许昌麦岭水源地可开采量的水均衡法计算

根据许昌麦岭镇多年地下水动态观测资料,利用水均衡法原理,对水源地边界地质条件、补给与排泄的关系进行研究,对地下水允许开采量进行综合评价,提出水源地水量开采的建议。     

天津市地下水资源与可持续利用

天津市是我国主要缺水城市之一。1990～2000年地表水年平均用水量16 33×108m3,地下水年平均用水量7 11×108m3,地下水的供水比例约占30%左右。1990～2002年,按全国统一部署,对天津市地下水资源进行了新一轮评价,评价结果是天津市地下水天然资源为18 13×108m3 a,矿化度小于5g L的天然资源为15 75×108m3 a,可开采资源为8 27×108m3 a,其中浅层水2 58×108m3 a,深层水3 56×108m3 a,隐伏岩溶水1 24×108m3 a,山区1 10×108m3 a。天津市地下水开采程度已达90 45%,除蓟县、宝坻、宁河、静海略有盈余,其余各区、县已超采。要解决天津市规划需水量(2010年)56 76×108m3 a的要求,必须采取外调水源、工农业节水和污水回收利用、海水淡化利用、利用坑、塘、洼、淀尽可能拦蓄汛期弃水等措施。天津市每年7×108～8×108m3的地下水资源为多年稳定补给的地下水资源,属可持续利用的水资源,但必须调整开采布局,压缩深层水的开采量,以遏制地面沉降继续发展。在连续干旱年份,为解决城镇生产及生活用水的燃眉之急,保证城市供水安全,建立一种非常规的并有一定开采周期的应急供水水源地,可缓解一部分供水压力。经初步论证,蓟县平原区和宝坻中北部第四系全淡水区及邻近的咸水分布区,有望建成大型集中供水水源地。经勘查,蓟     

鄂尔多斯盆地中生代晚期以来大地热流的变化及其对生态环境格局和演变的影响

鄂尔多斯盆地的西北部、东北部和南部三个区域现今大地热流平均值分别为56．3、67．3和65．3mW／m^2，对应的生态环境格局也有明显的差异。研究表明，大地热流每增加4～5mW／m^2可使年均地表温度升高约l℃，使最低月均地表温度升高2。C以上。鄂尔多斯盆地东北部的平均大地热流比西北部高出11mW／m^2，东北部年均地表温度可能比西北部高出2～3℃，其最低月均地表温度可能比西北部高出4～6℃。西北部的大地热流平均值已经低于维持地表生态系统延续所需大地热流的临界值(57mW／m^2)，其自然生态系统整体上已经处于脆弱境地；东北部和南部的大地热流均大于57mW／m^2，自然生态系统均尚较稳健。东北部的沙漠化可能是风沙侵入的结果，其生态应该是可以恢复的。整个西北部作为一个整体看，72万年以前大地热流就已衰减到临界值以下，区域生态系统渐趋脆弱，开始整体上向荒漠化演变。     

疏降地下水引起地面塌陷浅析--以淮南煤矿区为例

以淮南西部矿区为例，介绍了该地区自20世纪60年代开采煤矿以来，由于疏降地下水，引起的地面塌陷。为了研究灰岩水动力场规律，先后在该区进行多时段、多水平放水试验。研究表明，覆盖粘土层、岩溶及人工疏降地下水，是该地区岩溶塌陷形成的基本条件。通过对粘土盖层性质、疏降地下水岩溶塌陷演化过程及塌陷机理与对应阶段过程综合分析，结合区域地质条件，掌握了塌陷点的分布规律。对目前西部地区塌陷“复活”、整治及未来城市规划，提出了建设性建议。     

陕西渭北东部岩溶水环境同位素

陕西渭北东部岩溶水系统是一个复杂的地下水系统，碳酸盐岩大面积隐伏与深埋。使用传统手段和方法勘查岩溶地下水和研究可持续开发利用方案遇到诸多困难，不仅费时，而且耗资大。本文通过系统分析研究陕西渭北东部地区岩溶地下水T、D、^180、^14C环境同位素特征，揭示岩溶水的补给迳流排泄条件、岩溶水系统边界性质以及岩溶水与黄河洛河地表水、黄河岩溶泉与洛河岩溶泉之间的补排关系。结果显示环境同位素方法简便有效，能够达到预期目的。     

Hydro-thermal performance of multilayer capillary barriers in arid lands

In this study, a capillary barrier system was designed and tested for an arid land environment. To simulate arid land conditions of high temperature and sub-irrigation systems, the barrier was subjected to thermal and hydraulic gradients in opposite directions; to test the barrier system under these severe conditions, an experimental apparatus was designed and fabricated. The multilayer capillary barrier consisted of three layers made of silica sand, a mixture of sand and bentonite in equal portions, and a mixture of clay (25%) and aggregate (75%). Several one dimensional coupled heat and moisture tests were performed. Temperature variations along the thickness of the barrier were recorded as a function of time, and at the end of each test, the barrier was sliced into small sections, for the determination of volumetric water content as a function of distance from the heat source. The experimental results were discussed in view of the barrier's intended purpose of its ability to store moisture for long time durations. Coupled heat and moisture flow equations were developed and solved numerically via a finite difference method. Diffusivity parameters were calculated by using experimental results, a numerical model, and Powell's conjugate directions method of nonlinear optimization. The model was calibrated and the results were discussed. Good agreement between calculated and experimental results was obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

Meteorological Office, Pune-411 005

Natural disasters like floods, tornadoes, tropicalcyclones, heat and cold wavewreak havoc and cause tremendous loss ofproperty all over the world. Most ofthe natural disasters are either dueto weather or are triggered due toweather related processes.Extreme weather events claimed thousands oflives and caused damage on vastscale. Recent super cyclone which affectedOrissa in 1999, Bangladesh cyclone of1970 and Hurricane Andrew in 1992 areexamples of some of the more damagingtropical cyclones which affected developingas well as the developed world. Heatand cold waves are also extreme events,which cause enormous losses in terms oflives lost and human discomfort and ailmentsarising out of them. The heat waveof 1995 and 1998 are still fresh in the mindof the Indian public. The estimated lossof human lives due to heat wave in 1998 was morethan 15,000. Economic losses asa result of these disasters and in particular inassociation with tropical cyclones haveincreased enormously over the last three decades.During 1961–1991, total loss oflives from drought alone was 1,333,728 overthe whole world. In terms of economiclosses, there is 8–10 fold increase from thebase figure of 1960. The socio-economicimpact of natural disaster is complex dependingupon the vulnerability of the placeand mitigation strategies that are put in place.Meteorology plays a crucial role in forewarningpeople about the severe/extremeweather systems and a constant endeavour by themeteorological services worldover has gone a long way towards minimizing thelosses caused by natural disasters.The paper summarises the natural disasterstatistics over south Asia and the possibleprediction strategies for combating theirsocio-economic impacts.     

Curie Point Depths Beneath Precordillera Cuyana and Sierras Pampeanas Obtained from Spectral Analysis of Magnetic Anomalies

A gravity and magnetic survey has been carried out with the purpose of investigating geophysical features of the crusts beneath three geological provinces in western Argentina: Cuyo Precordillera, the Sierras Pampeanas of San Juan and La Rioja, and Famatina System, the results of which are displayed in three maps: Bouguer anomaly, total field magnetic anomaly and total field reduced to the pole.

The top and bottom boundaries of the magnetized crust were calculated from power-density spectra of the total-field anomalies from our terrestrial database in 90 2D windows. The depths obtained for the bottom of magnetized crust are assumed to correspond to Curie point depths. The values thus obtained for the Precordillera range between 29 and 40 km, whereas for the Sierras Pampeanas, in the Sierra de Pie de Palo, and other mountain chains along the Bermejo-Desaguadero lineament or Valle Fértil lineament, such depth ranges between 20 and 35 km. These results are consistent with Curie point depths determined on different continental regions in the world.

A map of regional heat flow has been prepared in the present work based on the depth of the Curie point isotherm, which shows that heat flow patterns in Precordillera are different from those found in Sierras Pampeanas.

A significant heat flow extending in Northeast-Southwest direction seems to be directly related to Juan Fernández Ridge trace.

The results of the present investigations also point out a possible relationship between the base of the magnetized crust and the boundary separating the brittle from the ductile crustal regime.     

The structural role of Ti in aluminosilicate liquids in the glass transition range: insights from heat capacity and shear viscosity measurements

The shear viscosities and 1 bar heat capacities of glasses and melts along the 67mol% silica isopleth in the system SiO₂-Al₂O₃-Na₂O-TiO₂ have been determined in the temperature ranges 780-1140 K and 305-1090 K respectively. Anomalous behaviour of both these properties is observed for compositions rich in TiO₂ and/or Al₂O₃, an observation attributed to liquid-liquid phase separation followed by anatase crystallization. For samples which do not show anomalous behaviour, it is found that the partial molar heat capacity of the TiO₂ component previously determined in Al-free compositions reproduces our heat capacities to within 1.3%. Viscosity data show that addition of TiO₂ tends to increase viscosity and melt fragility at constant temperature. Furthermore, heat capacity and viscosity data may be combined within the framework of the Adam-Gibbs theory to extract values of the configurational entropy of the liquids and qualitative estimates of the variation of the average energy barrier to viscous flow. Configurational entropy at 900K is inferred to decrease upon addition of TiO₂, in contrast to previous results from Al-free systems. The compositional limit separating normal from anomalous behaviour, as well as the data for homogenous melts have been used to constrain the structural role of Ti in these samples. Our data are consistent with a majority of Ti in five-fold coordination associated with a titanyl bond, in agreement with previous spectroscopic studies. Furthermore, we find no evidence for a Ti-Al interaction in our samples, and we are led to the conclusion that Al and Ti are incompletely mixed, a hypothesis consistent with the observed reduction of configurational entropy upon addition of TiO₂, suggesting an important role of medium range order in controlling the variations in thermodynamic properties.     

沙漠增温效应特征及绿洲农业热量资源分异规律的研究

为了进一步认识绿洲高效农业特殊的热量资源，通过研究沙漠增温效应特征表明：沙漠增温效应强弱随距离沙漠远近而不同，100km范围内沙漠对绿洲的平均增温为1．76℃；另外增温效应导致绿洲日、年温差大、干热风及冷害等气候特征；由于沙漠的面积、地貌特点等的差异，使增温效应产生原因及作用程度不尽相同，表现出绿洲农业资源分异规律，并将西北干旱区绿洲分为5个类型区。