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     

美国Sand Hills地区地下水数值模拟及水量平衡分析

利用地下水数值模型MODFLOW和非饱和带水平衡模型对处于半干旱半湿润沙丘地区(Sand Hills)地下水位进行了模拟,并分析了含水层补排水量,河流与地下水补排关系,以及区域水平衡过程。揭示了独特沙丘地形和土壤特性对地下水补排量的影响。模拟结果表明,入渗率大、非饱和带厚的沙丘有利于降水入渗补给,减少了地下水蒸散发损失。加上下覆含水层具有良好的地下水储水空间,是该地区储存丰富的地下水量,以维持河流稳定流量,供给众多湖泊和湿地的原因。该研究对我国地下水资源评价和生态环境脆弱地区水资源保护具有指导意义。     

哈尔滨市地下水的易污性评价及计算机编图

介绍了目前在国际上采用的地下水的易污性评价方法－DRASTIC评价方法，用与地下水有关的多因子－地下水的埋深，含水层的净补给，岩性，土壤类型，地形，渗流区介质，水力传导系数等7个相关因子对地下水进行评价，并结合GIS地理信息系统对哈尔滨市地下水的易污性进行评价，编制了哈尔滨市地下水的易污图，为今后地下水资源管理，土地利用，城市环境管理者等进一步制定管理方针政策提供了重要的依据。     

Monitoring of wastewater percolation in unsaturated sandy soil using geoelectrical measurements at Gabal el Asfar farm,northeast Cairo,Egypt

The use of wastewater for irrigation in sandy soil increases the pollution risk of the soil and may infiltrate to the shallow groundwater aquifer. In such environment, some important parameters need to be obtained for monitoring the wastewater in the unsaturated zone over the aquifer. These parameters include clay content, heterogeneities of the upper soils, depth to the aquifer and the variations of groundwater quality. In the present work, the efficiency of DC resistivity method in forms of 1-D and 2-D measurements was studied for wastewater monitoring in the Gabal el Asfar farm, northeast of Cairo, Egypt. Forty-one Schlumberger soundings (VES) were performed then followed by three pole-dipole 2-D profiles along some considered regions within the area. The resistivity measurements were integrated with the boreholes, hydrogeological and hydrochemical (surface and groundwater samples) information to draw a clear picture for the subsurface conditions. The obtained results were presented as cross sections and 3-D visualization to trace the clay intercalations within the unsaturated zone. In addition, a vulnerability map was created using the obtained results from 1-D Schlumberger survey and confirmed with the 2-D resistivity profiling. The obtained results have shown that the 2-D resistivity imaging technique is a powerful tool for mapping the small-scale variability within the unsaturated zone and the wastewater infiltration. However, limitations of resistivity techniques were observed in the area with limited resistivity contrast such as thin clay layers with brackish water background. Under that condition, the measured pattern of resistivity distributions depends on the applied electrode array, electrode spacing and using the available geological information during the inversion process.     

基于过程模拟的李官堡水源地地下水污染预警

基于过程模拟的地下水污染预警是基于包气带和饱和带过程模拟的耦合实现的,且融合了涵盖整个地下水系统的四个预警指标。选取浑河冲洪积扇的李官堡水源地为例,基于Hydrus-1D和Visual Modflow分别进行包气带过程模拟和饱和带过程模拟,针对潜层和承压层的复杂程度分别制定了各自的预警临界值;经分析可知,随着时间的推移,地表污染物持续进入到地下水中,污染晕范围不断扩大,地下水中最大浓度值和水源井浓度值也持续增加,且承压含水层的预警级别要高于潜水含水层;同时基于潜层和承压层中污染物最大浓度值与时间分别近似呈线性关系和指数关系可进行长时间尺度的预警;并提出了零级预警区和一级预警区管理措施以监测和预防为主,二级预警区、三级预警区和四级预警区管理措施以控制和监测为主。     

Contribution of geophysical surveys to groundwater modelling of a porous aquifer in semiarid Niger: An overview

Subsurface geophysical surveys were carried out using a large range of methods in an unconfined sandstone aquifer in semiarid south-western Niger for improving both the conceptual model of water flow through the unsaturated zone and the parameterization of numerical a groundwater model of the aquifer. Methods included: electromagnetic mapping, electrical resistivity tomography (ERT), resistivity logging, time domain electromagnetic sounding (TDEM), and magnetic resonance sounding (MRS). Analyses of electrical conductivities, complemented by geochemical measurements, allowed us to identify preferential pathways for infiltration and drainage beneath gullies and alluvial fans. The mean water content estimated by MRS (13%) was used for computing the regional groundwater recharge from long-term change in the water table. The ranges in permeability and water content obtained with MRS allowed a reduction of the degree of freedom of aquifer parameters used in groundwater modelling.     

北京怀柔地区入渗河水空间分布研究

河水入渗路径和范围对确定地下水补给条件,以及水资源调控和合理利用有着重要意义。针对2015年以来怀柔地区地下水水位回升现象,开展了地下水动态影响因素研究,采集了河水和地下水样品,测试了水化学和氢氧稳定同位素组成。δD-δ18 O数据表明该区有河水入渗补给地下水,河流附近地下水为地下水与入渗河水的混合物。利用地下水δ18O值以及二元混合模型计算了地下水中入渗河水的比例,揭示出地下水中河水占比减小方向与地下水水力梯度下降方向一致;局部河段附近地下水Cl-含量增加,表明河水入渗会引起地下水水质变化。入渗河水影响范围的圈定为评价入渗河水对地下水的影响提供了重要数据。该项工作对理解研究区地下水水文过程、控制因素以及水资源管理具有指导意义。     

卫河流域河流地下水流系统氮素运移的数值模拟

卫河是海河流域污染最严重的河流之一,该河如何影响附近浅层地下水的水质是长期受到重视但缺乏定量研究的关键问题。为探讨这一问题,利用Hydrus 2d模型模拟河流非饱和带氮素的迁移转化,以GMS软件中的RT3D模块模拟氮素在饱和含水层中的运移,将包气带底部淋滤出的污染物浓度定为饱和带溶质运移模型的上边界条件,首次实现了河流非饱和带饱和含水层氮素运移的联合模拟,得到河流线状污染源对浅层地下水的影响程度及范围。研究结果表明：由于吸附作用、硝化反硝化作用的存在,从河流上游到下游,包气带厚度加大,运移至含水层中的NH4-N、NO2-N浓度呈下降趋势,而NO3-N浓度则呈上升趋势。随着入渗时间的增长,进入饱和含水层中的NH4-N、NO2-N、NO3-N的浓度逐渐升高并最终保持稳定。污染的河流对浅层地下水的影响呈带状分布,污染物随入渗水流在包气带中垂直入渗;在饱和含水层中以水平运移为主,污染羽偏向地下水流动的方向,其影响距离不超过500 m。     

Regional recharge estimation using multiple methods: an application in the Annapolis Valley, Nova Scotia (Canada)

Recharge is a key parameter in groundwater resources management, and a reliable estimate of recharge is required for their sustainable development. Several methods are available to evaluate recharge; however, selecting the appropriate one is made difficult because each method has its advantages and drawbacks, and results can vary greatly from one method to another. Recharge methods can actually refer to different processes. This paper compares and discusses the results obtained from five regional-scale recharge assessment approaches applied to a fractured rock aquifer in a region with a temperate and humid climate (Annapolis Valley, Nova Scotia, Canada). These methods are distinguished between those providing estimates of the net infiltration (I) into the subsurface (river hydrograph separation and soil moisture balance) from those considering the net recharge (W) to the regional bedrock aquifer (river 7-day low-flows, the corrected soil moisture balance, a numerical groundwater flow model developed with FEFLOW and an infiltration model developed with HELP). The estimated net infiltration ranges from 160 to 250 mm/year, whereas the net recharge estimates range from 80 to 175 mm/year for the entire study area. Although different assessment methods were used, the estimated recharge range is still quite large, demonstrating the importance of using several methods. This case study should provide guidance on choices to be made in the development of a strategy for assessing representative values of aquifer recharge at the regional scale under similar geological and climatic conditions. The use of multiple complementary approaches should lead to a better understanding of the system dynamics and to better defined a representative range of recharge estimates.     

Hydrochemical models of the sulphidic tailings dumps at Matchless (Namibia) and Selebi-Phikwe (Botswana)

The sulphidic tailings dumps at Matchless (Namibia) and Selebi-Phikwe (Botswana) are located in a similar semiarid environment but have a contrasting mineralogical composition. The Matchless tailings are pyrite-rich, whereas the Selebi-Phikwe tailings are dominated by pyrrhotite. Hydrochemical models are established with computer codes for water-balance, sulphide oxidation rate and hydrochemical equilibrium calculations. The data input is based on detailed mineralogical, chemical and kinetic investigations carried out on the core of boreholes drilled in 2000 and 2003. The oxidation of pyrrhotite proceeds at a much faster rate than the oxidation of pyrite. The PYROX code, which is used for kinetic calculations, can take these differences into account by applying different oxide-coating diffusion coefficients (D₂) for pyrrhotite and pyrite. Humidity-cell testing is widely used to predict the post-mining composition of drainage water in humid climates. However, the semiarid conditions at Matchless and Selebi-Phikwe only allow a minimal water flux within the dump. Under such conditions, humidity-cell testing is likely to overestimate the seepage-water pH. This is suggested by the hydrochemical equilibrium calculations for the post-mining period at Selebi-Phikwe, which predict a seepage-water pH about one unit lower than the pH at the end of the 26-weeks humidity-cell testing period. The acidity of the seepage water can be reduced by about half a pH unit, if an oxygen barrier below the evaporation zone is installed. A clay layer 0.5 m thick covered by >1.5 m tailings represents the optimal design for a wet barrier. All three computer codes used for water-balance calculations (HELP3, UNSAT-H and HYDRUS-1D), predict >85% average water saturation for such a layer, which diminishes the diffusion of oxygen into the pile and production of SO₄⁻² and H⁺. The alternative design for a dry barrier consists of a vegetated silt layer 1 m thick on top of the tailings. This barrier does not significantly influence the diffusion of oxygen although it reduces the net infiltration to ≤11 mm/year.     

Impacts of wastewater irrigation in arid and semi arid regions: case of Sidi Abid region,Tunisia

Impacts of irrigation with treated wastewater effluents on soils and groundwater aquifer in the vicinity of Sidi Abid Region (Tunisia) are evaluated. The groundwater aquifer was monitored by several piezometers, where monthly water levels were registered and groundwater salinity was evaluated. This resulted in characterizing the spatial and temporal evolution of the hydrochemical and hydrodynamic properties of the aquifer, showing thereby the impact of artificial recharge. Piezometric maps for pre-recharge and post-recharge situations were developed and a comparison study of both piezometric situations was considered. The piezometric evolution map showed a generalized rise of the piezometric level in the vicinity of the irrigation zone. The extent of recharge was shown to increase with time as the groundwater level increase, which was localized in the vicinity of the irrigation area, reached more extended zones. Several groundwater samples were withdrawn from wells and piezometers and analyzed. Examining the corresponding physical and chemical parameters showed an increase in the concentrations of nutrients (28 mg/l for NO₃ and 3.97 mg/l for NH₄) in the groundwater aquifer below the irrigation zone, which confirms again the infiltration of treated wastewater effluents. The evolution of soil salinity was examined through chemical analysis of soil samples. Electric conductivities of soils were generally shown to be less than 4 mS/cm while the irrigation water has an electric conductivity that may reach 6.63 mS/cm. This might be explained by the phenomenon of dilution and the capacity of soils to evacuate salts downward.     

"三氮"在黄土非饱和带迁移转化原位试验及数值模拟

通过黄土氮肥淋滤原位试验,对"三氮"(NH4 、NO2-、NO3-)在黄土包气带迁移转化过程进行了深入研究和数值模拟.试验结果表明,硝态氮(NO2-和NO3-)在黄土中迁移性较强,可到达地下水面.由于NO2-的毒性,它在土壤和地下水的累积具有巨大的潜在危险性.因此在研究和模拟"三氮"转化过程中,不能把NO2-仅仅看作是"三氮"转化过程的一个中间过程而忽略它在地下环境中的累积效应.模型识别验证结果表明,"三氮"模拟值与实测值吻合程度较好,可以对"三氮"在包气带中迁移转化和积累过程进行模拟和预测.     

岩溶塌陷发育机理模式研究

岩溶塌陷是我国岩溶区常见的地质灾害。目前,关于岩溶塌陷发育机理模式主要以力学分析为主。文章以岩溶塌陷过程为基础,探讨分析岩溶塌陷发育机理模式。依据地下水埋藏条件,土体分为包气带非饱和土体、潜水层饱和土体及承压水层承压性土体。根据“水-+土”相互作用,在包气带、潜水层和承压水层分别建立崩解作用、潜蚀作用和水力裂隙作用三种岩溶塌陷发育机理模式。      

变异条件下内蒙古呼包平原地下水演化趋势

重点探讨气候变异对内蒙古呼包平原地下水资源、地下水流场和动态的影响。在介绍呼包平原水文地质条件的基础上,运用地下水模型软件PMWIN 5.1建立了研究区双层地下水流模型,并根据1998年地下水动态观测和统测资料对模型进行识别。通过对近51 a降水量的分析,确定将连续出现的2个特枯年作为地下水的变异条件,运用地下水模型对变异条件下地下水状态进行模拟,结果表明：2年间对地下水的严重超采,使地下水亏空量达75 296.34 万m³,潜水和承压含水层的地下水位大幅度下降,潜水位最大下降4 m左右,承压水位最大下降17 m左右;漏斗中心主要集中在开采量大的呼和浩特和包头市区。     

Travel time based approach for the assessment of vulnerability of karst groundwater: the Transit Time Method

Karst aquifers represent important water resources in many parts of the world. Unfortunately, karst aquifers are characterised by high contamination risks. This paper presents a travel time based method for the estimation of karst groundwater vulnerability. It considers (1) physics-based lateral flow within the uppermost weathered zone (epikarst) in a limestone-dominated region and (2) high velocities of vertical infiltration at discrete infiltration points (e.g. sinkholes) or lines (e.g. dry valleys, faults). Consequently, the Transit Time Method honours the actual flow path within the unsaturated zone of a karst aquifer system. A test site in Northern Jordan was chosen for the demonstration of the assessment technique, i.e. the catchment area of the Qunayyah Spring north of the capital Amman. The results demonstrate that zones of highest vulnerability lie within valleys and nearby main fault zones. It also reveals that regions, categorised as protected areas by other methods due to thick unsaturated zones, contribute to a major degree to the total risk.     

Groundwater vulnerability map of the Chrzanów karst-fissured Triassic aquifer (Poland)

A map shows intrinsic vulnerability to pollution of the Chrzanów karst-fissured aquifer (273 km²) in the southern part of Poland. This aquifer is intensively drained by numerous intakes and Zn-Pb ore mines. A DRASTIC-type parametric system was applied for groundwater vulnerability evaluation. Vulnerability assessment is based on six factors (depth to groundwater table, lithology of the unsaturated zone, net recharge, hydraulic conductivity of the aquifer, groundwater flow velocity, aquifer thickness). For the final vulnerability map construction at the scale of 1:50,000, a combination of the aquifer simulation model (using MODFLOW) and a geographical information system was applied. Maps of the net recharge, hydraulic conductivity of the aquifer and groundwater flow velocity were derived by aquifer modelling. Based on the vulnerability index (21-182), six relative vulnerability classes were selected. Reliability of the map has been verified.     

The distribution of agricultural soil leachates in the unsaturated zone of the British chalk

In Europe the Chalk constitutes a major source of potable water supply. Its outcrop forms extensive tracts of agricultural land, where the groundwater resources largely originate as infiltrating excess rainfall. Research on the unsaturated zone of the aquifer beneath such cultivated land should allow an assessment of nutrient leaching losses from the associated highly permeable soils and the prediction of future groundwater quality trends. Pore-water profiles for nitrate and numerous other constituents from a site of exceptionally detailed study are presented and compared to results from sites elsewhere in eastern England to demonstrate the impact of modern arable agriculture. Environmental isotopes have also been investigated in depth to aid the study. The problems in evaluating the evolution of the unsaturated zone profiles are discussed. Presented at the International Symposium, International Association of Hydrogeologists, “Impact of Agricultural Activities on Ground Water Quality and Quantity,” Prague, Czechoslovakia, September, 1982.     

Conceptual model of recharge to southeastern Badain Jaran Desert groundwater and lakes from environmental tracers

Sources of groundwater recharge to the Badain Jaran Desert in China have been investigated using geochemical and isotopic techniques. Stable isotope compositions (δ¹⁸O and δ²H) of shallow groundwater and surface water from oasis lakes evolve from a starting composition considerably depleted compared to local unsaturated zone moisture, confirming inferences from chloride mass balance that direct infiltration of precipitation is not a volumetrically important source of recharge to the shallow aquifer in the study area. Shallow phreatic and deeper confined groundwater bodies appear unconnected based on chemical composition and radiocarbon activities. Hydrogeologic evidence points toward a bordering mountain range (Yabulai) as a likely recharge zone, which is consistent with tracer results. A mean residence time in the range of 1–2 ka for the desert’s southeastern margin is inferred from radiocarbon. These results reveal that some replenishment to the desert aquifer is occurring but at a rate much lower than previously suggested, which is relevant for water resources planning in this ecologically sensitive area.     

河北省滦县李家屿灰场2#副坝区灰水运动的水文地质评价

韩家哨村位于河北滦县李家屿灰场北部谷地,地势低于灰场,距离约800m。灰场运行期间,该区地下水出现水位升高及水质变差等问题。本文从水文地质条件角度,详细研究灰水的运移途径及其对该区地下水的影响。韩家哨村区域地下水系统分为上层滞水和孔隙一裂隙（溶隙）潜水含水层系统。潜水含水层系统水力传导系数为172．6～203．4m^2／d。地下水补给主要来源于韩家哨村以南坝后地形较高区域及灰水。灰水渗漏优势区韩家哨村南部宽约200m的带状区域。灰场堆灰形成新的地下水分水岭致使灰水在20副坝坝前垂直下渗进入风化带,沿白云岩裂隙（溶隙）补给潜水含水层,并向韩家哨村区域流动补给孔隙含水层,改变后的潜水部分通过民井向外排泄。     

基于VSF的非饱和-饱和带耦合过程的三维水流数值模拟

包气带作为"四水转化"的关键带,在地下水流与溶质运移模拟中起着重要作用。VSF是一款基于MODFLOW-2000开发的用于模拟非饱和-饱和带水分变化和运移过程的数值模拟程序。本文首先介绍了VSF程序的设计原理与结构,并重点介绍了VSF区别于MODFLOW-2000的用以概化非饱和带水分运移和边界条件设置的子程序包模块,包括Richards方程渗流(REF)、浸润面(SPF)、地表滞水(PND)、地表蒸发(SEV)和植物根区蒸散发(RZE)等子程序包。本文以REF、SPF、PND和SEV等子程序包为例,将VSF与MODFLOW-2000耦合应用于一个非饱和-饱和带水流运移过程的模拟算例。结果表明,VSF可与MODFLOW耦合实现饱和带水位与非饱和带饱和度的同步计算,并能刻画模型中单元格饱和状态的变化过程,其多种实用的边界条件可提供较为全面的模拟条件,是模拟实际包气带-饱和带耦合问题的有效工具。