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1.
The role of faulting on surface deformation patterns from pumping-induced groundwater flow (Las Vegas Valley, USA) 总被引：1，自引：0，他引：1
Land subsidence and earth fissuring can cause damage in semiarid urbanized valleys where pumping exceeds natural recharge. In places such as Las Vegas Valley (USA), Quaternary faults play an important role in the surface deformation patterns by constraining the migration of land subsidence and creating complex relationships with surface fissures. These fissures typically result from horizontal displacements that occur in zones where extensional stress derived from groundwater flow exceeds the tensile strength of the near-surface sediments. A series of hypothetical numerical models, using the finite-element code ABAQUS and based on the observed conditions of the Eglington Fault zone, were developed. The models reproduced the (1) long-term natural recharge and discharge, (2) heavy pumping and (3) incorporation of artificial recharge that reflects the conditions of Las Vegas Valley. The simulated hydrostratigraphy consists of three aquifers, two aquitards and a relatively dry vadose zone, plus a normal fault zone that reflects the Quaternary Eglington fault. Numerical results suggest that a 100-m-wide fault zone composed of sand-like material produces: (1) conditions most similar to those observed in Las Vegas Valley and (2) the most favorable conditions for the development of fissures to form on the surface adjacent to the fault zone. 相似文献
2.
Noble gas recharge temperatures and the excess air component 总被引：1，自引：0，他引：1
The calculation of a groundwater recharge temperature based on the dissolved concentrations of Ne, Ar, Kr and Xe requires a correction for noble gas supersaturation due to excess air entrainment. This entrainment is commonly attributed to the recharge process or to air contamination at the wellhead during sample collection. With the exception of some local studies, most work has concentrated on interpretation of the recharge temperature or quantification of the radiogenic content for palaeoclimatic and dating purposes. The magnitude and source of the excess air is not directly relevant to these studies and so is often ignored. In this work, excess air Ne and other data have been calculated from new and published noble gas data sets for several groundwater systems. For younger groundwaters which have been recharged under one broad climatic regime, the amount of air entrainment increases according to lithology in the order granites, sandstones and limestones respectively. A negative correlation between precipitation and excess air entrainment is identified in at least one aquifer, and some of the mechanisms which may influence the entrainment process are discussed. 相似文献
3.
Spring and Snake valleys, western USA, are scheduled for development and groundwater export to Las Vegas, Nevada (USA). New work, compared to published studies, illustrates the critical role of conceptual models to underpin water withdrawals in arid regions. Interbasin flow studies suggest that 30–55?% of recharge to Snake Valley arrives from adjacent Spring Valley. This study, however, suggest little or no interbasin flow; rather, Spring and Snake valleys comprise separate systems. Contrary to expectation, δD and δ18O contours are perpendicular to proposed interbasin flow paths. 14C age gradients up to 10?ka along interbasin flow paths indicate that old waters are not displaced by such fluxes. 14C and 3H patterns indicate local recharge occurs in adjacent mountain ranges and is transferred to basin-fill by losing streams, mountain front recharge, and upward leakage from carbonate bedrock beneath basins. The choice of conceptual models is critical for groundwater development. Simple analyses of water withdrawals indicate that monitoring discharges at desert springs is an inadequate protective measure. Once flows decline, recovery is lengthy even if pumping is stopped. The conceptual framework behind quantitative evaluations of sustainable yield is critical to determine the ability of a groundwater system to deliver sustained withdrawals. 相似文献
4.
Stable isotope data, a dissolved gas tracer study, groundwater age dating, and geochemical modeling were used to identify and characterize the effects of introducing low-TDS recharge water in a shallow aerobic aquifer affected by a managed aquifer recharge project in California’s San Joaquin Valley. The data all consistently point to a substantial degree of mixing of recharge water from surface ponds with ambient groundwater in a number of nearby wells screened at depths above 60 m below ground surface. Groundwater age data indicate that the wells near the recharge ponds sample recently recharged water, as delineated by stable O and C isotope data as well as total dissolved solids, in addition to much older groundwater in various mixing proportions. Where the recharge water signature is present, the specific geochemical interactions between the recharge water and the aquifer material appear to include ion exchange reactions (comparative enrichment of affected groundwater with Na and K at the expense of Ca and Mg) and the desorption of oxyanion-forming trace elements (As, V, and Mo), possibly in response to the elevated pH of the recharge water. 相似文献
5.
本文采用TOUGH2数值模拟软件,根据研究区对井在预设情景下运转30年的模拟结果,对河南省延津县下新近系热储层压力场、温度场进行模拟,在模型验证的基础上,对不同回灌率及不同采灌井间距工况进行模拟研究,结果显示:回灌井的回灌过程会使地下水水温降低,回灌时间越长水温降低幅度越大,影响范围也越大,根据模拟抽水井和回灌井不同间距条件下(55 m、150 m、250 m、300 m)温度场变化情况,建议区域下新近系地层地热回灌项目抽水井和回灌井间距应大于等于250m,以保证抽水井出水温度;而不同回灌率工况下分析化学场和压力场的模拟数据可以看出,回灌率越大,地热水水质、压力影响越大,基本呈线性关系。为区域地热资源回灌-开采提供示范和指导。 相似文献
6.
Johannes Holocher Frank PeetersWerner Aeschbach-Hertig Markus HoferMatthias Brennwald Wolfgang KinzelbachRolf Kipfer 《Geochimica et cosmochimica acta》2002,66(23):4103-4117
The formation of an excess of dissolved gas (“excess air”) in quasi-saturated media was studied by analyzing and interpreting dissolved noble gas concentrations in laboratory column experiments. Using quartz sand filled columns of 1 m length, two different experimental designs were realized. In the first, groundwater recharge was simulated by a unidirectional vertical water flow through the columns. In the second, groundwater level fluctuations in an aquifer zone without active infiltration were reproduced by cyclic water level fluctuations in the columns. The reproducible generation of excess air under these defined, near natural conditions was successful. Partial or complete dissolution of air bubbles entrapped in the quartz sand could be identified as the mechanism responsible for the generation of excess air. Depending on the experimental design, supersaturation of the dissolved atmospheric noble gases ranging between 1.4% ΔNe and 16.2% ΔNe was found. The measured noble gas patterns were interpreted using inverse modeling and conceptual gas exchange models and were compared to results of numerical simulations of gas bubble dissolution in water filled soil columns. The gas composition in most of the samples resembles either unfractionated pure atmospheric excess air or is fractionated in accordance with closed-system equilibration between entrapped air and surrounding water. In addition to the amount of entrapped air, the hydrostatic pressure exerted on the entrapped air bubbles is the dominating parameter responsible for the total amount of dissolved air. The composition of the excess air component is controlled by the water flow regime, the bubble size distribution, the initially dissolved gas concentrations and the initially entrapped gas composition. 相似文献
7.
为研究伴随高坝泄水产生的总溶解气体(TDG)过饱和现象与水体中含沙量关系的问题,提出切实可行的减缓TDG过饱和影响的措施,通过实验的方法,对含沙水体中TDG过饱和的生成和释放进行了研究分析。结果表明:同样初始条件下,在含沙水体与清水中的TDG过饱和生成过程中,TDG过饱和度没有明显变化。在TDG释放过程中,含沙水体中TDG释放速率明显快于清水中TDG释放速率,据此提出可通过开启排沙孔等泄洪调度方式使泄流中悬沙含量增加,促使TDG沿程释放加快,降低其对鱼类的影响。 相似文献
8.
9.
The water balance for the Basin of the Valley of Mexico and implications for future water consumption 总被引：2，自引：0，他引：2
The Basin of the Valley of Mexico is a closed basin of 9600?km2, where average annual precipitation (1980–85) is 746?mm (226.7?m3/s). Calculated actual evapotranspiration is 72–79% of the precipitation. The surrounding mountain ranges of the Sierra de Las Cruces, Sierra Nevada, and Sierra Chichinautzin are the main recharge areas for the enclosed Basin, in decreasing order. Calculated recharge rate is a maximum of 19?m3/s in the Metropolitan Zone, whereas a recent estimate of the groundwater exploitation rate indicates that 51.35?m3/s is being withdrawn from the Basin aquifer systems, resulting in a deficit of more than 30?m3/s. Taking into account infiltration processes by leaking water-supply systems, the calculated deficit is reduced to 20.5?m3/s. Overexploitation of the natural aquifer systems is also indicated by an average annual decline of 1?m of the potentiometric levels of the shallow groundwater systems. Possible solutions include: (1) the use of surface runoff water (unused amount in 1995?:?17.6?m3/s) for consumption purposes, which is currently pumped to areas outside the Basin; (2) an increased number and capacity of treatment plants; (3) the renovation of the leaky water-distribution network; (4) the reinjection of treated water; and (5) possible exploitation of deep regional aquifer systems. 相似文献
10.
Andrew H. Manning 《Hydrogeology Journal》2011,19(2):379-397
Noble gas recharge temperatures (NGTs) and radiocarbon ages were determined for 43 groundwater samples collected in the eastern Espa?ola Basin, New Mexico (USA), to identify mountain-block recharge in waters <10 thousand years (ka) old and to evaluate possible changes in mountain-block recharge over the past ??35?ka. For Holocene samples from the southeastern area, NGTs are dominantly 2?C4° cooler than the measured water-table temperature near the mountain front. Computed minimum mountain-block recharge fractions are dominantly 0.2?C0.5, consistent with previous large mountain-block recharge estimates. NGTs do not display the distinct low during the last glacial maximum observed in other paleorecharge studies; samples recharged 15?C25?ka ago are on average only 1.3° cooler than Holocene samples. Instead, samples with the coldest NGTs were recharged 25?C35?ka ago. A proposed explanation is that higher precipitation rates during the last glacial maximum resulted in a lower mean recharge elevation for the basin, essentially buffering the effect of the lower mean annual air temperature and producing NGTs similar to the Holocene. In the period preceding the last glacial maximum, precipitation rates more like today??s resulted in Holocene-like mountain-block recharge fractions, producing a mean NGT ??5° cooler than the Holocene, as expected. 相似文献
11.
Stephan Klump Yama Tomonaga Wolfgang Kinzelbach Dieter M. Imboden 《Geochimica et cosmochimica acta》2007,71(6):1385-1397
Gas exchange between seepage water and soil air within the unsaturated and quasi-saturated zones is fundamentally different from gas exchange between water and gas across a free boundary layer, e.g., in lakes or rivers. In addition to the atmospheric equilibrium fraction, most groundwater samples contain an excess of dissolved atmospheric gases which is called “excess air”. Excess air in groundwater is not only of crucial importance for the interpretation of gaseous environmental tracer data, but also for other aspects of groundwater hydrology, e.g., for oxygen availability in bio-remediation and in connection with changes in transport dynamics caused by the presence of entrapped air bubbles. Whereas atmospheric solubility equilibrium is controlled mainly by local soil temperature, the excess air component is characterized by the (hydrostatic) pressure acting on entrapped air bubbles within the quasi-saturated zone. Here we present the results of preliminary field experiments in which we investigated gas exchange and excess air formation in natural porous media. The experimental data suggest that the formation of excess air depends significantly on soil properties and on infiltration mechanisms. Excess air was produced by the partial dissolution of entrapped air bubbles during a sprinkling experiment in fine-grained sediments, whereas similar experiments conducted in coarse sand and gravel did not lead to the formation of excess air in the infiltrating water. Furthermore, the experiments revealed that the noble gas temperatures determined from noble gases dissolved in seepage water at different depths are identical to the corresponding in situ soil temperatures. This finding is important for all applications of noble gases as a paleotemperature indicator in groundwater since these applications are always based on the assumption that the noble gas temperature is identical to the (past) soil temperature. 相似文献
12.
An assessment of the potential and impacts of winter water banking in the Sokh aquifer, Central Asia
The dynamics of artificial recharge of winter surface flows coupled with increased summer groundwater use for irrigation in the Sokh aquifer (Central Asia) have been investigated. Water release patterns from the giant Toktogul reservoir have changed, as priority is now given to hydropower generation in winter in Kyrgyzstan. Winter flows have increased and summer releases have declined, but the Syr Darya River cannot pass these larger winter flows and the excess is diverted to a natural depression, creating a 40?×?109m3 lake. A water balance study of all 18 aquifers feeding the Fergana Valley indicated the feasibility of winter groundwater recharge in storage created by summer abstraction. This modeling study examines the dynamics of the process in one aquifer over a 5-year period, with four scenarios: the current situation; increased groundwater abstraction of around 625 million (M) m3/year; groundwater abstraction with an artificial recharge of 144 Mm3/year, equivalent to the volume available in low flow years in the Sokh River; and with a larger artificial recharge of 268 Mm3/year, corresponding to high flow availability. Summer surface irrigation diversions can be reduced by up to 350 Mm3 and water table levels can be lowered. 相似文献
13.
Groundwater resources assessment using numerical model: A case study in low-lying coastal area 总被引：4，自引：3，他引：1
S. M. Praveena A. Z. Aris Ph.D. 《International Journal of Environmental Science and Technology》2010,7(1):135-146
The impacts of climate change and human pressure in groundwater have been greatest threats facing small islands. This paper represents a case study of groundwater responses towards the climate change and human pressures in Manukan Island Malaysia. SEAWAT-2000 was used for the simulations of groundwater response in study area. Simulations of six scenarios representing climate change and human pressures showed changes in hydraulic heads and chloride concentrations. Reduction in pumping rate and an increase in recharge rate can alter the bad effects of overdrafts in Manukan Island. In general, reduction in pumping rate and an increase in recharge rate are capable to restore and protect the groundwater resources in Manukan Island. Thus, for groundwater management options in Manukan Island, scenario 2 is capable to lessen the seawater intrusion into the aquifer and sustain water resources on a long-term basis. The selection of scenario 6 is the preeminent option during wet season. The output of this study provides a foundation which can be used in other small islands of similar hydrogeological condition for the purpose of groundwater resources protection. 相似文献
14.
Temperature, discharge, and stable isotope ratios of five karst springs in a mountainous area of Zigui County, Hubei Province, Central China, were analyzed. The purpose was to illustrate the heat exchanges linked to circulation depth in the exposed karst water systems through the development of a method for estimating heat input and heat flux during a rainstorm. Meteorological water in the study area conformed to a local meteoric water line (δD?=?8.37 δ18O?+?12.99) with a mean δ18O elevation gradient of ?4.0‰ km?1, which was used to estimate mean circulation depths of 209–686 m. The mean spring temperatures defined a vertical gradient of ?5.4 °C km?1, which resembled that of the stable atmosphere of the Earth, indicating that the thermal response patterns are mainly controlled by surface air temperature. Thermal convection after rainfall events dominated heat exchange between baseflow and recharge water, leading to a warmer and colder recharge during summer and winter, respectively, whereas thermal conduction dominated the heat exchange only between groundwater, surrounding geology, and the interface air under a condition of no rainfall, resulting in only small temperature variations of the baseflow. Successful application of the method for estimating heat exchange showed that the characteristics of shallow circulation, strong karstification, and well-developed epikarst readily allowed disruption of the thermal balance of the Yuquandong system, resulting in a poor heat regulation capacity, a larger variation of heat input, a lower mean heat flux, and lower baseflow temperatures compared to those of the Dayuquan system.
相似文献15.
The influence of faults in basin-fill deposits on land subsidence,Las Vegas Valley,Nevada, USA 总被引：1，自引：0，他引：1
Thomas J. Burbey 《Hydrogeology Journal》2002,10(5):525-538
The role of horizontal deformation caused by pumping of confined-aquifer systems is recognized as contributing to the development
of earth fissures in semiarid regions, including Las Vegas Valley, Nevada. In spite of stabilizing water levels, new earth
fissures continue to develop while existing ones continue to lengthen and widen near basin-fill faults. A three-dimensional
granular displacement model based on Biot's consolidation theory (Biot, MA, 1941, General theory of three-dimensional consolidation.
Jour. Applied Physics 12:155–164) has been used to evaluate the nature of displacement in the vicinity of two vertical faults.
The fault was simulated as (1) a low-permeability barrier to horizontal flow, (2) a gap or structural break in the medium,
but where groundwater flow is not obstructed, and (3) a combination of conditions (1) and (2). Results indicate that the low-permeability
barrier greatly enhances horizontal displacement. The fault plane also represents a location of significant differential vertical
subsidence. Large computed strains in the vicinity of the fault may suggest high potential for failure and the development
of earth fissures when the fault is assumed to have low permeability. Results using a combination of the two boundaries suggest
that potential fissure development may be great at or near the fault plane and that horizontal deformation is likely to play
a key role in this development.
Electronic Publication 相似文献
16.
物质平衡法是计算气藏地质储量、水侵量、补给气量的有效方法之一.具有补给气的异常高压有水凝析气藏是气藏开发中最复杂的类型之一, 兼具异常高压气藏、凝析气藏和补给气的边底水气藏的特性.综合考虑开发过程中的凝析油析出, 岩石、束缚水和凝析油弹性膨胀, 水相挥发, 凝析气相中水蒸气增多, 水溶气溢出, 边底水的推进及外来气补给等复杂物理现象, 根据物质平衡原理, 推导了具有补给气的异常高压有水凝析气藏物质平衡方程, 并运用相对海明距离及关联度理论, 以驱动指数均方差、比拟压力与采出程度偏差指数和综合目标函数为分析因素, 分析了各组合方案贴近程度及相似程度, 挑选最佳组合方案并确定出地质储量、补给气量及水侵量, 同时计算了水体倍数.实例计算表明: 中国西北某凝析气藏地质储量为66.80×108 m3, 如果忽略凝析油, 计算地质储量偏大, 误差高达91.77%, 其次是水侵、弹性膨胀和气侵的影响, 误差分别为75.75%、23.95%和12.87%, 而溢出水溶气为2.69%与水蒸气为1.65%, 影响较小, 但也不可忽略. 相似文献
17.
Jay Quade 《Quaternary Research》1986,26(3)
Five stratigraphic units and five soils of late Pleistocene to Holocene age crop out in dissected badlands on Corn Creek Flat, 30 km northwest of Las Vegas, Nevada, and at Tule Springs, nearer to Las Vegas. The record is dominantly fluvial but contains evidence of several moister, marsh-forming periods: the oldest (Unit B) dates perhaps to the middle Wisconsin, and the more widespread Unit D falls between 30,000 and 15,000 yr B.P. Unit D therefore correlates with pluvial maximum lacustrine deposits elsewhere in the Great Basin. Standing water was not of sufficient depth or extent during either period to form lake strandlines. Between 14,000 and 7200 yr B.P. (Unit E), standing surface water gradually decreased, a trend also apparent in Great Basin pluvial lake chronologies during the same period. Groundwater carbonate cementation and burrowing by cicadas (Cicadae) accompany the moist-phase units. After 7200 yr B.P., increased wind action, decreased biotic activity, and at least 25 m of water-table lowering accompanied widespread erosion of older fine-grained deposits. Based on pack-rat midden and pollen evidence, this coincides with major vegetation changes in the valley, from sagebrush-dominated steppe to lower Mohave desertscrub. 相似文献
18.
针对冀中平原深部地下热水资源可更新性问题,以辛集馆陶组地下热水系统为例,采用相同开采强度下地下热水位降幅异常变化的识别方法,通过2000年以来该地下热水位年际及月际降幅与开采量和上游山区年降水量之间响应变化特征研究,结果表明:(1)冀中平原辛集地区馆陶组地下热水资源具有一定的可更新能力,与上游山区年降水量变化相关,还与地下水位埋深、当年开采引起的水位降幅大小和开采疏干层位砾粗砂岩及细砂岩占比状况有关;(2)辛集地区馆陶组地下热水大规模开采,是该地下水系统获得上游区侧向流入补给的必要条件,属于开采激发型补给,更新补给的资源数量有限;(3)从2000年以来该区地下热水水位动态变化趋势来看,目前该区地下热水资源已处于超采状态,需要压采或人工回灌增大补给,否则难以可持续开发利用。 相似文献
19.
通过建立地下水地源热泵系统试验场,运行热泵系统,并进行地下水温度连续监测,分析应用地下水地源热泵系统对地温场的影响。抽水井与回灌井之间以及回灌井附近的地下水温度随系统运行明显变化。系统运行后,回灌水体将以不规则边缘的透镜体贮存于含水层中,以回灌井为中心向外围扩展,水温最低或最高点位于含水层中部。粘性土相对隔水层的温度变化幅度、影响范围均小于含水层。由于热量的累积效应,即使是冷热负荷均衡的热泵系统,运行一个采暖、制冷周期后也将在热源井附近的抽、灌水含水层以及相邻的隔水层中形成冷量或热量的小范围聚积。 相似文献
20.
A. I. Calderhead R. Martel J. Garfias A. Rivera R. Therrien 《Environmental Earth Sciences》2012,66(7):1753-1767
A methodology is proposed to improve the groundwater budget model by determining the past, present, and future recharge and discharge rates. The model is applied to an increasingly urbanized and industrialized region with drying tendencies: the Toluca Valley, Mexico. This study includes spatially variable recharge determined from the historical climate data, the climate change predictions, and the multiple parameters used in the Hydrologic Evaluation of Landfill Performance (HELP3) model. Using HELP3 a spatial discretization for the average recharge is obtained and estimated at 376 million cubic meters per year (Mm3/year). When considering climate change predictions, by 2050 the average scenario projects recharge to decrease by 15 Mm3/year (from 376 to 361 Mm3/year), and in a worst case scenario up to a maximum decrease of 88 Mm3/year (from 376 to 288 Mm3/year). Groundwater pumping has increased steadily since 1970 and is estimated at 495 Mm3/year for 2010. The current average deficit estimated for 2010 is 172 Mm3/year with average projections increasing to over 292 Mm3/year by 2050. This study of two of the most important components of the water cycle (recharge and discharge) clearly shows that the decreasing water availability in the Toluca basin is due mainly to groundwater pumping and that the current pumping rates are not sustainable. The current deficit can be considered problematic and projections based on expected water consumption and climate change reinforce the need for management of the water resources to be addressed. 相似文献