Numerical simulation of karst groundwater system for discharge prediction and protection design of spring in Fangshan District,Beijing

As the rapid growth of population and social economy, the situation of water resources shortage in Beijing city becomes more and more serious. Karst groundwater in Beijing has great potential for development. The reasonable exploitation of karst groundwater can enhance the water-supply stability of Beijing city. Firstly, the distribution of springs has been investigated in Fangshan, Beijing, and the characteristics of these springs have also been analyzed. Secondly, the hydrogeological conceptual model has been built, based on this, the groundwater flow numerical simulation model was established, and the parameter identification and validation of the model were performed under groundwater level and spring discharge. The results shows that the simulated values of groundwater level and spring discharge are very close to measured values, and the model can be used for groundwater resources evaluation and spring discharge prediction. Finally, a reasonable exploitation design has been developed with three exploitation scenarios considering the spring discharge protection; meanwhile, the quantity of groundwater resources was evaluated in the karst aquifer. The simulation results indicate that different exploitation yields have a significant impact on spring discharge; and the effective measures should be taken to protect the spring discharge     

Surface and subsurface conceptual model of an arid environment with respect to mid- and late Holocene climate changes

The water demand in arid regions is commonly covered by groundwater resources that date back to more humid periods of the Pleistocene and Holocene. Within the investigated arid part of SE Saudi-Arabia information about climate, groundwater levels, and pumping rates are only available for regions where groundwater extractions occur at present-day. For the prediction of the impact of long-term climate changes on groundwater resources an understanding of the hydrogeological and hydrological past and the development of the aquifers is necessary. Therefore, all available information about hydrology and hydrogeology for the past 10,000 years BP were collected and compiled to a conceptual model of the aquifer development on the Arabian Peninsula since the last Ice-Age. The climatic history was displayed by changes in precipitation, temperature and recharge during the mid-S and late Holocene. The hydrogeological development is described by groundwater ages, sea level fluctuations, movement of the coastline, and the development of sabkhas. The most sensitive parameter to describe the development of aquifer system is recharge. Present-day recharge was calculated with the hydrological model system HEC-HMS accounting for current precipitation, temperature, wind, soil types, and geomorphology. With respect to changes in precipitation and temperature over the past 10,000 years the temporal and spatial variability of groundwater recharge was calculated using empirical equations valid for semi-arid and arid settings. Further inflow into the groundwater system results from surface water infiltration in wadi beds, while natural outflow from the groundwater system occurs by discharge to the Gulf, evaporation from sabkhas, and spring discharge. Backward predictions can be verified by sedimentological observations of palaeo-river systems and lakes indicating that groundwater levels reached temporarily the surface under wetter climate conditions and ¹⁴C groundwater ages displaying groundwater residence times.     

利用泉水电导率频率分布辨别岩溶含水系统的水源组分

岩溶含水系统中水源组分的识别能帮助认识系统的结构,解决岩溶水文及水化学研究的基础问题。以灵水岩溶大泉为例,分解了4个水文年的电导率频率分布隐藏的峰,并对其所代表的水源组分进行分析。发现灵水泉口的水源组分主要有4种:① 含水系统中岩溶裂隙或管道中释放的重力水,占53%~77%;② 源于泉口附近携带污染物质的水源,占3%~7%;③ 强降雨期间通过覆盖层分散入渗的水源,或先前存贮在管道或裂隙中流动性差的水被带出含水层,占13%~42%;④ 地面径流以及直接降落到湖面的雨水,占2%~3%。将灵水的电导率频率分布与峰丛洼地的两个典型岩溶水系统对比,分析了电导率的频率分布所蕴藏的含义。研究结果为西南3 620个岩溶水系统的进一步归类提供了参考。     

Tracing groundwater discharge in a High Arctic lake using radon-222

In the High Arctic, groundwater fluxes are limited by the presence of continuous permafrost, although it has been hypothesized that there may be localized groundwater flow and hydraulic connectivity beneath large lakes, due to the presence of taliks, or large regions of unfrozen ground. However, due to the logistical difficulty of employing seepage meters and piezometers in deep, ice-covered lakes, relatively little is known about groundwater discharge to polar lakes. One method of assessing groundwater discharge is through the use of geochemical tracers. We conducted a pilot study to quantify groundwater discharge into a High Arctic lake using dissolved radon gas as a geochemical tracer. Lake water was collected in 15 L polyvinyl chloride (PVC) bags with minimal atmospheric interaction from a 25-m deep lake near Shellabear Point, Melville Island, Northwest Territories, Canada. Sample bags were aerated through a closed water loop for 60 min to allow sufficient radon to equilibrate in a coupled air circuit. Radon in air concentrations were measured on a Durridge RAD7 portable alpha spectrometer. The field trial in a remote setting and separate tests with groundwater samples collected from a temperate site demonstrate the utility of the methodology. The limited results suggest that radon levels in the lower water column are elevated above background levels following nival melt in the surrounding watershed. Although these results are insufficient to quantify groundwater discharge, the results suggest subsurface flow may exist, and further study is warranted.     

遥感技术在新生代水文地质调查中的应用：以喀喇昆仑山温泉幅1∶25万区域水文地质调查为例

以ETM+遥感数据为主要遥感信息源,应用遥感技术对喀喇昆仑山温泉地区进行1∶25万图幅的水文地质调查。根据地质体的影像特征并与前人地质填图结果对比,建立了遥感解译标志。重点对新生代地层及与水文地质有关的要素等进行解译,编制1∶25万新生代遥感解译图。根据遥感图像对研究区的第四纪沉积物的成因类型和分布范围、地貌特征及河流、湖泊、泉群、地下水溢出带、湿地等水文地质特征进行了研究。基于区内地下水形成环境的差异,地下水资源体系可以分为南部河谷冲积层地下水系统和北部内流湖盆地下水系统。总结地下水的分布特征认为,南部冲积层储水条件较为优越,且补给充分,其地下水与地表水构成一个统一的水资源系统;北部内流湖盆地区多为湖相沉积,受气象因素制约,山前巨大的冲洪积扇存在丰富的地下水外,地下水资源总体贫乏。遥感水文地质调查表明,遥感技术在高原区域填图与水文地质调查中具有高效率低成本的优点,可以在青藏高原水文地质调查中发挥重要作用。     

Hydrogeochemistry and isotope techniques to determine water interactions in groundwater-dependent shallow lakes,Wet Pampa Plain,Argentina

This paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater-dependent shallow lakes in the Southeastern Pampa Plain of Argentina. Water samples (lakes, streams, spring water and groundwater) for hydrochemical and stable isotopic determination were collected and the main physical–chemical parameters were measured. The combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin. The hydrochemical processes which explain Los Padres Lake water chemistry are evaporation from groundwater, CO₂ input, calcite dissolution, Na⁺ release by Ca²⁺ and Mg²⁺ exchange, and sulfate reduction. The model that best aligns with La Brava Lake hydrochemical constraints includes: mixing, CO₂ and calcite dissolution, cationic exchange with Na⁺ release and Mg²⁺ adsorption, and to a lesser extent, Ca/Na exchange. This model suggests that the fractured aquifer contribution to this water body is greater than 50 %. An isotopic-specific fingerprint for each lake was identified, finding a higher evaporation rate for La Brava Lake compared to Los Padres Lake. Isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability. The Tandilia Range System, considered in many hydrogeological studies as the impermeable bedrock of the Pampean aquifer, acts as a fissured aquifer in this area, contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition.     

西北某干旱区多级储水洼地地下水数值模拟

西北某放射性废物处置场预选区,区域地下水系统包含多级独立第四系储水洼地,洼地出口以泉水排泄地下水,继而回渗补给下级洼地。根据含水层底板起伏特征,利用GMS模拟软件中的排水沟模块与溪流模块概化了泉水,通过泉流量校准与监测孔水位拟合,校正了研究区渗透系数、给水度、和储水率等水文地质参数,计算了地下水流速、流向以及地下水资源量。结果显示,研究区地下水由南向北东径流,东北部为最终排泄洼地,地下水流速缓慢,水资源相对匮乏,有利于放射性废物处置的安全。     

Investigation of discharge-area groundwaters for recharge source characterization on different scales: the case of Jinan in northern China

Discharge-area groundwater in Jinan, a typical karst region in northern China, was investigated by studying both the hydrological and chemical processes evolving from the recharge in mountainous terrains to the karst-spring outflows in the metropolitan area. Large-scale exploitation of karst groundwater has led to a disturbing trend in the ever-decreasing spring outflow rates and groundwater level. There is insufficient information about the Jinan karst aquifers, which provide the main water sources to meet human demand and to sustain spring outflow. The coupling of hydrological and chemical processes quantifies the flow system through aqueous chemistry characterization of the water sources. This approach is used to study the groundwater flow discharges in different locations and geological settings. The potentiometric data indicated limited vertical connectivity between distinct hydrogeological units and alteration of the recharge regime by the faults and by artificial exploitation. Shallow groundwater primarily belongs to the local flow system, with high nitrate concentration and enriched stable isotopic contents. Thermal groundwater has high concentrations of chloride and total dissolved solids, derived from a regional flow system with the highest recharge altitudes and long residence time. Non-thermal karst water may be attributed to the intermediate flow system, with uniform HCO₃–Ca(Mg) facies and low nitrate concentration. This work highlighted discharge as a fingerprint of groundwater flow conditions and provides a better insight into the hydrogeological system.     

西南某岩溶区地下水系统示踪试验与解析

以西南某典型岩溶区为例,解析示踪试验在岩溶管道连通性以及获取水文地质参数中的应用。选择落水洞为投放点,分别从落水洞西侧和东侧寻找地下水出露点作为接收点,判别落水洞地下径流的实际去向以及落水洞与接收点之间的水力联系。结合Qtracer2软件对示踪试验成果进行定量解析,确定示踪剂回收率、地下水平均流速、最快流速,估算出岩溶管道结构特征和水文地质参数。结果表明:落水洞与接收点JS01、JS03之间不存在直接水力联系;落水洞与接收点JS02存在水力联系且岩溶管道极为发育,含水介质不均匀,地下水运移路径较为通畅,为典型的紊流流态;落水洞地下径流的主要方向是由西向东,但在丰水期雨量较大期间,接收点JS04能够接收到荧光素钠,说明丰水期水位上涨后两者间会有水力联系,导致部分水量向落水洞西侧排泄。     

Hydrogeological investigation of groundwater artificial recharge by treated wastewater in semi-arid regions: Korba aquifer (Cap-Bon Tunisia)

Korba aquifer is one of the most typical examples of overexploited coastal aquifer in the Mediterranean countries. In fact, from 1985, a considerable piezometric level drop, water salinization, and seawater intrusion were registered in the aquifer. In December 2008, Tunisian authorities initiated a general plan to groundwater management in order to augment groundwater resources, restore the piezometric levels, and improve water quality. The plan consists of artificial recharge of groundwater used treated wastewater through three infiltration basins. During the first 4 years (from December 2008 to December 2012), 1.41 Mm³ of treated wastewater was injected to the Korba aquifer. This study presents a hydrogeological assessment of groundwater evolution during the recharge processes. In this study, 32 piezometric and chemical surveys of 70 piezometers and observed wells are used to present hydrogeological investigation and water quality evolution of wastewater reuse through artificial recharge in Korba coastal aquifer. The piezometric evolution maps are used to specify the positive effect in groundwater level that exceeding 1.5 m in some regions. The interpretation of salinity evolution maps are used to indicate the improving of groundwater quality.     

A multi-method approach for groundwater resource assessment in coastal carbonate (karst) aquifers: the case study of Sierra Almijara (southern Spain)

Understanding the transference of water resources within hydrogeological systems, particularly in coastal aquifers, in which groundwater discharge may occur through multiple pathways (through springs, into rivers and streams, towards the sea, etc.), is crucial for sustainable groundwater use. This research aims to demonstrate the usefulness of the application of conventional recharge assessment methods coupled to isotopic techniques for accurately quantifying the hydrogeological balance and submarine groundwater discharge (SGD) from coastal carbonate aquifers. Sierra Almijara (Southern Spain), a carbonate aquifer formed of Triassic marbles, is considered as representative of Mediterranean coastal karst formations. The use of a multi-method approach has permitted the computation of a wide range of groundwater infiltration rates (17–60%) by means of direct application of hydrometeorological methods (Thornthwaite and Kessler) and spatially distributed information (modified APLIS method). A spatially weighted recharge rate of 42% results from the most coherent information on physiographic and hydrogeological characteristics of the studied system. Natural aquifer discharge and groundwater abstraction have been volumetrically quantified, based on flow and water-level data, while the relevance of SGD was estimated from the spatial analysis of salinity, ²²²Rn and the short-lived radium isotope ²²⁴Ra in coastal seawater. The total mean aquifer discharge (44.9–45.9 hm³ year^?1) is in agreement with the average recharged groundwater (44.7 hm³ year^?1), given that the system is volumetrically equilibrated during the study period. Besides the groundwater resources assessment, the methodological aspects of this research may be interesting for groundwater management and protection strategies in coastal areas, particularly karst environments.     

Towards a better understanding of the Oulmes hydrogeological system (Mid-Atlas,Morocco)

Located in the Mid-Atlas (Morocco), the Oulmes plateau is famous for its mineral water springs “Sidi Ali” and “Lalla Haya” commercialised by the company “Les Eaux minérales d’Oulmès S.A”. Additionally, groundwater of the Oulmes plateau is intensively exploited for irrigation. The objective of this study, essentially performed from data collected during isotopic (summer 2004) and piezometric and hydrogeochemical field campaigns (spring 2007), is to improve the understanding of the Oulmes hydrogeological system. Analyses and interpretation of these data lead to the statement that this system is constituted by a main deep aquifer of large extension and by minor aquifers in a perched position. However, these aquifers interact enough to be in total equilibrium during the cold and wet period. As highlighted by isotopes, the origin of groundwater is mainly infiltration water except a small part of old groundwater with dissolved gas rising up from the granite through the schists.     

山西辛安岩溶泉形成条件及随机模型

本文详细分析了山西辛安岩溶泉的水文地质条件,并通过对泉域岩溶水的补给、径流、排泄条件的分析,将辛安泉域概化为单输入单输出线性时不变集中参数随机系统的概念模型。利用24年的水文序列资料进行基流分割,获得泉多年月平均流量过程曲线,求得泉年平均流量和年平均补给量。在此基础上,应用滑动平均模型（MA）,自回归—滑动平均模型（AR-MA）及泉流量调和分析—残差自回归等三个模型,对泉域地下水进行模拟,获得了满意的结果,不仅揭示了泉水动态特征,而且对泉流量动态进行了预报,为晋东南区域经济规划提供了有益资料。     

Physicochemical simulation of the evolution of small lakes in a cold climate

The paper presents a generalized algorithm for the simulation of multiyear cycles in variations of the chemical composition of lake waters with regard for the seasonal specifics of hydrogeochemical processes. Data were obtained on the behavior of the hydrogeological system during a time span of 500–1000 years. Each of the simulated model cycles involved a successively alternating “summer-winter” time periods. Terrestrial exchange fluxes between reservoirs, groundwater inflow, falls of atmospheric precipitate, and the evaporation of lake water were taken into account for summer periods, whereas winter conditions were simulated as corresponding to the development of the ice phase, the absence of water exchange fluxes, a change from oxidizing to reducing conditions, and the burial of solid phases in the sediments. The results of our physicochemical simulations with the use of data on the composition of natural hydrogeological systems are in good agreement with natural observations and make it possible to realistically predict the evolution of small lakes in the Ol’khon area.     

Functioning of a karst aquifer from S Spain under highly variable climate conditions,deduced from hydrochemical records

Over a period of three hydrological years during which precipitation was highly variable, measurements of discharge, electrical conductivity, temperature and chemical components of the water at the Cañamero spring (southern Spain) were taken in order to characterise the hydrogeological functioning of the karst aquifer that it drains. The results obtained from analysis of the frequency distribution of electrical conductivity data revealed histograms with a plurimodal morphology (up to 5 modes) and a range of variation that increased with greater pluviometry during the study period. The discharge from this spring increased sharply a few days after major rainfall episodes and, when the discharge reached a value of approximately 3.73 m³/s, an overflow spring started to function. During high-water periods, there were sudden and large falls in EC, temperature and all the chemical components dissolved in the water. This high variability reflects the predominance of groundwater flow through karst drains, a typical feature of conduit flow systems. The considerable hydrochemical heterogeneity observed is caused by the mobilisation of important volumes of recharge waters from shallow areas of the aquifer (soil, epikarst) towards the discharge point, with greater participation of the unsaturated zone during high-water conditions, and a more active role played by the saturated zone during low-water conditions. In karst systems such as the one drained by the Cañamero spring, it is important to monitor several responses (hydrodynamic, hydrothermal, hydrochemical, etc.), with an appropriate sampling frequency and under different hydrometeorological conditions, in order to achieve an adequate hydrological characterisation. This is fundamental for planning, management and protection of groundwater in karst aquifers.     

Climate and irrigation scenario analyses using three-dimensional numerical modelling: a case study of the Nasia sub-basin in the White Volta Basin,Ghana

A groundwater resource characterisation and assessment model was developed for Nasia river sub-basin in the White Volta Basin, Ghana. The model is useful to policymakers for planning and sustainable management of groundwater resources in the basin for domestic and irrigation purposes. A conceptual model was constructed that characterized boundary conditions and hydrostratigraphy, and estimated recharge rates and hydraulic and storage parameters. From current understanding of the hydrogeological dynamics, three hydrostratigraphic layers were delineated. The conceptual model was converted to a three-dimensional steady-state groundwater flow model using MODFLOW. Recharge rates estimated from the base model indicate a minimum of 1.1% and maximum of 6.2% of the total rainfall. The hydraulic conductivity ranged between 0.20 and 15 m/day. Four possible scenarios were simulated: (1) increased population, (2) climate variations (reduced recharge), (3) increased abstraction for irrigation, and (4) worst-case scenario which is a combination of the first three scenarios. Results from scenarios 1 and 2 indicated that, under such conditions, the groundwater resources could be sustained and no significant effect on any of the water budget indicators was observed. For scenario 3, there was significant drop in hydraulic head in the central portions of the study area. The scenario 4 simulation indicated that there was significant reduction in groundwater levels and groundwater discharge into streams under these stressors. Such reduction can affect stream levels in the basin and, subsequently, the ecosystem. These findings are valid within the limits of uncertainty in the hydrogeological data that were used in this study.

     

人类活动影响下娘子关岩溶水系统地球化学演化

娘子关泉是我国北方最大的岩溶泉之一,也是阳泉市工农业生产和人民生活的重要供水水源。地下水地球化学演化分析表明,在地下水由补给区向排泄区运移过程中,除固有的水岩相互作用外,由于受采矿活动和地表水入渗补给的影响,岩溶水由低离子含量的HCO3-SO4或HCO3型水逐渐成为SO4型、SO4-HCO3型和SO4-HCO3-Cl型水。在泉群集中排泄区,区域流动系统与局部流动系统的地下水发生混合作用,最终形成了水质相对良好的HCO3-SO4型或SO4-HCO3型岩溶泉水。在此过程中,地下水对方解石和白云石也由最初的溶解作用演变为沉淀再结晶。尽管石膏呈持续溶解现象,但在采煤活动严重影响区域,石膏的沉淀也可能出现。地球化学模拟表明,在岩溶含水层中,地下水首先以方解石（白云石）的溶解为主;随着石膏溶解数量的增加,方解石（白云石）的溶解开始受到抑制,进而发生沉淀,石膏的溶解成为控制地下水水化学的主导过程。当矿坑水混入时,地下水相对石膏过饱和,地下水对碳酸盐岩含水介质的溶蚀能力得到增强。随着水岩反应的演进,铁氢氧化物大量沉淀,通过共沉淀和吸附作用去除了地下水中的重金属类污染物。      

泉域地下水数值模拟及泉流量动态变化预测

本文对位于岩溶地区的小南海泉泉域地下水进行了数值模拟和水平衡分析，全面分析了降雨、河、渠、库地表水系入渗对地下水动态变化的影响，模拟了泉流量动态变化与区域地下水关系。在此基础上，分析了不同气候条件和开采方案对泉流量的影响。模型计算结果表明，小南海泉流量多年平均相对变化率与降雨量多年平均变化率基本一致，减少泉域地下水开采量，特别是矿坑排水可有效地增加枯期泉流量。     

应用环境示踪剂探讨巴丹吉林沙漠及古日乃绿洲地下水补给

巴丹吉林沙漠位于我国西北部的阿拉善高原。近年来,许多中外学者应用天然水样及土壤水分的水化学、同位素等技术手段研究了该地区地下水补给及环境演化。基于这些研究,试图给出巴丹吉林沙漠和古日乃绿洲一个完整的二维地下水系统概念模型。巴丹吉林沙漠地下水在浅埋区和出露区蒸发,同时接受少量当地降水补给,其最终的排泄区是古日乃绿洲。巴丹吉林沙漠地下水垂向补给微弱,地下水很可能是更新世晚期至全新世早期周边的雅布赖山区降水径流及发源于祁连山的河流古河道补给的古水。在全新世中-晚期,地下水得到有限的降水补给,并且经受蒸发作用。随着千年尺度的气候转型,两千年以来,巴丹吉林沙漠干旱化加剧,正在经历地下水位下降、湖泊绿洲逐渐萎缩消亡的过程。     

Stable isotope (2H, 18O and 87Sr/86Sr) and hydrochemistry monitoring for groundwater hydrodynamics analysis in a karst aquifer (Gran Sasso,Central Italy)

This paper deals with chemical and isotope analyses of 21 springs, which were monitored 3 times in the course of 2001; the monitoring program was focused on the groundwater of the Gran Sasso carbonate karst aquifer (Central Italy), typical of the mountainous Mediterranean area.Based on the hydrogeological setting of the study area, 6 groups of springs with different groundwater circulation patterns were distinguished. The hydrogeochemistry of their main components provided additional information about groundwater flowpaths, confirming the proposed classification. The spatial distribution of their ion concentrations validated the assumptions underlying the hydrogeological conceptual model, showing diverging groundwater flowpaths from the core to the boundaries of the aquifer. Geochemical modelling and saturation index computation elucidated water–carbonate rock interaction, contribution by alluvial aquifers at the karst aquifer boundaries, as well as impacts of human activities.The analysis of ¹⁸O/¹⁶O and ²H/H values and their spatial distribution in the aquifer substantiated the hydrogeology-based classification of 6 groups of springs, making it possible to trace back groundwater recharge areas based on mean isotope elevations; the latter were calculated by using two rain monitoring stations. ⁸⁷Sr/⁸⁶Sr analyses showed seasonal changes in many springs: in winter–spring, the changes are due to inflow of new recharge water, infiltrating into younger rocks and thus increasing ⁸⁷Sr/⁸⁶Sr values; in summer–autumn, when there is no recharge and spring discharge declines, changes are due to base flow groundwater circulating in more ancient rocks, with a subsequent drop in ⁸⁷Sr/⁸⁶Sr values.The results of this study stress the contribution that spatio-temporal isotope monitoring can give to the definition of groundwater flowpaths and hydrodynamics in fissured and karst aquifers, taking into account their hydrogeological and hydrogeochemical setting.