Aquifer overexploitation: what does it mean?

Groundwater overexploitation and aquifer overexploitation are terms that are becoming common in water-resources management. Hydrologists, managers and journalists use them when talking about stressed aquifers or some groundwater conflict. Overexploitation may be defined as the situation in which, for some years, average aquifer abstraction rate is greater than, or close to the average recharge rate. But rate and extent of recharge areas are often very uncertain. Besides, they may be modified by human activities and aquifer development. In practice, however, an aquifer is often considered as overexploited when some persistent negative results of aquifer development are felt or perceived, such as a continuous water-level drawdown, progressive water-quality deterioration, increase of abstraction cost, or ecological damage. But negative results do not necessarily imply that abstraction is greater than recharge. They may be simply due to well interferences and the long transient period that follow changes in the aquifer water balance. Groundwater storage is depleted to some extent during the transient period after abstraction is increased. Its duration depends on aquifer size, specific storage and permeability. Which level of "aquifer overexploitation" is advisable or bearable, depends on the detailed and updated consideration of aquifer-development effects and the measures implemented for correction. This should not be the result of applying general rules based on some indirect data. Monitoring, sound aquifer knowledge, and calculation or modelling of behaviour are needed in the framework of a set of objectives and policies. They should be established by a management institution, with the involvement of groundwater stakeholders, and take into account the environmental and social constraints. Aquifer overexploitation, which often is perceived to be associated with something ethically bad, is not necessarily detrimental if it is not permanent. It may be a step towards sustainable development. Actually, the term aquifer overexploitation is mostly a qualifier that intends to point to a concern about the evolution of the aquifer-flow system in some specific, restricted points of view, but without a precise hydrodynamic meaning. Implementing groundwater management and protection measures needs quantitative appraisal of aquifer evolution and effects based on detailed multidisciplinary studies, which have to be supported by reliable data. Electronic Publication     

Environmentalism and Natural Aggregate Mining

Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy—hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers—their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is man must live more lightly on the land. The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for living space has encroached on the sites of production; in other words, the act of production has engendered condemnation. Many other environmental problems that are associated with dust and noise and blasting from quarry and pit operations have been reduced through the efficient use of technology. Recycling concrete in buildings, bridges, and roads and asphaltic pavements will ultimately reduce the demand for virgin natural aggregate. The impact created by the large holes in the ground required for the mining of natural aggregate can be greatly reduced by planning their reclamation before mining begins.     

江苏省露采矿山地质环境综合评价研究

本文以江苏省露采矿山地质环境调查资料为基础,采用层次分析法,通过露采矿山地质灾害易发性和自然环境影响程度两方面的12个评价指标,建立江苏省露采矿山地质环境综合评价体系。在确定各评价指标权重和评价分级标准的基础上,以ARCGIS作为系统运行平台,生成江苏省露采矿山地质灾害易发性区划图、自然环境影响程度区划图、矿山地质环境综合区划图。     

铁法矿区采煤沉陷区的发展演化趋势分析

通过对矿区采煤沉陷区的调查，对影响沉陷形成的主要因素(煤层的厚度、煤层的埋藏深度、上覆底层的物理力学性质、松散层的厚度、矿井开采条件等)进行了针对性的分析，并对将来煤炭采空区的地面沉陷情况(至2010年末，区内将再形成约55km^2的沉陷与变形区)进行了预测，为该矿区地面沉陷的综合治理提供依据。     

非规则采矿工作面积分区间确定方法

针对工作面形状多种多样的特点,本文采用二次曲线描述工作面水平投影边界,并且利用分段积分的方法处理更加复杂的工作面形状,合理地解决了非规则采矿工作面积分区间的划分问题;同时,给出了工作面形状系数的计算公式,整个计算过程利用计算机技术实现自动解算,避免了对任意曲边形工作面采用矩形分割的近似处理方法,提高了地面沉陷预计精度。最后,用实例说明了本文提供的对非规则采矿工作面的处理方法比现行处理方法具有更高的     

乌达矿区高硫煤层的聚积环境与煤中硫的分布

对乌达矿区高硫煤层的沉积相、煤相和煤中硫在平面上的分布进行了研究。结果表明,１０煤层泥炭聚积时的古水系对煤中硫的分布有明显的影响,９煤层泥炭聚积时的三环境决定了煤中硫的分布,浅水陆棚或分流间湾环境中形成的煤层具有较高ＧＩ、Ｖ／Ｉ值和硫含量,在障壁砂坝中形成的煤层具有高的硫含量、低的ＧＩ、Ｖ／Ｉ值,在泻湖中具有高ＧＩ、Ｖ／Ｉ值和相对较少的硫含量。     

平果那豆铝土矿矿体产出地质特征及开采技术条件

广西平果岩溶堆积型铝土矿是一种新的工业类型,规模大,埋藏浅,易采易选,矿床地质特征独特,属低硅中铝高铁型。     

硫铁矿焙烧灰渣中铊分布规律及环境效应的研究

利用分光光度法测定了铊在硫铁矿焙烧灰、渣中的含量,探讨了含铊硫铁矿燃烧后铊在灰渣中的集散规律及其对环境影响。结果显示硫铁矿焙烧灰渣中铊含量远高于克拉克值和土壤背景值;与原矿石相比,铊在炉灰中富集,炉渣中含量减少。硫铁矿燃烧产生的含铊灰渣对环境危害增大。     

云南永善金沙矿区的上部铅锌矿床

笔者对金沙矿区的上部铅锌矿床（上部矿）,从含矿建造、矿体产出（产状）、形态、矿石物质组分和结构构造等特征,通过稀土元素和有机地球化学的分析对比,笔者认为金沙矿区上部矿与下部矿完全不同。上部矿床属于沉积－成岩－有机成因。     

Sulfur Isotope Study and Re-examination of Ore Mineral Assemblage of the Hol Kol and the Tul Mi Chung Skarn-type Copper–Gold Deposits of the Suan Mining District, Korean Peninsula

Abstract: Ore specimens collected by the late Professor Takeo Watanabe from the Hol Kol and the Tul Mi Chung deposits, Suan mining district, Korean peninsula, were examined. In addition, measurements of sulfur isotopic ratio of ores and preliminary fluid inclusion microthermometry were carried out. Ores from the New orebody of the Hol Kol deposit consist mainly of bornite, wittichenite and chalcopyrite presently, which exhibit lamellae intergrowth texture, associated with native bismuth and electrum. Bismuthian bornite solid solution is considered to be a principal initial phases, while native bismuth was nucleated as molten bismuth melt initially. The occurrence of cubanite, miharaite, carrollite, siegenite, hessite and geikielite are recognized from the New orebody. Ores from the Eastern orebody of the Hol Kol deposit consist chiefly of chalcopyrite, occasionally associated with trace amounts of pyrrhotite, pyrite, bismuthinite and rare tellurobismuthite, while an ore specimen from the Western orebody consists mainly of sphalerite associated with chalcopyrite, pyrite and galena. Ores from the Tul Mi Chung deposit consist mainly of chalcopyrite and pyrite, occasionally associated with magnetite, sphalerite, galena and rare molybdenite. Some portions of magnetite are revealed to be silician magnetite. Sulfur fugacity is supposed to be below the stability field of bismuthinite in the New orebody. A reducing condition is suggested by the occurrence of geikielite without Fe³⁺ content. The sulfur and oxygen fugacities for the Eastern and Western orebodies of the Hol Kol deposit and for the Tul Mi Chung deposit were higher than the New orebody of the Hol Kol deposit. On the other hand, the Suan granite (porphyritic granodiorite) and the Chil Sing Dai granite (biotite granite porphyry) from the Hol Kol area can be classified as weakly magnetic magnetite‐series. Polyphase fluid inclusions are observed in gangue diopside associated with Cu ore of two specimens. The dissolution temperatures of daughter crystals are 394±26°C and 442±45°C, while the disappearing temperatures of vapor bubble were 475±25°C and > 500°C. Highly saline fluids were responsible for the mineralization at the Hol Kol deposit. The δ³⁴S values of ore sulfides of the Hol Kol and the Tul Mi Chung deposit range from +11. 5% to +16. 1%, having anomalous lower values mainly from the Tul Mi Chung deposit. Such anomalous lower 6³⁴S values can be caused by isotopic fractionation against oxidized sulfur species. The δ³⁴S value of bulk sulfur in the ore solutions responsible for the Hol Kol and the Tul Mi Chung deposit is estimated to be +13.5±2.5‰.