was validated using the qualitative information available from the field. The stream flow was found to be well simulated in the model. The simulated groundwater table fluctuation is also matching reasonably well with the field observations. From the model simulations, deep aquifer water table fluctuation was found very severe in the semi‐arid lower parts of the catchment, with some areas showing around 60 m depletion over a period of eight years. Copyright © 2012 John Wiley & Sons, Ltd.     

辽宁省数字化形变观测自然干扰分析

对数字形变观测过程中辽宁丹东地震台、营口地震台、抚顺地震台、朝阳地震台DSQ水管仪、SS-Y伸缩仪存在的自然干扰现象进行研究,对其机理和数据形态作了对比分析,为快速、准确地判别自然干扰提供了科学依据。     

Evaluation of groundwater resources in wide inundation areas of the Mekong River basin

Severe floods can have disastrous impacts and cause wide ranging destruction in the Mekong River basin. At the same time groundwater resources are significantly influenced and extensively recharged by flood water in inundation areas of the basin. This study determines the variation of groundwater resources caused by flooding over inundated areas located in lower part of the Mekong River basin using numerical modeling and field observations. The inundation calculations have been evaluated using satellite image outputs. Comparing large, medium and small flood events, we conclude that flood control which reduces the area of inundation, results in a reduction of groundwater resources in the area. In 1993, a 19% reduction in inundation areas resulted in a 31% reduction in groundwater storage. In 1998, a 44% reduction in inundation areas led to a 42% reduction in groundwater storage. Thus, while flood control activities are vital to reduce negative flood impacts in the Mekong River basin, they also negatively impact groundwater resources in the area.     

Integration of surface water with groundwater resources aided by numerical modelling

ABSTRACT

The possibility was studied of a gradual extension of the irrigable area of the Tarlac Irrigation System, located in the alluvial plain of Luzon Island (Philippines). The extension would be made by integrating groundwater with surface water supplied from a reservoir already designed. Aquifer exploitation was studied adopting the criterion that groundwater is a very expensive resource to be turned to only in severe drought years. The objectives of the study were twofold: (a) planning the distribution of the wells (to be drilled during the various stages of the irrigation system development) so as to minimize the pumping cost; (b) establishing a policy for the well management in conjunction with the reservoir operation. Different schemes of the combined system management were analysed on the basis of the climatic and hydrological regime over the period 1950–1972. For this period the monthly water requirements for the different crops and the monthly values of aquifer recharge were computed. The economic analyses were performed using present prices of agricultural products and power together with several different hypotheses about future prices. A finite element model of the semiconfined aquifer was postulated and calibrated; the importance of the return flow from irrigation was also tested. Simulations of exploitation schemes provided a detailed forecast of the aquifer response to the irrigation demands.     

Imaging of groundwater resources in glacial deposits using high-resolution reflection seismics, Sweden

Two high-resolution reflection seismic profiles were acquired in the Heby area of eastern Sweden over glacial deposits for the purpose of mapping groundwater resources. The majority of shot points were located in clay resulting in good quality data along most of the profiles. On stacked and migrated sections, the uppermost clay is about 20 m thick and is characterized by its subhorizontal reflectivity. Sand/gravel deposits below it contain more dipping interfaces and have a chaotic reflectivity pattern. Depth to bedrock is interpreted to be 90 and 65 m on the respective profiles and occurs in about a 100-m-wide trough on both profiles. Reflections from the tops of sandy gravel zones generally have higher amplitudes. Clear reflections from a thin silt layer (20 cm thick) at about 10-m depth are observed on one of the profiles. Elastic finite difference modeling and the observation of this reflection in shot gathers show that the reflection is not an artifact of the acquisition nor the processing. The modeling also shows that there is no marked low-velocity waveguide in the near surface, but that an effective low Q zone may be present. Comparison with refraction profiling on the other profile shows that there is better agreement between the reflection seismic results and penetration tests than the refraction results with these tests. Both profiles allow the thickness of the overlying clay layers to be determined, as well as the thickness of the underlying sand/gravel deposits. This is important for estimating the amount of groundwater resources in an area.     

Origin and dynamics of groundwater salinity in the alluvial plains of western Delhi and adjacent territories of Haryana State,India

Groundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the alluvial plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide–chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human‐induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water‐level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright © 2011 John Wiley & Sons, Ltd.     

Modelling of groundwater mound formation resulting from transient recharge

An analytical solution of a linearized Boussinesq equation is obtained to predict water table fluctuations as a result of time varying recharge from a strip basin for any number of recharge cycles. The analytical solution is obtained by using finite Fourier sine transform. Applications of the solution for the prediction of water table fluctuations and sensitivity analysis are demonstrated with the help of example problems. Copyright © 2001 John Wiley & Sons, Ltd.     

Characterization of the groundwater flow regime and hydrochemistry of groundwater from the Buem formation,Eastern Ghana

This study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in Ghana. Q‐mode hierarchical cluster analysis (HCA) was applied to 57 hydrochemical data from the Buem formation in the northern part of the Volta Region in Ghana. R‐mode HCA and R‐mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation. Results of both the Q‐ and R‐mode analyses were backed by graphical methods. The analyses revealed two major water types, differentiated by salinity levels into four spatial groundwater associations. The characteristics of the four groundwater types are discussed. The recharge areas are characterized by Ca? HCO₃ low salinity waters which evolve through rock–water interactions to Na? HCO₃ high salinity waters in the discharge areas. This study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals, principally silicates in the aquifer matrix. The effects of the chemistry of recharging precipitation are higher in the recharge areas, while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime. All the four spatial groundwater associations have low sodium content, but salinity levels increase towards the discharge areas, such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants. Copyright © 2011 John Wiley & Sons, Ltd.     

地热井的天然源超低频电磁探测影响因素分析

本文使用天然源超低频电磁探测仪对北京大学校园内两口地热井进行了超低频电磁探测试验,获得了1号地热井（京热119号井）连续五天、每天四个时刻的天然源超低频电磁探测数据以及2号地热井（京热168号井）单天的天然源超低频探测的数据.基于所获得的数据,开展了地热井的天然源超低频探测影响因素的研究,这些因素主要包括：天然源超低频电磁场和观测时间的关系、探头摆放方向与接收工频谐波干扰关系以及天气状况对观测数据质量的影响等.研究表明：(1)天然源超低频电磁探测信号存在明显的日夜交替变化,其中相对振幅-频率曲线在不同日期、同一邻近时刻总体的包络线具有较好的重复性和一定的稳定性;(2)工频谐波干扰场方向是影响因素之一,当仪器探头长轴方向与工频谐波干扰场的等效主轴方向平行时噪声影响最小;(3)雨天环境会对天然场源超低频信号中的高频部分造成较大影响.     

Changing drainage patterns in a semi-arid area and their effects on groundwater resources

The magnitude of groundwater resources is poorly correlated with surface catchment area in a group of wadi bottom alluvial aquifers in Northern Oman. It is suggested that this is due to progressive water gap captures across a limestone ridge.     

淄博市王旺庄水源地地下水开采预测的数值模拟

王旺庄水源地是淄博市晴纶工程的后备水源地,设计供水能力20000m^2／d。利用Ritz有限元数值分析方法。结合单纯性线性规划,在完成了对山东省淄博市临淄区王旺庄一朱台地段的淄博市腈纶工程水源地的水文地质模型建造的基础上,成功地对水源地进行地下水开采模拟,同时对该水源地的未来10年开采作了两种大气降水条件下的地下水动态预测。为腈纶工程水源地地下水开采提供了充分的设计依据。     

江西省主要城市地下水资源及应急水源地遴选

江西各主要城市都是临水系而建,地表水资源是城市集中供水的主要水源。但是,为了应对突发事件很有必要在城市及其周边规划和遴选应急地下水源地。该文在分析阐述了各主要城市水文地质条件和地下水资源特征后．根据应急水源地的遴选原则,在全省11个主要城市中,确定了29个应急地下水源地,其可采资源总量为74781．372×10^4m^3／a。     

Geomorphic controls of perched groundwater interaction with natural ridge-top depressional wetlands

Geographically isolated wetlands (GIWs) are commonly reported as having hardpan or low hydraulic conductivity units underneath that produce perched groundwater, which can sustain surface water levels independently of regional aquifer fluctuations. Despite the potential of GIW-perched aquifer systems to provide important hydrological and ecological functions such as groundwater storage and native amphibian habitat, little research has studied the hydrologic controls and dynamics of these systems. We compared several ridge-top depressional GIW-perched groundwater systems to investigate the role of watershed morphology on hydroregime and groundwater-surface water interaction. Ridge-top depressional wetlands in the Daniel Boone National Forest, Kentucky were chosen because they offer natural controls such as lack of apparent connection to surface water bodies, similar climate, and similar soils. Three wetlands with different topographic slopes and hillslope structures were mapped to distinguish key geomorphic parameters and monitored to characterize groundwater-surface water interaction. Wetlands with soil hummocks and low upland slopes transitioned from infiltration to groundwater discharge conditions in the spring and during storm events. The magnitude and duration of this transition fell along a continuum, where higher topographic slopes and steeper uplands produced comparably smaller and shorter head reversals. This demonstrates that ridge-top GIW-perched groundwater systems are largely sensitive to the runoff-recharge relationship in the upland area which can produce significant groundwater storage on a small-scale.     

Experimental studies in natural groundwater recharge dynamics: Assessment of recent advances in instrumentation

To quantify and model the natural groundwater-recharge process, two sites in south-central Kansas, U.S.A., were instrumented with various modern sensors and data microloggers. The atmospheric-boundary layer and the unsaturated and saturated soil zones were monitored as a unified regime. Data from the various sensors were collected using microloggers in combination with magnetic-cassette tape, graphical and digital recorders, analog paper-tape recorders, and direct observations to evaluate and automate data collection and processing.

Atmospheric sensors included an anemometer, a tipping-bucket raingage, an air-temperature thermistor, a relative-humidity probe, a net radiometer, and a barometric-pressure transducer. Sensors in the unsaturated zone consisted of soil-temperature thermocouples, tensiometers coupled with pressure transducers and dial gages, gypsum blocks, and a neutron moisture probe operated by an observer. The saturated-zone sensors consisted of a water-level pressure transducer, a conventional float gage connected to a variable potentiometer, soil thermocouples, and a number of multiple-depth piezometers.

Evaluation of the operation of these sensors and recorders indicated that certain types of equipment such as pressure transducers are very sensitive to environmental conditions. Extraordinary steps had to be taken to protect some of the equipment, whereas other equipment seemed to be reliable under all conditions. Based on such experiences, a number of suggestions aimed at improving such investigations are outlined.