Hydrogeological mapping as a basis for establishing site-specific groundwater protection zones in Denmark

The water supply in Denmark is based on high-quality groundwater, thus obviating the need for complex and expensive purification. Contamination from urban development and agricultural sources, however, increasingly threatens the groundwater resource. In 1995 the Danish Government thus launched a 10-point plan to improve groundwater protection. In 1998 this was followed by a decision to instigate spatially dense hydrogeological mapping of the groundwater resource within the 37% of Denmark designated as particularly valuable water-abstraction areas. The maps will be used to establish site-specific groundwater protection zones and associated regulation of land use to prevent groundwater contamination. Traditional mapping based solely on borehole data is too inaccurate for this purpose. The work will take 10 years and cost an estimated DKK 920 million, equivalent to 120 million euro (€). To fund this, consumers will pay a € 0.02 surcharge per m³ of drinking water during the 10-year period. This review of the Danish strategy to protect the groundwater resource demonstrates why dense mapping with newly developed geophysical measurement methods in large contiguous areas accords geophysics a highly central role in the forthcoming hydrogeological mapping. It is illustrated by examples of spatially dense, large-scale geophysical mapping carried out in the Aarhus area.

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Resumen El abastecimiento de agua en Dinamarca está basado en agua subterránea de alta calidad, evitando de esta manera la necesidad de una purificación compleja y cara. Sin embargo, la contaminación a través del desarrollo urbano y de fuentes agrícolas, ha incrementado la amenaza para el recurso de agua subterránea. Entonces en 1995 el gobierno lanzó un plan de 10 puntos para mejorar la protección del agua subterránea. Este fue seguido en 1998 por la decisión para promover una cartografía hidrogeológica espacialmente detallada, para el recurso agua subterránea dentro del 37% de las áreas de extracción consideradas por Dinamarca con una importancia especial. Los mapas serán usados para establecer zonas específicas de protección para puntos de agua subterránea y una regulación asociada al uso del territorio, para prevenir la contaminación del agua subterránea. La cartografía tradicional basada exclusivamente en datos de la perforación es muy inexacta para este propósito. Este trabajo tomará 10 años y costará aproximadamente DKK 920 millones, equivalentes a 120 millones de Euros (€). Para financiar esto los consumidores pagarán un sobreprecio de € 0.02 por m³ de agua potable durante un periodo de 10 años. Este análisis de la estrategia Danesa para proteger el recurso agua subterránea, demuestra porque la cartografía detallada, hecha con nuevos avances en métodos de medición geofísica, aplicados a grandes áreas aledañas, otorgan a la geofísica un papel altamente importante en el futuro de la cartografía hidrogeológica. Esto está ilustrado con ejemplos de cartografía geofísica a gran escala y espacialmente detallada, llevados a cabo en el área de Aarhus.

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Résumé Lalimentation en eau au Danemark suppose une haute qualité des eaux souterraines, en éliminant ainsi le coûteux processus dépuration. Néanmoins, la qualité des sources souterraines est menacée par la pollution provoquée par le développement urbain et agricole. En 1995 le gouvernement danois a lancé un plan en 10 points pour améliorer la protection des eaux souterraines. En 1999 ce plan a été suivi par la décision de promouvoir une cartographie hydrogéologique à grande densité sur 37% du territoire du Danemark où se trouvent des zones de captages importantes. Les cartes seront utilisées pour établir les zones de protection des eaux souterraines, en tenant compte des conditions locales du site ainsi que des règlements conjoints dutilisation des territoires, afin de prévenir la pollution des eaux souterraines. La cartographie traditionnelle, basée seulement sur les données des forages, est trop imprécise pour ce but. Les travaux vont durer 10 ans avec un coût estimé à 120 millions deuros (€). Pour ces travaux les consommateurs vont payer une surcharge de € 0.02 par m³ deau potable, ceci pendant 10 ans. Cette révision de la stratégie du Danemark concernant la protection des ressources en eaux souterraines a démontré les raisons pour lesquelles on a accordé un rôle central aux nouvelles méthodes géophysiques dans la future cartographie hydrogéologique de vaste régions. On présente un exemple de cartographie géophysique réalisée dans la région dAarhus.

     

Geophysical methods application in groundwater natural protection against pollution

Natural protection against groundwater pollution mostly depends on water-bearing bed coverage with permeable rocks presenting a good or bad pollution intrusion barrier between the surface and subterranean water. Additional positive effects of polluted groundwater self-purification in these zones are visible. Natural protection from surface pollutants primarily depends on natural (geological) factors: (1) presence of poorly permeable rocks; (2) depth, lithology (grain-size distribution), and filtration features of rocks covering groundwater reservoirs; and (3) aquifer depth. In contrast to artesian aquifers, quantitative and qualitative evaluation for natural protection of intergranular aquifers with a free water surface is significantly complicated. In this case, the estimation is possible with the help of a specially developed statistical method, which requires the following elements referring to the zone of aeration: (1) poorly permeable strata depth; (2) filtration features; (3) groundwater level depth; and (4) lithology. For quantitative evaluation, it is necessary to know the time interval for pollution propagating from surface of the terrain to the free water surface. Describe access is particularly useful in the domain of zones of sanitary protection defined around the source of groundwater. This exploration method could be considerably rationalized by geophysical methods application. Various methods are useful, namely: electric mapping and sounding, self-potential method, seismic reflection and refraction methods, gravity and geomagnetic methods, the turam method, and different well-logging measurements (gamma ray, gammagamma, radioactivity log, and thermal log). In the paper, geophysical methods applictations in natural protection against groundwater pollution and appropriate critical analysis are presented. The results of this paper are based on the experience and application of geophysical methods to groundwater studies in Yugoslavia by the author.     

Integrated methods and scenario development for urban groundwater management and protection during tunnel road construction: a case study of urban hydrogeology in the city of Basel,Switzerland

In the northwestern area of Basel, Switzerland, a tunnel highway connects the French highway A35 (Mulhouse–Basel) with the Swiss A2 (Basel–Gotthard–Milano). The subsurface highway construction was associated with significant impacts on the urban groundwater system. Parts of this area were formerly contaminated by industrial wastes, and groundwater resources are extensively used by industry. During some construction phases, considerable groundwater drawdown was necessary, leading to major changes in the groundwater flow regime. Sufficient groundwater supply for industrial users and possible groundwater pollution due to interactions with contaminated areas had to be taken into account. A groundwater management system is presented, comprising extensive groundwater monitoring, high-resolution numerical groundwater modeling, and the development and evaluation of different scenarios. This integrated approach facilitated the evaluation of the sum of impacts, and their interaction in time and space with changing hydrological boundary conditions. For all project phases, changes of the groundwater system had to be evaluated in terms of the various goals and requirements. Although the results of this study are case-specific, the overall conceptual approach and methodologies applied may be directly transferred to other urban areas.     

Karst groundwater management by defining protection zones based on regional geological structures and groundwater flow fields

In a semiarid region, the karst aquifer generally forms a large groundwater reservoir that can play an important role in regional water supply. But because of the specific physical properties of karst aquifers, they are vulnerable to pollution and anthropogenic impacts. Karst groundwater management strategies are vital. As representative of karst springs in a semiarid area, Niangziguan Springs is located in the east of Shanxi Province, China with an annual average rate of discharge of 10.34 m³/s (1956–2003) (Y. Liang, unpublished data). The Niangziguan Spring Basin covers an area of 7,394 km² with an annual average precipitation of 535 mm (1958–2003) (Hao et al. in Carsologica Sinica 23(1):43–47, 2004). Over the past three decades, accelerated groundwater exploitation has caused water-table decline in the aquifer, reduction of the spring discharge, and deterioration of water quality. In this study, three protection zones were defined to ensure the quality and capacity of this resource. The confluence of the 11 spring systems and the discharge areas were defined as I protection zone, the recharge basin was II protection zone, and the slack water area where there is little surface recharge was the III protection zone. Management strategies for each zone were suggested and evaluated to provide a scientific foundation for sustainable utilization.     

The evolution of groundwater rights and groundwater management in New Mexico and the western United States

Historically, rights in water originated as public property and only later became individualized rights to utilize the public resource, in a manner consistent with the public welfare needs of society, but protected by principles of property law. Five basic regulatory systems for rights in groundwater in the United States have evolved to date. The problems raised by the hydrologic differences between groundwater hydraulically connected to stream systems and groundwater in non-replenished aquifers have been resolved to some extent by a couple of leading court cases. Numerical modeling and other technical methodologies have also evolved to evaluate the scientific issues raised by the different hydrologic conditions, but these are not immune from criticism. The current role of aquifers is evolving into that of storage facilities for recycled water, and their utilization in this manner may be expanded even further in the future. The policy implications of the choices relating to joint management of ground and surface water cannot be overstated. As this paper demonstrates, proactive administration of future groundwater depletions that affect stream systems is essential to the ultimate ability to plan for exploitation, management and utilization of water resources in a rational way that coordinates present and future demand with the reality of scarcity of supply. The examples utilized in this paper demonstrate the need for capacity building, not just to develop good measurement techniques, or to train talented lawyers and judges to write good laws, but also for practical professional water managers to keep the process on a rational course, avoiding limitless exploitation of the resource as well as conservative protectionism that forever precludes its use.

Modeling the impact of groundwater harvesting on the hydro-salinity of a saline catchment in southeastern Australia

Recharge to a saline, unconfined shallow-water-table aquifer is normally considered as an irrecoverable loss of water, but such thinking could be reviewed empirically. The use of an appropriate groundwater harvesting system does not only provide an opportunity to recover this lost water, but can also help in catchment salinity management and improvement. Agricultural-based land-drainage systems such as those that use serial biological concentration (SBC) of salts, provide examples of such harvesting methods. The impact of groundwater harvesting has been assessed on the hydro-salinity of a saline catchment in southeastern Australia through modeling. For both the below average rainfall and very wet years, the “do nothing” scenario resulted in increasing salinization in the catchment. However, after introducing a SBC system, groundwater salinity showed a decreasing trend while hydraulic heads tended to stabilize around the depth of subsurface collector wells. However, for a successful groundwater harvesting system, proper understanding of the groundwater flows and salt mobilization associated with a catchment is necessary. The outcomes of this modelling study have the potential to address similar issues (salinization) and/or needs (water harvesting) existing elsewhere in the world, particularly in semi-arid regions.

The protection of groundwater dependent ecosystems in Otago, New Zealand

Surface waters (streams, rivers, and wetlands) are the most important groundwater dependent ecosystems (GDEs) in Otago, New Zealand. Pumping wells in the vicinity can deplete water in the GDE. In Otago, most of the surface water resources are allocated and a method, which would assist in the implementation of water management policy, is needed to acknowledge the strong hydraulic link between surface and shallow groundwater. A simplified method has been developed which derives a numerical relationship between the bore pumping rate and the distance between the bore and surface water body beyond which depletion is considered insignificant. A range of GDE depletion scenarios are examined at various combinations of hydraulic parameters to find a minimum distance for a given pumping rate, at which 90% of the modelled surface water depletion scenarios become less than a threshold GDE depletion after a specified time. A buffer zone, based on the minimum distance is placed around GDEs, and groundwater abstraction rights within the buffer are subject to stricter rules. Applicants wishing to abstract from bores within the buffer zone will need to address the environmental impact of the proposed activity on the GDE.     

地下水水位管理研究进展综述

地下水位变化是地下水资源量多寡最直接的表现形式,是地下水管理最重要的控制性指标。对地下水水位进行管理,可实现对地下水资源的量化管理。通过对地下水位与生态及地质环境的关系、地下水位阈值、地下水管理水位划定等几个方面进行综述,力图从相对全面的角度认识当前地下水水位管理的发展。在回顾地下水水位管理以上研究进展的基础上,对我国地下水水位管理面临的问题、地下水管理策略、复合型地区地下水水位管理等发展趋势进行了探讨,为相关研究人员提供一定的参考。     

Analysis of effect of water construction in different phases on groundwater environment

This paper analyses the effect of some water construction in different phases on groundwater environment from several aspects, puts forward reasonable evaluation of groundwater development, and at the same time lists the problems that may arise in environmental hydrogeology. The above analysis and recommendations will have certain reference function to the reasonable development and utilization of groundwater in water construction.     

浅谈太湖流域饮用水安全与地下水保护

太湖流域经济发达,人口稠密,如管理不善将引发水污染严重、水环境恶化和水质型缺水等水问题,对饮用水安全构成威胁。因此,地下水在保障太湖流域饮用水安全中的作用就显得特别重要,提出了太湖流域地下水保护的对策措施。     

Sustainability analysis of groundwater resources in a coastal aquifer, Alabama

Fort Morgan Peninsula is an attached portion of a dynamic barrier complex in the northern Gulf of Mexico and is a large tourist area that brings in a significant amount of revenue for Alabama. Many of the hotels and tourist attractions depend on the groundwater as their water supply. The over-withdrawal of groundwater and saltwater intrustion will have a negative impact on the ecology, tourism and economy if groundwater resources are not properly monitored and managed. In this study a calibrated groundwater flow model was used to analyze the sustainability of groundwater resources at Fort Morgan Peninsula. Detailed flow budgets were prepared to check the various components of inflow and outflow under different water use and climatic conditions. The results indicated the locations where groundwater was over-pumped and subjected to saltwater intrusion, or will be subjected to saltwater intrusion under a range of projected water use and climatic conditions.     

Analysis of travel time,sources of water and well protection zones with groundwater models

This study compares numerical models with analytical solutions in computing travel times and radius of protection zones for a pumping well located in an unconfined aquifer with uniform recharge and in a semi-confined aquifer. Numerical models were capable of delineating protection zones using particle tracking method in both cases. However, protection zones defined by travel time criterion can only protect small percent of source water to the well; large percent of source water is not protected which may pose a risk of pollution of source water to the well. The case study of Leggeloo well field in the Netherlands indicates that although a well field protection area was enforced in 1980s, elevated nitrate concentration has been monitored in the abstracted water since 1990s. The analysis of protection areas shows that the current protection area only protects 37.4% of recharge water to the well field. A large protection area must be adopted in order to safeguard the sustainable water supply for the local community     

Karst groundwater: a challenge for new resources

Karst aquifers have complex and original characteristics which make them very different from other aquifers: high heterogeneity created and organised by groundwater flow; large voids, high flow velocities up to several hundreds of m/h, high flow rate springs up to some tens of m³/s. Different conceptual models, known from the literature, attempt to take into account all these particularities. The study methods used in classical hydrogeology—bore hole, pumping test and distributed models—are generally invalid and unsuccessful in karst aquifers, because the results cannot be extended to the whole aquifer nor to some parts, as is done in non-karst aquifers. Presently, karst hydrogeologists use a specific investigation methodology (described here), which is comparable to that used in surface hydrology.Important points remain unsolved. Some of them are related to fundamental aspects such as the void structure – only a conduit network, or a conduit network plus a porous matrix –, the functioning – threshold effects and non-linearities –, the modeling of the functioning – double or triple porosity, or viscous flow in conduits – and of karst genesis. Some other points deal with practical aspects, such as the assessment of aquifer storage capacity or vulnerability, or the prediction of the location of highly productive zones.

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Resumen Los acuíferos kársticos tienen características originales y complejas que los hacen muy diferentes de otros acuíferos: alta heterogeneidad creada y organizada por el flujo de agua subterránea, espacios grandes, velocidades altas de flujo de hasta varios cientos de m/h, manantiales con ritmo alto de flujo de hasta algunas decenas de m3/s. Diferentes modelos conceptuales que se conocen en la literatura tratan de tomar en cuenta todas estas particularidades. Los métodos de estudio usados en hidrogeología clásica- pozos, pruebas de bombeo y modelos distribuidos- son generalmente inválidos y no exitosos en acuíferos kársticos, debido a que los resultados no pueden extenderse a todo el acuífero ni a alguna de sus partes, como se hace en acuíferos no kársticos. Actualmente los hidrogeólogos kársticos usan una metodología de investigación específica, que se des cribe aquí, la cual es comparable con la que se utiliza en hidrología superficial. Puntos importantes permanecen sin resolverse. Algunos de ellos se relacionan con aspectos fundamentales tal como la estructura de espacios- solo una red de conductos, o una red de conductos más una matriz porosa-, el funcionamiento-efectos threshold y no-linealidades-, el modelizado del funcionamiento-porosidad doble o triple, o flujo viscoso en conductos- y génesis del karst. Algunos otros puntos se relacionan con aspectos prácticos, tal como la evaluación de la capacidad de almacenamiento del acuífero o la vulnerabilidad, o la predicción de la localización de zonas altamente productivas.

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Résumé Les aquifères karstiques présentent des caractères originaux complexes qui les distinguent profondément de tous les autres milieux aquifères : forte hétérogénéité créée et organisée par les écoulements souterrains eux-mêmes, vides de très grandes dimensions, vitesses découlement pouvant atteindre quelques centaines de mètres par heure, sources à débit pouvant atteindre quelques dizaines de m³/s. Différents modèles conceptuels tentent de prendre en compte ces particularités. Les méthodes détude de lhydrogéologie classique—forage, essai de pompage et modèles maillés – ne sont en général pas adaptés aux aquifères karstiques, parce que les résultats obtenus ne peuvent pas être étendus à laquifère tout entier, ou à certaines de ses parties, comme cela est fait pour les aquifères non karstiques. Actuellement les hydrogéologues du karst ont recours à une méthodologie détude spécifique décrite ici, comparable à celle utilisée en hydrologie de surface.Des points importants restent à résoudre. Certains concernent des aspects fondamentaux, comme la structure des vides – réseau de conduits uniquement, ou bien réseau de conduits et matrice poreuse –, le fonctionnement – problèmes de seuil et plus généralement les non-linéarités –, la modélisation du fonctionnement – double porosité ou écoulement visqueux en conduits – et de la genèse du karst. Dautres points portent sur des aspects pratiques, comme lévaluation de la capacité de stockage ou de la vulnérabilité de laquifère, et la prédiction des zones à haute productivité.

     

Ecological function zoning and protection of groundwater in Asia

The natural groundwater recharge in Asia is estimated to be 4 677.74×10⁹ m³/a. However, it features extremely uneven spatial-temporal distribution. Groundwater is distributed in various natural and geological environments, and it is liable to be affected by numerous factors and possesses different properties. Moreover, groundwater faces complex ecological problems. This paper gains a complete understanding of groundwater in Asia in terms of the structure of aquifer systems, the processes of groundwater cycle, and the spatial variation laws of surface ecosystems. Based on this, it proposes the ecological function zoning scheme of groundwater in Asia, aiming to provide guidance for the utilization of regional water resources and the planning for economic and social development, coordinate the relationship between social and economic development and water resource protection, and improve the ecological functions of groundwater. Furthermore, this paper analyzes the problems with regional groundwater management in Asia and puts forward countermeasures and suggestions, thus providing a theoretical basis for the sustainable development and utilization of regional groundwater and environmental protection.     

Use of alternative conceptual models to assess the impact of a buried valley on groundwater vulnerability

A buried valley incised into a sequence of pre-Quaternary sediments is shown to seriously affect the vulnerability of groundwater. Often the existence of buried valleys is not known or is not described explicitly in a hydrogeological model. In the present study, two numerical groundwater models, representing two alternative conceptual models, were produced to help quantify the effect of the valley on groundwater vulnerability. One model included the buried valley and the other did not. Both models were subjected to calibration and were found to describe hydraulic head and river discharge equally well. Even though the two models showed similar calibration statistics; fluxes, travel paths and travel times were affected by the inclusion of the buried valley. The recharge area and the groundwater age of potential abstraction wells placed in the pre-Quaternary deep aquifers surrounding the buried valley were different for the two models, with significantly higher vulnerability when the valley was included in the model. Based on the results of the present study, it is concluded that a buried valley may not always be detectable when calibrating a wrong conceptual model. If reliable results should be obtained a good geological model has to be constructed.     

Evaluation of groundwater availability and sustainable extraction rate for the Upper Santiago Valley Aquifer,Chile

The use of groundwater as water supply has increased dramatically in Santiago, Chile, during the last decades, and there is a need for accurately estimating the actual groundwater supply capacity in the upper Santiago Valley aquifer. The behavior of this aquifer was studied in order to determine the availability of water and the long-range sustainable extraction rate.Water-table depths were simulated using a numerical model with information on recharge from the last 48 years under different extraction policies. With this series of groundwater level data, groundwater level probability distribution functions were determined and extraction statistics were estimated by fitting time series models and by using the crossing theory. With this information, it has been possible to calculate the risk of being unable to supply groundwater demand because the results verify that only 67% of the water rights granted are able to be extracted on a sustained basis with a 90% exceedance probability. Furthermore, the results obtained demonstrate that the method is adequate for determining exceedance probabilities of groundwater flow.

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Resumen El uso de las aguas subterráneas como fuente de abastecimiento se ha incrementado enormemente en Santiago de Chile durante las últimas décadas, por lo que se necesita estimar de forma adecuada la capacidad actual de suministro del acuífero superior del Valle de Santiago. Se ha estudiado el comportamiento de este acuífero para determinar la disponibilidad de recursos y la tasa de extracción sustentable a largo plazo.Se ha simulado los niveles freáticos del acuífero utilizando un modelo numérico con información de la recarga en los últimos 48 años bajo diferentes regímenes de extracción. Con esta serie de datos de los niveles en el acuífero, se ha determinado la distribución de probabilidad de los niveles de las aguas subterráneas y se ha estimado las estadísticas de las extracciones mediante el ajuste de modelos de series temporales y la teoría de cruce. Con esta información, se ha podido calcular el riego de no satisfacer la demanda de abastecimiento, puesto que los resultados verifican que sólo se podría extraer el 67% de las concesiones de agua existentes de manera sustentable con un 90% de probabilidad de excedencia. Aún más, los resultados obtenidos demuestran que el método es adecuado para determinar las probabilidades de excedencia del flujo de las aguas subterráneas.

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Resumé Lutilisation de leau souterraine pour leau potable sest considérablement accrue à Santiago (Chili) au cours des derniers lustres; cest pourquoi il est maintenant nécessaire destimer avec précision la capacité réelle dalimentation de la nappe de laquifère supérieur de la vallée de Santiago. Le fonctionnement de cet aquifère a été étudié afin de déterminer la disponibilité en eau et le taux dextraction durable à long terme.Les niveaux de la nappe ont été simulés avec un modèle numérique à partir dinformation sur la recharge au cours des 48 dernières années pour différentes politiques dextraction. A partir de cette série de données piézométriques, des fonctions de distribution de probabilité des niveaux de la nappe ont été déterminées et des statistiques dextraction ont été estimées par ajustement de modèles de séries chronologiques en utilisant la théorie du croisement. Avec ces informations, il a été possible de calculer le risque de ne pas pouvoir satisfaire la demande deau souterraine, puisque les résultats vérifient que seulement 67% des droits deau attribués peuvent être extraits sur une base durable avec une probabilité de dépassement de 90%. En outre, les résultats obtenus démontrent que la méthode est adaptée à la détermination des probabilités de dépassement de lécoulement souterrain.

     

浅析松原市地下水水位动态及环境问题

随着松原市社会经济的发展,地下水开采量逐年增大,由此引发的环境地质问题逐渐加剧,如地下水水位下降、地下水降落漏斗、水质污染、土壤沙漠化、饮水型地方病问题等等.利用水位动态观测资料,对松原市地下水动态分析,总结了近几年地下水开发利用现状,并针对人类活动所引起的地下水环境问题,提出自己的建议.     

Exploitation of groundwater resources and protection of wetland in the Yuqia Basin

In Yuqia Basin, the climate is arid and the ecologic environment is fragile, and shortage of water resources has seriously restricted the sustainable development of local economy. In order to meet the needs of industrial and domestic water in the Yuqia Basin, numerical simulation was used to evaluate the groundwater resources and potential for exploitation. The results showed that the mathematical model and calculation parameters used were mainly in accordance with practical situation. The calculated value of the underground water level is consistent with measured value during the period of identification and validation. The total recharge of groundwater resources was 22.02×10~4 m~3/d, and the total drainage was 21.95×10~4 m~3/d at present. The Yuqia River leakage is the main supply source of groundwater. There is no significant effect on area of wetland when water source place exploited by 2.5×10~4 m~3/d at alluvial-diluvial fan of Yuqia River. After long-term exploitation, the spring flow reduces from 1.42×10~4 m~3/d to 1.01×10~4 m~3/d and wetland area reduces by 32.7% of original area. The calculation of water balance shows that it is safe to the Yuqia Basin, Da Qiadam Lake, the Mahai Basin at downstream of Yuqia River and wetland under the condition of water source place exploited by 2.5×10~4 m~3/d.     

Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.     

基于数值模拟的岩溶地下水源保护区划分技术研究

以山东省邹城市某岩溶水源地为例,研究数值模拟方法在岩溶地下水水源地保护区划分中的应用,以及水文地质参数对于水源地保护区划分结果的影响。基于GMS软件构建了研究区三维非稳定流地下水数值模型,采用质点追踪技术,通过反向追踪示踪粒子在运移100 d、1 000 d以及25 a后的位置及迁移轨迹,对该岩溶水源地进行保护区划分;改变数值模型中的主要水文地质参数,以变化后的保护区面积作为衡量参数敏感度的指标,并计算各参数的敏感度系数,研究水文地质参数对于保护区划分范围的影响。结果表明:当参数改变幅度在20%范围内时,一层垂向渗透系数(VK1)的敏感度系数最大可达到2.63×10-3,二层垂向渗透系数(VK2)的敏感度系数最大可达到3.64×10-3;垂向渗透系数的敏感度明显高于其他参数,说明垂向渗透系数对保护区划分范围的影响最大。因此,在应用数值模拟法对岩溶地下水源地进行保护区划分时,应尤其注意模型中各含水层垂向渗透系数取值的准确性和合理性。