Ground-Water pollution and its sources

Everybody wants clean water for drinking, bathing and other domestic uses, but not everybody appreciates the fact that our own actions are often the worst enemy in achieving that goal. Ground water is one of the most misused and misunderstood resources. Because ground water and its movement, and consequently also its pollution, is hidden from view beneath the land surface, the seriousness of ground-water pollution problems has not been recognized until recently. The sources of ground-water pollution are many and varied because in addition to natural processes practically every type of facility or structure installed by man and each and every one of his activities may eventually contribute to ground-water quality problems. The quality of ground water is most commonly affected by waste disposal. Other major sources result from agricultural activities and ground-water development. In addition to these three major categories, there are other potential sources of pollution, such as mining, spills, leakage from underground pipes and tanks, and road salting. All of these activities can generate pollutants which eventually may enter the ground-water systems and slowly begin to move through the subsurface environment. Once under the ground, the pollutants are hidden from view and the existence of ground-water pollution becomes evident only if they reemerge on the surface or in water wells. When this occurs, it is almost too late to do anything about it. The effects of pollution may remain in the aquifers for years, decades, or centuries, because the residence time (turnover) of ground water is very slow. Ground-water pollution may even result in aquifers or parts of quifers being damaged beyond repair.     

矿坑涌水量的平滑预测及其若干问题

介绍了指数平滑法的基本思想、公式及应用实例,并探讨了它在矿坑涌水量预测应用中的几个问题.     

Human interactions with ground-water

Ground-Water could be considered as an immense reservoir, from which only a certain amount of water can be withdrawn without affecting the quantity and quality of water. This amount is determined by the characteristics of the environment in which ground-water occurs and by the interactions of ground-water with precipitation, surface water, and people. It should be recognized that quantity and quality of ground-water are intimately related and should be considered accordingly. Quantity refers to usable water and water is usable for any specific purpose only so long as its quality has not deteriorated beyond acceptable limits. Thus an overall quantitative and qualitative management of ground water is inevitable, and its should also involve the uses of ground-water reservoirs for purposes other than water supply. The main objective of ground-water management is to ensure that ground-water resources will be available in appropriate time and in appropriate quantity and quality to meet the most important demands of our society. Traditional, and obvious uses of ground-water are the extraction of water for water supplies (domestic, municipal, agricultural, and industrial) and the natural discharge feeding lakes and maintaining base flow of streams. Not so obvious are the uses of ground-water reservoirs, the very framework within which ground-water occurs and moves, and in which other fluids or materials can be stored. In the last two decades, ground-water reservoirs have been intensively considered for many other purposes than water supplies. Diversified and very often conflicting uses need to be evaluated and dealt with in the most efficient way in order to determine the importance of each possible use, and to assign priorities of these uses. With rising competition for the use of ground-water reservoirs, we will also need to increase the potential for effective planning of ground-water development and protection. Man's development and use of ground-water necessarily modifies the natural conditions and the total natural system must be successfully blended with the unnatural stresses placed upon it. This can be accomplished by introducing new methods (such as ground-water zoning) in and by developing alternative strategies for ground-water management and protection.     

Use and availability of ground-water

Every man has to consume a certain quatity of water every day. This use constitutes the most basic need for water. In households water is also used for basic hygiene, washing, cleaning, and for the transport of sewage. Water is used in industry for cooling, generating electric power, for the production of a large variety of goods, and other purposes. The greatest demand for water results from irrigation. To satisfy these demands, an increasing quantity of ground-water is used. It is available at many places, where far extended subsurface reservoirs exist; it is better protected against pollution than surface water. But even though ground-water exists in many geological formations, which seem to be infinite, the availability is limited. The recharge of ground-water is dependent on the supply of atmospheric moisture. Especially in semiarid and arid zones this component of the hydrologic cycle determines the availability of ground-water. Besides natural conditions, technical and economic factors such as drilling of boreholes and the cost of pumping of ground-water have to be considered. Also political decisions can limit the availability of ground-water. If, for instance, wetlands are destroyed by drawdown of ground-water, nontechnical and non-economical aspects are involved. We face undesirable effects of ground-water pumping. Whether these effects are tolerable or intolerable depends on the decision-making processes on a political level.     

Estimating ground-water recharge from streamflow records

The purpose of this paper is to estimate ground-water recharge based on the investigation of the balance between ground-water recharge and discharge from streamflow hydrographs. Two methods of hydrograph analysis are employed in a case study of Cho-Shui River basin, Taiwan. The first is the recession-curve-displacement method, which assumes the linearity of the master recession curve while the profile of the ground-water head distribution is nearly stable. The second method is the base-flow-record estimation, which uses a relatively arbitrary procedure to estimate a continuous record of ground-water discharge (baseflow) under the streamflow hydrograph. Through implementing these two methods, the annual rates of ground-water recharge and infiltration in the area of Cho-Shui River basin are examined as our case study. Results showed that the discharge calculated by the method of base-flow-record estimation is about 16% average less than the recharge calculated by the recession-curve-displacement method in the mountain region.     

淮安城市化进程中的地质环境问题探讨

在分析淮安市基本地质环境特征的基础上.总结淮安城市化进程中的地质环境问题.这些地质环境问题主要表现在地震、地下水位下降、地面沉降、水污染、同体废弃物、地面变形、软土变形和液化土地基.最后在分析其地质和城市化成因的基础上,提出相应的城市地质环境保护对策.     

Ground-water models for water resource planning

In the past decade hydrogeologists have emphasized the development of computer-based mathematical models to aid in the understanding of flow, the transport of solutes, transport of heat, and deformation in the ground-water system. These models have been used to provide information and predictions for water managers. Too frequently, ground-water was neglected in water resource planning because managers believed that it could not be adequately evaluated in terms of availability, quality, and effect of development on surface-water supplies. Now, however, with newly developed digital ground-water models, effects of development can be predicted. Such models have been used to predict hydrologic and quality changes under different stresses. These models have grown in complexity over the last ten years from simple one-layer models to three-dimensional simulations of ground-water flow, which may include solute transport, heat transport, effects of land subsidence, and encroachment of saltwater. Case histories illustrate how predictive ground-water models have provided the information needed for the sound planning and management of water resources in the USA.     

Effect of highly pervious geological features on ground-water flow into a tunnel

Current practice for estimating water inflow rate relies mostly on analytical solutions which assume a homogeneous, isotropic porous medium around a tunnel. Field measurements indicate that current engineering practice does not consistently make adequate estimate of ground-water flow into a tunnel during excavation due to various factors that analytical solutions do not properly take into account. Among the various factors affecting ground-water flow, the significance of a highly pervious feature located near the tunnel is discussed in this research. The highly pervious feature, which is located near an underground opening and connected to a large source of water, can provide a path for relatively high-head water to the joints intersecting the opening. This paper describes the influence of a highly pervious feature on the ground-water flow regime around a tunnel and the change of inflow rate as the tunnel approaches a highly pervious feature.     

Mineral and thermal waters of Western Bohemia

Mineral and thermal waters are a special kind of ground-water, distinguished by specific chemical or physical properties such as higher mineralization, concentration of certain constituents, dissolved gas, radioactivity, or temperature. Hydrologically, they are a part of ground-water system. Mineral or thermal waters are usually connegted with specific and unique geological and tetuunic structure.. The classical territory of mineral and thermal waters is Europe, where these waters have been used for medicinal purposes since ancient times. The development of spas and increased demands for mineral water for spa operation necessitated increased knowledge of spring structures and the development of optimal balneotechnical works. These problems are discussed on the examples of the Karlovy Vary Spa (Karlsbad) and Jàchymov Spa (St. Jachimstha) in W Bohemia. The location of mineral springs in the Karlovy Vary Spa, the largest spa in Czechoslovakia, in a highly urbanized area required a thorough investigation and unique methods for capturing thermal water at a greater depth to provide a steady supply of thermal water and to protect the springs against pollution from the surface. The Jachymov radioactive thermal springs, which were accidentally discovered in a deep, subsurface uranium mine, present a unique problem of protecting the stability of spring's regime in a mining environment.     

State and local response to damaging land subsidence in United States urban areas

Land subsidence caused by man-induced depressuring of underground reservoirs has occurred in at least nine urban areas in the United States. Significant efforts to control it have been made in three areas: Long Beach, California; Houston-Galveston, Texas; and Santa Clara Valley, California. In these areas coastal flooding and its control cost more than $300 million. Institutional changes were required in each area to ameliorate its subsidence problem.

In Long Beach and Houston-Galveston, efforts were made to mitigate subsidence only after significant flood damage had occurred. To arrest subsidence at Long Beach, the city lobbied for a special state law, the California Subsidence Act, that required unitization and repressuring of the Wilmington oil field. In the Houston-Galveston region, the Texas State Legislature authorized formation of the Harris-Galveston Coastal Subsidence District with authority to regulate ground-water pumping by permit. This solution, which was achieved through efforts of entities affected by subsidence, was the product of a series of compromises necessitated by political fragmentation and disjointed water planning in the region. Amelioration of subsidence in the Santa Clara Valley was a collateral benefit from the effort by water users to curtail ground-water overdraft in the valley. Importation of surface water and a tax on ground-water pumpage reduced ground-water use, thereby allowing the recovery of water level and the arresting of subsidence.     

The measurement of Ra/Ra activity ratios in ground water as a uranium exploration technique

Measurements were made of the ²²⁶Ra/²²³Ra activity ratio in ground waters obtained from drill holes in the vicinity of uranium mineralization in northern Saskatchewan where certain hydrologic parameters, specifically ground-water velocity and direction, had been determined. The results show that it is possible to approximate the distance from a ground-water sampling point to the area of mineralization owing to differences in the half lives of the two radium nuclides.The theoretical basis for the determination of the distances is explained.     

双层介质中潜水井稳定渗流的有限单元分析

均质含水层中的自由水面(潜水)问题,虽然有各种各样的分析解和近似解,但对非均质条件还缺乏合理的解答。目前虽可采用虚构流网的概念相当准确地计算侧向补给情况的潜水井流量,但由于这种方法不能计算渗流场的水头分布,仍不易把它引用到不稳定渗流问题中去。     

Migrating pingos in the permafrost region of the Tibetan Plateau, China and their hazard along the Golmud–Lhasa railway

Most pingos in the permafrost region of the high northern Tibetan Plateau form along active fault zones and many change position annually along the zones and thus appear to migrate. The fault zones conduct geothermal heat, which thins permafrost, and control cool to hot springs in the region. They maintain ground-water circulation through broken rock in an open system to supply water for pingo growth during the winter in overlying fluvial and lacustrian deposits. Springs remain after the pingos thaw in the summer. Fault movement, earthquakes and man's activities cause the water pathways supplying pingos to shift and consequently the pingos migrate.

The hazard posed to the new Golmud–Lhasa railway across the plateau by migrating pingos is restricted to active fault zones, but is serious, as these zones are common and generate large earthquakes. Pingos have damaged the highway and the oil pipeline adjacent to the railway since 2001. One caused tilting and breaking of a bridge pier and destroyed a highway bridge across the Chumaerhe fault. Another has already caused minor damage to a new railway bridge. Furthermore, the construction of a bridge pier in the North Wuli fault zone in July–August 2003 created a conduit for a new spring, which created a pingo during the following winter. Measures taken to drain the ground-water via a tunnel worked well and prevented damage before the railway tracks were laid. However, pier vibrations from subsequent train motion disrupted the drain and led to new springs, which may induce further pingo growth beneath the bridge.

The migrating pingos result from active fault movement promoting artesian ground-water circulation and changing water pathways under the seasonal temperature variations in the permafrost region. They pose a serious hazard to railway construction, which, in turn can further disturb the ground-water conduits and affect pingo migration.     

上海实行地下水“分质供水,优质优用”的利与弊

着重论证了在浦东待开发的新区,实行地下水“分质供水,优质作用”的利与弊。从量上分析,能够保证浦东饮用水和部分尖端产品水处理的发展需要。从质上分析,不易受污染的优质干净地下水只要合理开发,是不会引起环境地质问题的。因而,必须彻底改变百年一贯制传统的供水方式和结构,以法严格管理,建立起以水养水,保护宝贵资源的良性循环的轨道。     

Enhancement of aquifer vulnerability indexing using the analytic-element method

Indexing methods are used for the evaluation of aquifer vulnerability and establishing guidelines for the protection of ground-water resources. The principle of the indexing method is to rank influences on groundwater to determine overall vulnerability of an aquifer to contamination. The analytic element method (AEM) of ground-water flow modeling is used to enhance indexing methods by rapidly calculating a potentiometric surface based primarily on surface-water features. This potentiometric map is combined with a digital-elevation model to produce a map of water-table depth. This is an improvement over simple water-table interpolation methods. It is physically based, properly representing surface-water features, hydraulic boundaries, and changes in hydraulic conductivity. The AEM software, SPLIT, is used to improve an aquifer vulnerability assessment for a valley-fill aquifer in western New York State. A GIS-based graphical user interface allows automated conversion of hydrography vector data into analytic elements.     

The Lar Dam; an example of infrastructural development in a geologically active karstic region

The problems associated with the construction of the Lar Dam, Iran, provide a classic example of problems that can result from infrastructural development in an active geological terrain which includes the regional carbonate units. The Lar Dam lies in a heavily faulted and fractured region close to the active Damavand volcano. The fracturing has enhanced the production of karst and sinkholes in the limestone below the dam, and acidic ground-water run-off from the Damavand volcano increases the dissolution of the carbonate beds along the fractures to produce sinkholes below the dam. The initial problem of building the dam in such a region is compounded by the relationship between water loss due to enhanced sinkhole development and the remedial measures being taken to lessen this leakage. Drainage of the sub-reservoir caverns through leakage along fractures can lead to loss of hydrostatic support for the developing sub-reservoir caverns, and their consequent collapse. Furthermore, rapid changes in subterranean water levels would lead to rock-shattering hammer effects particularly during rapid rises in water level.     

Fresh and brackish ground-water under coastal areas and islands

Brackish ground-water bodies under coastal areas and islands often show a regular pattern as to the form and salt content. Two types of theories give an explanation, the Badon GHijben/Herzberg (BGH) approach, based on density differences; and theories on mixing phenomena, like diffusion and disperson. The underlying assumptions of both approaches and their respective merits are discussed. The BG g approach is particularly suited to coastal strips and small islands, whereas the mixing theories give better results for more inland areas. This conclusion is illustrated by a number of case studies, two of them concerning the lowlands of the Netherlands and two others dealing with small oceanic islands. The theoretical aspects of the problem of maximum yield of individual wells and drains situated above brackish ground-water are introduced and some solutions are presented.     

列车行车荷载作用下富水弹性砂性地基动态响应

由于轨道的不平整性,列车运行中会产生较大的激振荷载。该激振荷载使铁路路基和地基发生动态响应。铁路路基过大的振动反应会对列车的通行安全不利,降低乘车的舒适性,而且会对铁路周边的建筑物带来不良振动,给周围居民带来噪音污染。所以研究和评估列车通过时铁路路基和地基的动态响应具有重要的实际意义。本文以Biot动态方程为控制方程,以有限元程序包FSSI-CAS 2D为数值计算工具,在前人研究的基础上,进一步深入研究了铁路路基、富水砂性地基在列车行车动荷载作用下的动态响应问题。考虑铁路路基和地基中地下水面线以上部分的非饱和带的存在是本研究的一个特色之处。数值计算表明在列车行车激振荷载作用下,铁路路基-地基系统发生强烈的动力响应,其中以低频的竖向响应为主; 并且该响应存在衰减。非饱和带内的负孔隙水压力在列车激振荷载作用下不发生变化,而饱和带内孔隙压力发生振荡。本文所提供的研究方法、工具和计算案例可为铁路交通工程中评价列车通过的安全性、乘车的舒适性提供研究参考。     

Natural processes controlling the behaviour of contaminants in ground-water

GeoJournal - The concentration and migration of contaminants in ground-water is influenced by many geochemical, physical, and biological processes. The mobility of inorganic and organic...