煤层顶板承压含水层涌水模式与疏放水钻孔优化设计

针对煤层顶板承压含水层涌水模式不清的问题,从煤层回采过程中顶板含水层涌水的时空变化特征入手,提出顶板含水层涌水量由静态储存量和动态补给量构成,认为静态储存量主要受来压步距、顶板垮落和导水裂隙(合称冒裂)影响区含水层厚度、含水层给水度控制,动态补给量主要受冒裂影响区外围含水层厚度、渗透性流场中水力梯度和过水断面面积控制;根据导水裂隙波及含水层情况,将顶板含水层涌水模式划分为井底进水的触及井涌水、井壁及井底进水的非完整井涌水和井壁进水的完整井涌水3种模式,并基于地下水渗流理论给出不同涌水模式下动态补给水量计算公式;针对以往疏放水钻孔数量多及疏放水量大的问题,以实现工作面顶板含水层静态储存量疏放后动态补给量可控为目的,提出冒裂区高度控制钻孔深度、单孔水位影响半径控制钻孔布置间距、钻孔疏放水量稳定时间控制超前疏放时间的疏放水钻孔优化设计理念,对疏放水及疏放钻孔布置进行优化,形成系统的顶板含水层水疏放体系。研究结果丰富了煤层顶板含水层涌水量计算和控制方法,对顶板水害防控具有实际的指导意义。      

Artificial recharge of groundwater: hydrogeology and engineering

Artificial recharge of groundwater is achieved by putting surface water in basins, furrows, ditches, or other facilities where it infiltrates into the soil and moves downward to recharge aquifers. Artificial recharge is increasingly used for short- or long-term underground storage, where it has several advantages over surface storage, and in water reuse. Artificial recharge requires permeable surface soils. Where these are not available, trenches or shafts in the unsaturated zone can be used, or water can be directly injected into aquifers through wells. To design a system for artificial recharge of groundwater, infiltration rates of the soil must be determined and the unsaturated zone between land surface and the aquifer must be checked for adequate permeability and absence of polluted areas. The aquifer should be sufficiently transmissive to avoid excessive buildup of groundwater mounds. Knowledge of these conditions requires field investigations and, if no fatal flaws are detected, test basins to predict system performance. Water-quality issues must be evaluated, especially with respect to formation of clogging layers on basin bottoms or other infiltration surfaces, and to geochemical reactions in the aquifer. Clogging layers are managed by desilting or other pretreatment of the water, and by remedial techniques in the infiltration system, such as drying, scraping, disking, ripping, or other tillage. Recharge wells should be pumped periodically to backwash clogging layers. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s10040-001-0182-4. Electronic Publication     

Groundwater supply and demand from southern Africa’s crystalline basement aquifer: evidence from Malawi

Failure of borehole sources in weathered and fractured crystalline basement aquifers in Malawi in southern Africa has been linked with poor borehole design, mechanical failure and badly sited boreholes. However, recent work in Malawi indicates that demand may now exceed long-term resource potential in some places and that this is also a cause of water point failure. An 11-year climate cycle (including a wet and dry period) necessitates overdraft from groundwater storage during the dry-cycle years before episodic rainfall events in the wetter part of the cycle again recharge the aquifers. Data, particularly groundwater hydrograph data, are sparse, but sufficient to evaluate the long-term renewable groundwater potential for both fractured and weathered basement-aquifer types in each of the 15 management areas in Malawi. The groundwater potential or long-term renewable resource (recharge) is given by the sum of Darcian throughflow and dry-season depletion of storage. Estimated rural demand exceeds the renewable resource in the fractured-rock aquifer in two management units and in the weathered-rock aquifer in two other units. Although there is inherent uncertainty in the water-balance estimates, the likelihood that rural demand is exceeding long-term average recharge in some areas is cause for concern.     

Groundwater recharge of carbonate aquifers of the Silesian-Cracow Triassic (southern Poland) under human impact

A Triassic carbonate unit has been intensively drained by zinc and lead ore mines and numerous borehole fields since the nineteenth century. Its groundwater recharge has increased due to: pumping of water from boreholes, mining activity, and urbanization. An approach to determine the amounts of the recharge at a variety of spatial scales is presented in the paper. Different methods were used to identify and quantify recharge components on a regional and local scale: mathematical modelling was performed for four aquifers included in an aquifer system, an analytical estimation based on the assumption that an average recharge is equal to the average discharge of the hydrogeological system—for six man-made drainage centres, and the method of water level fluctuation (WLF) was applied in one observation borehole. Results of modelling have been supplemented by observation of environmental tracers (δ¹⁸O, δ²H, ³H), noble gases temperatures, and ⁴He_exc in groundwater. The regional aquifer’s current recharge according to estimations performed by means of modelling varies from 39 to 101 mm/year on average. Depending on the aquifer site the average precipitation ranges from 779 to 864 mm/year. In the confined part of the aquifer average recharge ranges from 26 to 61 mm/year. Within outcrops average recharge varies from 96 to 370 mm/year. Current recharge estimated by the analytical method for man-made drainage centres varies from 158 up to 440 mm/year. High values are caused by different recharge sources like precipitation, induced leakage from shallow aquifers, and water losses from streams, water mains and sewer systems. Pumping of water, mining and municipal activities constitute additional factors accounting for the intensified recharge.     

大清河流域平原区地下水人工补给潜力与补给方式分析

为了有效提升大清河流域平原区地下水水位,亟需在此区域开展地下水人工补给工程,并确定合理的建设位置及有效的补给方式。首先基于研究区可利用补给水源、地下水位、地表高程、地表坡度及与河道距离5个指标的分布特征,构建地下水补给潜力评价体系,采用ArcGIS空间分析功能对研究区进行了地下水人工补给潜力区划;然后在此评价体系基础上,在典型人工补给高潜力区进一步开展系列野外现场试验,探讨适宜可行的地下水人工补给方式。结果表明：研究区西北部及南部河道附近区域开展人工补给工程潜力较高,而中部、北部及西南部远离河道的区域潜力较低。高潜力区——白沟引河地段包气带及含水层渗透性良好,整体渗透系数均在5 m/d左右或更高,适宜地表补给,但河床渗透性较差,渗透系数基本在0.01~0.09 m/d间,若通过河道补给需配合清淤等措施。其中,在上游及中游沿岸适宜将河道水通过生态水渠引至修建的地表入渗池或借助天然渗坑内入渗补给,在中下游沿岸区域适宜将补给水进行严格的水处理后采用井灌方式补给,在白沟引河中下游河道适宜修建拦水坝,利用河道进行入渗补给。     

Methodology to evaluate the renewal period of carbonate aquifers: a key tool for their management in arid and semiarid regions,with the example of Becerrero aquifer,Spain

A methodological procedure is proposed for determining the renewal period (RP), which expresses the ratio of total storage to recharge of carbonate aquifers, and it was applied to the overexploited moderate-size Becerrero carbonate aquifer (southern Spain). To this end, geological and subsurface data—time domain electromagnetic (TEM) soundings and borehole logs—were integrated to construct a three-dimensional (3D) geological model of the aquifer. The interconnected porosity was estimated by analyzing 73 rock samples. The resulting 3D geometrical model makes it possible to quantify the fractions of the aquifer having a confined or unconfined behaviour. Based on the total storage capacity (179?·?10⁶–514?·?10⁶ m³) and available aquifer recharge estimation (4.8?·?10⁶–6.4?·?10⁶ m³/year), an RP between 37 and 106 years is obtained. In view of the RP, an exploitation rate slightly lower than the average recharge of the system is recommended, so that the piezometric level will be stable but below the discharge head that is produced through the springs in natural conditions. The proposed methodology to obtain an aquifer RP and the management strategies designed accordingly are of broad interest, especially for carbonate aquifers, which are abundant in arid and semiarid regions.     

Quantification of groundwater recharge and river bed clogging by daily water level measurements in a check dam

Check dams are one of the methods of managed aquifer recharge to augment groundwater storage in regions with non-perennial rivers. The objectives of this study were to quantify the groundwater recharge from a check dam in the Arani River, north of Chennai, India, and to assess the clogging of the riverbed. The water level in the check dam was measured daily for 3 years from 2010 to 2013. Other field investigations carried out include measurement of the topographic elevation of the riverbed using the differential global positioning system. Based on the water balance method, the quantity of water evaporated and recharged was estimated. A comparison of 3-year daily water level measurements indicated that there is no clogging in the riverbed during the study period, as this check dam is fitted with a sluice gate which is operated at appropriate times to flush out the sediments.     

Aquifer storage and recharge: Innovation in water resources management

Stormwater and treated sewerage effluent, previously regarded as waste, are now being reused in South Australia through the innovative aquifer storage and recharge technique. After pretreatment in wetlands, this water is stored in otherwise unused brackish aquifers for summer irrigation of parklands. Trials are underway using recycled water from the Bolivar Wastewater Treatment Plant for irrigation of market gardens. This paper presents several case studies where the aquifer storage and recharge technique has been successful, with savings in water and infrastructure costs, as well as providing environmental benefits.     

吉林省西部潜水资源与生态环境风险分析

吉林省西部是我国主要粮食产区,但区内农业水利规划管理同时面临潜水资源与生态环境双重风险。近20年来,区内曾尝试多种水资源利用模式,但缺少不同模式应用效果的定量化对比。文章建立了不同水资源利用模式,对比分析各模式的水资源与次生盐碱化风险。以洮儿河流域为例,采用循环神经网络预测2019—2023年该地区大气降水和地表水对地下水补给量;通过随机数值模拟预测现状开采、连续干旱、无序开采、地下水库建设、节水灌溉、旱田改水田6种情形下,区内潜水水位空间分布特征。以防止次生盐碱化为目标,定义水位埋深上限为1 m;以含水介质厚度为参考,定义水位埋深下限为12 m。遴选适合吉林省西部地区地下水资源可持续利用模式。结果显示:无序开采是导致区内水资源枯竭的主要诱因;地下水库建设和旱改水工程有助于潜水资源维护,但长期运行可加剧生态环境风险。节水灌溉（净采强度为2.0×108～3.0×108 m3/a）是降低区内水资源风险和生态环境风险的最佳方式。文章采用的神经网络—随机模拟分析方法成功预测了地下水位变化驱动因子和地下水位中长期变化趋势,为我国干旱半干旱地区潜水资源利用方案制定提供了新方法。     

Percolation pond as a method of managed aquifer recharge in a coastal saline aquifer: A case study on the criteria for site selection and its impacts

Percolation ponds have become very popular methods of managed aquifer recharge due to their low cost, ease of construction and the participation and assistance of community. The objective of this study is to assess the feasibility of a percolation pond in a saline aquifer, north of Chennai, Tamil Nadu, India, to improve the storage and quality of groundwater. Electrical resistivity and ground penetrating radar methods were used to understand the subsurface conditions of the area. From these investigations, a suitable location was chosen and a percolation pond was constructed. The quality and quantity of groundwater of the nearby area has improved due to the recharge from the pond. This study indicated that a simple excavation without providing support for the slope and paving of the bunds helped to improve the groundwater quality. This method can be easily adoptable by farmers who can have a small pond within their farm to collect and store the rainwater. The cost of water recharged from this pond works out to be about 0.225 Re/l. Cleaning the pond by scrapping the accumulated sediments needs to be done once a year. Due to the small dimension and high saline groundwater, considerable improvement in quality at greater depths could not be achieved. However, ponds of larger size with recharge shafts can directly recharge the aquifer and help to improve the quality of water at greater depths.     

Evaluating the salinity distribution of a shallow coastal aquifer by vertical multielectrode profiling (Denmark)

A monitoring system, including five groups of piezometers and five vertical multielectrode profiling probes (VMEP), has been installed in an aquifer beneath a coastal dune in Denmark. In order to assess the salinity distribution within the aquifer, geoelectrical data were gathered in March, June and September 2008, by measuring a dipole-dipole and gradient array using multielectrode profiling. Interpretation of the processed resistivity data was performed by regularized inversion using a one-dimensional, horizontally layered model of formation resistivity. The standard deviation on estimated layer log-resistivity was 0.01–0.03. By estimating two parameters of a power function, observed fluid conductivities derived from samples of porewater were related to corresponding estimated formation resistivities. The conductivity profiles correlate with a winter situation in March with high sea level, active recharge and significant wave activity, causing increased hydraulic heads, a thicker freshwater lens and salt water overlying freshwater close to the sea. In June, the thickness of the freshwater lens is reduced due to less recharge and prevailing offshore winds, imposing density-stable conditions and a sharper transition between fresh and brackish water. During the autumn, aquifer recharge is enhanced and hydraulic heads increase, resulting in a thicker freshwater lens.     

Ion exchange and trace element surface complexation reactions associated with applied recharge of low-TDS water in the San Joaquin Valley,California

Stable isotope data, a dissolved gas tracer study, groundwater age dating, and geochemical modeling were used to identify and characterize the effects of introducing low-TDS recharge water in a shallow aerobic aquifer affected by a managed aquifer recharge project in California’s San Joaquin Valley. The data all consistently point to a substantial degree of mixing of recharge water from surface ponds with ambient groundwater in a number of nearby wells screened at depths above 60 m below ground surface. Groundwater age data indicate that the wells near the recharge ponds sample recently recharged water, as delineated by stable O and C isotope data as well as total dissolved solids, in addition to much older groundwater in various mixing proportions. Where the recharge water signature is present, the specific geochemical interactions between the recharge water and the aquifer material appear to include ion exchange reactions (comparative enrichment of affected groundwater with Na and K at the expense of Ca and Mg) and the desorption of oxyanion-forming trace elements (As, V, and Mo), possibly in response to the elevated pH of the recharge water.     

Study on the hydraulic parameter differences between pumping and recharge in a confined aquifer of a soft soil area

Artificial recharge is an effective remediation measure for controlling groundwater level and subsidence in many coastal cities in China. Hydraulic parameters estimated by pumping tests are often used in the design of both pumping and recharge systems. However, the hydraulic parameters in the recharge process have been found to differ from those in the pumping process and should be studied in greater detail. Eight single-well pumping and recharge tests were conducted within a confined aquifer in a soft soil area in the city of Tianjin, and the differences in wellbore storage influences and well losses between the recharge and pumping processes were examined. Furthermore, based on the Hantush and Jacob model, an algorithm combining the Levenberg–Marquardt algorithm (LMA) and genetic algorithm (GA) was employed for estimation of the hydraulic parameters. The results illustrated that the combined algorithm eliminating wellbore storage influences could provide hydraulic parameters from which the groundwater level variation could be accurately simulated. The hydraulic conductivity and specific storage values obtained in the pumping tests were higher than those obtained in the recharge tests. In addition to slight plugging of the recharge well, the specific storage differences could be explained by the compression and rebound deformation characteristics of sand in the confined aquifer. The specific storage estimated by pumping tests should be adjusted when applied in groundwater recharge calculation.

     

Contamination risk and drinking water protection for a large-scale managed aquifer recharge site in a semi-arid karst region,Jordan

Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especially during winter seasons when extremely variable rainfall of high intensities prevails. An additional challenge is posed when managed recharge of storm water is applied, since karst aquifers display a high spatial variability of hydraulic properties. In these cases, adapted protection concepts are required to address the interaction of surface water and groundwater. In this study a combined protection approach for the surface catchment of the managed aquifer recharge site at the Wala reservoir in Jordan and the downstream Hidan wellfield, which are both subject to frequent bacteriological contamination, is developed. The variability of groundwater quality was evaluated by correlating contamination events to rainfall, and to recharge from the reservoir. Both trigger increased wadi flow downstream of the reservoir by surface runoff generation and groundwater seepage, respectively. A tracer test verified the major pathway of the surface flow into the underground by infiltrating from pools along Wadi Wala. An intrinsic karst vulnerability and risk map was adapted to the regional characteristics and developed to account for the catchment separation by the Wala Dam and the interaction of surface water and groundwater. Implementation of the proposed protection zones for the wellfield and the reservoir is highly recommended, since the results suggest an extreme contamination risk resulting from livestock farming, arable agriculture and human occupation along the wadi. The applied methods can be transferred to other managed aquifer recharge sites in similar karstic environments of semi-arid regions.     

The effect of typical geological heterogeneities on the performance of managed aquifer recharge: physical experiments and numerical simulations

Understanding the role of geological heterogeneity on the performance of managed aquifer recharge (MAR) in terms of effective groundwater storage is crucial to design MAR systems. Natural aquifers are affected by a variety of geologic strata and structures at different scales, which are responsible for wide ranging hydraulic properties. This study combines physical experiments and numerical modeling to investigate the effect of geologic structures commonly encountered in sedimentary environments, on MAR-induced groundwater flow patterns using injection wells. Models were conceptualized and parametrized based on the hydrogeological conditions of Tailan River basin in arid NW China, which hosts a typical, structurally complex, alluvial-fan aquifer system affected by sediment layering, clay lenses and anticline barriers, and is extensively studied for the strategic potential of MAR in addressing water shortages in the region. Results showed that, compared to a homogeneous scenario, high-permeability aquifer layers shortened groundwater ages, decreased the thickness of the artificially recharged water lenses (ARWLs), and shifted the stagnation points downstream. Clay lenses increased groundwater residence times but had little effect on spatial flow patterns due to their elongation parallel-to-flow direction. Overall groundwater ages, as well as the thickness of ARWLs created through injection on the upstream side of an anticline, increased, and this to a larger extent than through injection on the downstream side, which did not increase significantly compared to the homogeneous scenario. Results provide insights for MAR optimization in naturally heterogeneous aquifer systems, along with a benchmark tool for application to a wide range of typical geological conditions.

     

用有限混合网络模型计算天津地热田热水量

针对因地热水位动态资料不足而导致的水量计算结果偏离实际的状况，以天津地热田雾迷山组热储层为例，建立了利用放射性同位素^14C资料进行地热水量计算的有限混合网络模型，并利用1998—2001年的水位、水量及^14C资料进行了模型的识别，得到了有效孔隙度和弹性释水率等水文地质参数，利用所建立的模型及水文地质参数计算了地热水的储存量及补给量。研究表明，地热水的开采主要是消耗弹性储量。     

Artificial groundwater recharge to a semi-arid basin: case study of Mujib aquifer,Jordan

Mujib watershed is an important groundwater basin which is considered a major source for drinking and irrigation water in Jordan. Increased dependence on groundwater needs improved aquifer management with respect to understanding deeply recharge and discharge issues, planning rates withdrawal, and facing water quality problems arising from industrial and agricultural contamination. The efficient management of this source depends on reliable estimates of the recharge to groundwater and is needed in order to protect Mujib basin from depletion. Artificial groundwater recharge was investigated in this study as one of the important options to face water scarcity and to improve groundwater storage in the aquifer. A groundwater model based on the MODFLOW program, calibrated under both steady- and unsteady-state conditions, was used to investigate different groundwater management scenarios that aim at protecting the Mujib basin. The scenarios include variations of abstraction levels combined with different artificial groundwater recharge quantities. The possibilities of artificial groundwater recharge from existing and proposed dams as well as reclaimed municipal wastewater were investigated. Artificial recharge options considered in this study are mainly through injecting water directly to the aquifer and through infiltration from reservoir. Three scenarios were performed to predict the aquifer system response under different artificial recharge options (low, moderate, and high) which then compared with no action (recharge) scenario. The best scenario that provides a good recovery for the groundwater table and that can be feasible is founded to be by reducing current abstraction rates by 20% and implementing the moderate artificial recharge rates of 26 million(M)m³/year. The model constructed in this study helps decision makers and planners in selecting optimum management schemes suitable for such arid and semi-arid regions.     

Hydrochemical variation in the springs water between Jerusalem–Ramallah Mountains and Jericho Fault,Palestine

The spatial and temporal changes of the composition of the groundwater from the springs along the Wadi Qilt stream running from the Jerusalem–Ramallah Mountains towards the Jericho Plain is studied during the hydrological year 2006/2007. The residence time and the intensity of recharge play an important role in controlling the chemical composition of spring water which mainly depends on distance from the main recharge area. A very important factor is the oxidation of organics derived from sewage and garbage resulting in variable dissolved CO₂ and associated HCO₃ ⁻ concentration. High CO₂ yields lower pH values and thus under-saturation with respect to calcite and dolomite. Low CO₂ concentrations result in over-saturation. Only at the beginning and at the end of the rainy season calcite saturation is achieved. The degradation of dissolved organic matter is a major source for increasing water hardness. Besides dissolution of carbonates dissolved species such as nitrate, chloride, and sulfate are leached from soil and aquifer rocks together with only small amounts of Mg. Mg not only originates from carbonates but also from Mg–Cl waters are leached from aquifer rocks. Leaching of Mg–Cl brines is particularly high at the beginning of the winter season and lowest at its end. Two zones of recharge are distinguishable. Zone 1 represented by Ein Fara and Ein Qilt is fed directly through the infiltration of meteoric water and surface runoff from the mountains along the eastern mountain slopes with little groundwater residence time and high flow rate. The second zone is near the western border of Jericho at the foothills, which is mainly fed by the under-groundwater flow from the eastern slopes with low surface infiltration rate. This zone shows higher groundwater residence time and slower flow rate than zone 1. Groundwater residence time and the flow rate within the aquifer systems are controlled by the geological structure of the aquifer, the amount of active recharge to the aquifer, and the recharge mechanism. The results of this study may be useful in increasing the efficiency of freshwater exploitation in the region. Some precautions, however, should be taken in future plans of artificial recharge of the aquifers or surface-water harvesting in the Wadi. Because of evaporation and associated groundwater deterioration, the runoff water should be artificially infiltrated in zones of Wadis with high storage capacity of aquifers. Natural infiltration along the Wadis lead to evaporation losses and less quality of groundwater.     

地下水对气候变化的敏感性研究进展

地下水是人类生活、生产、生态用水的重要水源。地下水含水层的补给及其开发利用是水资源可持续开发利用与管理的重要组成部分。浅层地下水的补给主要受制于气候变异与变化。气候变化影响研究从地表水扩展至地下水不仅有利于正确地评估可利用的淡水资源,而且对于改进气候模型,更完整的描写水文循环有重要的科学意义。自21世纪以来,欧美等国开始研究不同时空尺度的地下水补给的定量估算方法,并在气候变化对水资源影响的研究中,考虑了气候变化与人类活动对地下水补给的影响。目前在我国,无论对地下水观测资料的诊断分析,或对地下水补给模型的研制都尚属空白或起步阶段。本文对当前国际上研究地下水补给以及地下水对气候变化敏感性的研究现状予以综述,目的是为了推动我国关于气候变化对水资源影响的深入研究。     

Test methods for characterizing contaminant transport in a glaciated carbonate aquifer

It is widely recognized that karstification can substantially influence flow and transport characteristics in carbonate aquifers. Surface features such as sinkholes are widely used to diagnose the presence of a karst aquifer, but specific borehole tests for karst have not been well defined. Such tests are especially important in glaciated areas where karst features have been eroded or buried by till. One such area is Smithville, Ontario, where more than 60 boreholes at a PCB-contaminated dolostone site provided an opportunity for a wide range of downhole tests and monitoring to be carried out. It was found that there were a number of useful tests for indicating karstification. These included (1) the order of magnitude differences between pump, slug and packer test results, (2) the presence of water table troughs, (3) rapid water level response following recharge events, (4) the rapid changes in water quality following recharge events, (5) water undersaturated with respect to calcite following recharge events, and (6) a wide range in fracture apertures along major bedding planes. Most parameters vary over a similar range at Smithville as they do at Mammoth Cave, Kentucky, indicating that the Smithville aquifer behaves as a typical karst aquifer.