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1.
Ground water budget analysis in arid basins is substantially aided by integrated use of numerical models and environmental isotopes. Spatial variability of recharge, storage of water of both modern and pluvial age, and complex three-dimensional flow processes in these basins provide challenges to the development of a good conceptual model. Ground water age dating and mixing analysis with isotopic tracers complement standard hydrogeologic data that are collected and processed as an initial step in the development and calibration of a numerical model. Environmental isotopes can confirm or refute a priori assumptions of ground water flow, such as the general assumption that natural recharge occurs primarily along mountains and mountain fronts. Isotopes also serve as powerful tools during postaudits of numerical models. Ground water models provide a means of developing ground water budgets for entire model domains or for smaller regions within the model domain. These ground water budgets can be used to evaluate the impacts of pumping and estimate the magnitude of capture in the form of induced recharge from streams, as well as quantify storage changes within the system. The coupled analyses of ground water budget analysis and isotope sampling and analysis provide a means to confirm, refute, or modify conceptual models of ground water flow. 相似文献
2.
International borders, ground water flow, and hydroschizophrenia 总被引：1，自引：0，他引：1
A substantial body of research has been conducted on transboundary water, transboundary water law, and the mitigation of transboundary water conflict. However, most of this work has focused primarily on surface water supplies. While it is well understood that aquifers cross international boundaries and that the base flow of international river systems is often derived in part from ground water, transboundary ground water and surface water systems are usually managed under different regimes, resulting in what has been described as "hydroschizophrenia." Adding to the problem, the hydrologic relationships between surface and ground water supplies are only known at a reconnaissance level in even the most studied international basins, and thus even basic questions regarding the territorial sovereignty of ground water resources often remain unaddressed or even unasked. Despite the tensions inherent in the international setting, riparian nations have shown tremendous creativity in approaching regional development, often through preventive diplomacy, and the creation of "baskets of benefits," which allow for positive-sum, integrative allocations of joint gains. In contrast to the notion of imminent water wars, the history of hydropolitical relations worldwide has been overwhelmingly cooperative. Limited ground water management in the international arena, coupled with the fact that few states or countries regulate the use of ground water, begs the question: will international borders serve as boundaries for increased "flows" of hydrologic information and communication to maintain strategic aquifers, or will increased competition for shared ground water resources lead to the potential loss of strategic aquifers and "no flows" for both ground water users? 相似文献
3.
Calculation of ground water ages--a comparative analysis 总被引：1，自引：0，他引：1
Ground water age is a fundamental, yet complex, concept in ground water hydrology. Discrepancies between results obtained through different modeling approaches for ground water age calculation have been reported, in particular, between ground water ages modeled by advection and direct simulation of ground water ages (e.g., age-mass approach), which includes effects of advection and dispersion. Here, through a series of two-dimensional (2D) simulations, the impact of water mixing through advection and dispersion on modeled 14C and directly simulated ground water ages is assessed. Impact of dispersion on modeled ages is systematically stronger in areas where water velocities are smaller and far more pronounced on 14C ages. This effect is also observed in one-dimensional models. 2D simulations show that longitudinal dispersion generally acts as a "source" of 14C, while vertical dispersion acts as a "sink," leading to apparent younger or older modeled 14C ages as compared to advective and directly simulated ground water ages. The presence of permeable and impermeable faults provides an equally important source for discrepancies, leading to major differences in modeled ages among the three methods considered. Overall, our results show that a 14C modeling approach using a solute transport model for calculating ground water age appears to be more reliable in ground water systems without faults and where water velocities are relatively high than in systems that are relatively more heterogeneous and those where faults are present. Among the three modeling approaches considered here, direct simulation of ground water age seems to yield the most consistent results in complex, heterogeneous ground water flow systems, giving a vertical age structure consistent with ages expected from consideration of the flow system. 相似文献
4.
Ground water discharge and nitrate flux to the Gulf of Mexico 总被引：3，自引：0，他引：3
Ground water samples (37 to 186 m depth) from Baldwin County, Alabama, are used to define the hydrogeology of Gulf coastal aquifers and calculate the subsurface discharge of nutrients to the Gulf of Mexico. The ground water flow and nitrate flux have been determined by linking ground water concentrations to 3H/3He and 4He age dates. The middle aquifer (A2) is an active flow system characterized by postnuclear tritium levels, moderate vertical velocities, and high nitrate concentrations. Ground water discharge could be an unaccounted source for nutrients in the coastal oceans. The aquifers annually discharge 1.1 +/- 0.01 x 10(8) moles of nitrate to the Gulf of Mexico, or 50% and 0.8% of the annual contributions from the Mobile-Alabama River System and the Mississippi River System, respectively. In southern Baldwin County, south of Loxley, increasing reliance on ground water in the deeper A3 aquifer requires accurate estimates of safe ground water withdrawal. This aquifer, partially confined by Pliocene clay above and Pensacola Clay below, is tritium dead and contains elevated 4He concentrations with no nitrate and estimated ground water ages from 100 to 7000 years. The isotopic composition and concentration of natural gas diffusing from the Pensacola Clay into the A3 aquifer aids in defining the deep ground water discharge. The highest 4He and CH4 concentrations are found only in the deepest sample (Gulf State Park), indicating that ground water flow into the Gulf of Mexico suppresses the natural gas plume. Using the shape of the CH4-He plume and the accumulation of 4He rate (2.2 +/- 0.8 microcc/kg/1000 years), we estimate the natural submarine discharge and the replenishment rate for the A3 aquifer. 相似文献
5.
Dry playa lakes and sabkhat often represent the terminus of large ground water flow systems and act as integrators of both upgradient (recharge) and downgradient discharge (evaporation). Ground water levels beneath playa/sabkha systems show a variety of surprising responses driven by large evaporation demands and chemical processes not typically encountered in more humid regions. When the water table is very close to the land surface, almost instantaneous rises can be observed with little observed change in either upgradient ground water recharge or potential evaporation. Conversely, when water tables are several meters below the playa surface, water table responses to interannual variability of recharge can be damped and lag significantly behind such changes. This review of the dynamics of shallow water tables in playa lakes and sabkhat discusses the pertinent hydraulic and solute processes and extracts a simple but comprehensive model based on soil physics for predicting the water table response to either upstream recharge changes or changes in potential evaporation at the playa/sabkha. Solutes and associated authigenic minerals are also shown to be important in discriminating both the causes and effects of water level fluctuations. 相似文献
6.
This study investigates the effectiveness of direct current electrical resistivity as a tool for assessing ground water/surface water interactions within streams. This research has shown that patterns of ground water discharge can be mapped at the meter scale, which is important for understanding stream water quality and ecosystem function. Underwater electrical resistivity surveys along a 107-m stream section within the Burd Run Watershed in South Central Pennsylvania identified three resistivity layers: a resistive (100 to 400 Ωm) surface layer corresponding to the streambed sediments, a conductive (20 to 100 Ωm) middle layer corresponding to residual clay sediments, and a resistive (100 to 450 Ωm) bottom layer corresponding to the carbonate bedrock. Tile probing to determine the depth to the bedrock and resistivity test box analysis of augered sediment samples confirmed these interpretations of the resistivity data. Ground water seeps occurred where the resistivity data showed that the residual clays were thinnest and bedrock was closest to the streambed. Plotting the difference in resistivity between two surveys, one conducted during low-stage and the other during high-stage stream conditions, showed changes in the conductivity of the pore fluids saturating the sediments. Under high-stream stage conditions, the top layer showed increased resistivity values for sections with surface water infiltration but showed nearly constant resistivity in sections with ground water seeps. This was expressed as difference values less than 50 Ωm in the area of the seeps and greater than 50 Ωm change for the streambed sediments saturated by surface water. Thus, electrical resistivity aided in characterizing ground water discharge zones by detecting variations in subsurface resistivity under high- and low-stream stage conditions as well as mapping subsurface heterogeneities that promote these exchanges. 相似文献
7.
Models for ground water flow (MODFLOW) and particle tracking (MODPATH) were used to determine ground water flow patterns, principal ground water discharge and recharge zones, and estimates of ground water travel times in an unconfined ground water system of an outer coastal plain watershed on the Delmarva Peninsula, Virginia. By coupling recharge and discharge zones within the watershed, flowpath analysis can provide a method to locate and implement specific management strategies within a watershed to reduce ground water nitrogen loading to surface water. A monitoring well network was installed in Eyreville Creek watershed, a first-order creek, to determine hydraulic conductivities and spatial and temporal variations in hydraulic heads for use in model calibration. Ground water flow patterns indicated the convergence of flow along the four surface water features of the watershed; primary discharge areas were in the nontidal portions of the watershed. Ground water recharge zones corresponded to the surface water features with minimal development of a regional ground water system. Predicted ground water velocities varied between < 0.01 to 0.24 m/day, with elevated values associated with discharge areas and areas of convergence along surface water features. Some ground water residence times exceeded 100 years, although average residence times ranged between 16 and 21 years; approximately 95% of the ground water resource would reflect land use activities within the last 50 years. 相似文献
8.
Ground water plays an important role in water supply and the ecology of arid to semiarid areas such as Northwest China, where the landscape is fragile due to frequent drought in the past few decades. This paper discusses the role of ground water in these ecosystems, including the effect of condensation water and water table depth on the growth of plants and degree of soil salinity. The paper also discusses the controlling process for land desertification and soil salinization in Northwest China. Water table depth is a key factor controlling the water balance, ground water flow, and salt transport in the vadose zone. The suitable water table depth for vegetation growth, which can prevent land desertification and soil salinization, is within a range of 2 to 4 m; the optimal depth is approximately 3 m. As examples, changes in ecosystems owing to water resources development in Tarim and Manas basins, Xinjiang, China, are discussed. 相似文献
9.
Ground water discharge to the Great Lakes around the Lower Peninsula of Michigan is primarily from recharge in riparian basins and proximal upland areas that are especially important to the northern half of the Lake Michigan shoreline. A steady-state finite-difference model was developed to simulate ground water flow in four regional aquifers in Michigan's Lower Peninsula: the Glaciofluvial, Saginaw, Parma-Bayport, and Marshall aquifers interlayered with the Till/"red beds," Saginaw, and Michigan confining units, respectively. The model domain was laterally bound by a continuous specified-head boundary, formed from lakes Michigan, Huron, St. Clair, and Erie, with the St. Clair and Detroit River connecting channels. The model was developed to quantify regional ground water flow in the aquifer systems using independently determined recharge estimates. According to the flow model, local stream stages and discharges account for 95% of the overall model water budget; only 50% enters the lakes directly from the ground water system. Direct ground water discharge to the Great Lakes' shorelines was calculated at 36 m3/sec, accounting for 5% of the overall model water budget. Lowland areas contribute far less ground water discharge to the Great Lakes than upland areas. The model indicates that Saginaw Bay receives only approximately 1.13 m3/sec ground water; the southern half of the Lake Michigan shoreline receives only approximately 2.83 m3/sec. In contrast, the northern half of the Lake Michigan shoreline receives more than 17 m3/sec from upland areas. 相似文献
10.
Edgar M. Smith 《Ground water》1978,16(5):352-353
Abstract. The uses of water for nuclear power plants consist of the following: service water, emergency cooling water, domestic (potable, sanitary), construction, and fire fighting. The quantity of water for these various uses may range from 10 gpm (0.63 1/s) for domestic supplies to greater than 100,000 gpm (6309 1/s) for service water and emergency cooling water supplies. Historically, the source of water for nuclear power plant use has been surface-water bodies, such as rivers, lakes, oceans, and man-made canals. Ground-water sources have supplied relatively small quantities of water for plant use, mainly domestic and construction supplies. A survey of 123 nuclear power plant sites which are either built, under construction, or planned, revealed that about 3 percent of all plant water supplies is derived from ground-water sources. Presently, four nuclear power plants intend to use ground water in relatively large quantities (as service water and emergency cooling water). Two of these plants will use ground water via induced infiltration from radial collector wells, and the other two plants intend to withdraw ground water from deep wells (1,000 feet) from a confined aquifer. Another plant, under construction, intends to use sewage effluent which is originally derived from a combination of surface and ground water. 相似文献
11.
Ground water is a vital, but underappreciated, natural resource in the Great Lakes basin. It meets many human needs and contributes significantly to the hydrology of the Great Lakes and the health of ecosystems. This paper provides an overview of ground water in the Great Lakes and the institutional and legal setting that governs the use, protection, diversion, and removal of water from the basin and proposes a citizen-centered vision for management of ground water in the 21st century. 相似文献
12.
The water budget myth revisited: why hydrogeologists model 总被引：26，自引：0，他引：26
Bredehoeft JD 《Ground water》2002,40(4):340-345
Within the ground water community, the idea persists that if one can estimate the recharge to a ground water system, one then can determine the size of a sustainable development. Theis addressed this idea in 1940 and showed it to be wrong-yet the myth continues. The size of a sustainable ground water development usually depends on how much of the discharge from the system can be "captured" by the development. Capture is independent of the recharge; it depends on the dynamic response of the aquifer system to the development. Ground water models were created to study the response dynamics of ground water systems; it is one of the principal reasons hydrogeologists model. 相似文献
13.
目前,我国湖泊富营养化及蓝藻水华问题十分突出,国家高度重视湖泊的生态环境保护.自“九五”以来,国家就投入太湖、巢湖、滇池“老三湖”等重污染湖泊的治理,但成本巨大,且历经近30年才初见成效.按照湖泊污染程度,湖泊治理与保护可分为“污染治理型”“防治结合型”“生态保育型”3大类.“老三湖”的治理是典型的“先污染、后治理”的模式,水质较好湖泊主要属于生态保育型湖泊,因此,“老三湖”治理模式不适用于水质较好湖泊的保护.本文系统总结了我国水质较好湖泊优先保护理念的形成和水质较好湖泊专项实施的历程.根据水质较好湖泊的特点,及其生态系统退化与修复的一般过程,提出了水质较好湖泊保护的基本思路.从热力学角度,阐明了氮磷营养盐输入湖泊生态系统中是熵增过程,也是湖泊生态系统退化的根本原因,湖泊氮磷污染负荷源头控制是关键.湖泊流域生态安全格局是确保湖泊生态系统健康的基础,从景观生态学角度,阐明了优化湖泊流域水土资源利用、优化发展模式是减轻湖泊环境压力的重要途径.在浅水湖泊生态系统,以沉水植物占优势的“清水态”和以浮游植物占优势的“浊水态”转换过程不是沿着同一条途径,存在上临界阈值和下临界阈值,水生态修复过程表现出一种迟滞的现象.从湖泊水生态系统稳态转换理论角度,阐明了湖泊生态修复工程应在湖泊生态系统发生退化转变之前实施,才能获得较高的环境效益.通过国家财政专项对81个水质较好湖泊的支持,既能促进湖泊流域经济社会发展,又能确保湖泊水环境质量变好,湖泊水生态系统逐步改善.建议加强不同类型湖泊保护模式的总结,深入对水质较好湖泊生态系统演替理论和保护技术研究,支撑国家系统开展水质较好湖泊保护. 相似文献
14.
利用瞬变电磁（TEM）和地面电磁（GEM）方法,本文研究了埃及Hawara遗址区的地下水对遗址的影响.这个遗址包括Hawara金字塔、北区墓地、以及被称作“迷宫”的南区墓葬场所.现今Hawara遗址已经完全荒废,被耕作区和Bahr Wahba运河包围.地表水和地下水会破坏Hawara金字塔和“迷宫”遗址的地基,现在金字塔入口已被淹没至地面下约6 m深处.本文在耕作区、金字塔以及“迷宫”等三个地区进行了TEM勘察;在“迷宫”地区进行了GEM勘察.综合分析以上两种勘察数据,我们发现,农业灌溉是浸入到地下的水的主要来源;本地区地下水位随着观测点及海拔的不同,在地面以下2~7 m之间变化. 相似文献
15.
Karst regions of the world are characterized by limestones and other soluble rocks at or near land surface that have been modified by solutional erosion. Such surface features as sinks, long dry valleys, sparse streams, and bare rock and such subsurface features as caverns, arterial solution openings leading to large springs, and a deep water table are typical of karst terranes. These features result in an uneven distribution of permeability in karst systems and surface and subsurface hydrologic conditions that require special hydrogeologic studies. Local high permeability at shallow depth in mature karst regions leads to an ecology associated with a soilless and water-scarce surface environment. Many practical problems result from this high permeability, including: (1) scarcity and poor predictability of groundwater supplies; (2) scarcity of surface-water supplies; (3) instability of the ground; (4) leakage of surface reservoirs; and (5) an unreliable waste-disposal environment.Interest in karst hydrology has increased greatly in the past decade; this interest has resulted in the international exchange of numerous published reports on local areas and on special topical karst problems. Many of these reports have been used by the authors in preparing this paper, which synthesizes results of many workers and focuses attention on: (1) the development of karst features through hydrologic processes; and (2) hydrologic systems of karst terranes. 相似文献
16.
David R. Geist Mark C. Joy David R. Lee Tom Gonser 《Ground Water Monitoring & Remediation》1998,18(1):78-82
An impact drive point method is described for emplacing piezometers in a cobble river bottom where this has previously been difficult without the use of drilling rigs. To force the drive point piezometers through coble, the vibrational impact of an air-powered hammer was carried directly to the drive point by the use of an internal drive rod. After insertion to depth, the drive rod was removed from the lower portion of the piezometer and a standpipe was added to extend the piezometer above the river level. Piezometers installed in this way have permitted water quality analysis and dynamic measurement of vertical potentials in cobble sediments ranging in size from 2.5 to >30 cm and the method has been successfully used in the Columbia River, USA, and Töss River, Switzerland. This innovative method provides information on the hydrodynamics of pore water in highly permeable, cobble deposits that are common in high-energy river and lake bottoms. Piezometers installed using the internal drive rod method facilitate the assessment of the temporal and spatial dynamics of recharge and discharge at the ground water/surface water interface and analyses of the ecological connectivity between the hyporheic zone and surface water of rivers and streams. This information will lead to improved management decisions related to our nation's ground water and surface water supplies. 相似文献
17.
ABSTRACTUnderstanding of the effect of basin water resources utilization on lake nutrients is helpful to prevent lake eutrophication and facilitate sustainable water resources management. In this study, a lake basin dualistic water cycle system is established to identify the environmental effect of lake water. Four water utilization indicators were chosen to build a driving relationship with the lake nutrients. Three different trophic lakes in Yunnan Province, China – Dianchi, Erhai and Fuxian – were selected to demonstrate the changes in basin water utilization, runoff, nutrient loads and water-use indicators for the period 2000–2015. In addition, the driving forces of water-use indicators to nutrients (total nitrogen and total phosphorus) were analysed by a general additive model. Finally, an optimized water utilization system for each lake basin is proposed. The research provides a practical tool for water resources and environmental management in lake basins. 相似文献
18.
Nutrient fluxes across terrestrial-aquatic boundaries and their subsequent integration into lake nutrient cycles are currently
a major topic of aquatic research. Although pollen represents a good substrate for microorganisms, it has been neglected as
a terrestrial source of organic matter in lakes. In laboratory experiments, we incubated pollen grains of Pinus sylvestris in water of lakes with different trophy and pH to estimate effects of pollen input and its subsequent microbial degradation
on nutrient dynamics. In this ex situ experiment, we measured concentrations of organic carbon, phosphorus and nitrogen in the surrounding water as well as microbial
dynamics (bacteria and fungal sporangia) at well-controlled conditions. Besides leaching, chemical and microbial decomposition
of pollen was strongest within the first week of incubation. This led to a marked increase of soluble reactive phosphorus
and total dissolved nitrogen (up to 0.04 and 1.5 mg L−1, respectively, after 5 days of incubation) in the ambient water. In parallel, pollen grains were rapidly colonized by heterotrophic
bacteria and aquatic fungi. Leaching and microbial degradation of pollen accounted for ≥80, ≥40, ≥50% for organic C, N and
P, respectively, and did not significantly differ among water samples from the studied lakes. Thus, pollen introduces high
amounts of bio-available terrestrial organic matter and nutrients into surface waters within a short time. A rough calculation
on P input into oligotrophic Lake Stechlin indicates that pollen plays an important ecological role in nutrient cycling of
temperate lakes. This requires further attention in aquatic ecology. 相似文献
19.
Joshua C. Koch 《水文研究》2016,30(21):3918-3931
Arctic thaw lakes are an important source of water for aquatic ecosystems, wildlife, and humans. Many recent studies have observed changes in Arctic surface waters related to climate warming and permafrost thaw; however, explaining the trends and predicting future responses to warming is difficult without a stronger fundamental understanding of Arctic lake water budgets. By measuring and simulating surface and subsurface hydrologic fluxes, this work quantified the water budgets of three lakes with varying levels of seasonal drainage, and tested the hypothesis that lateral and subsurface flows are a major component of the post‐snowmelt water budgets. A water budget focused only on post‐snowmelt surface water fluxes (stream discharge, precipitation, and evaporation) could not close the budget for two of three lakes, even when uncertainty in input parameters was rigorously considered using a Monte Carlo approach. The water budgets indicated large, positive residuals, consistent with up to 70% of mid‐summer inflows entering lakes from lateral fluxes. Lateral inflows and outflows were simulated based on three processes; supra‐permafrost subsurface inflows from basin‐edge polygonal ground, and exchange between seasonally drained lakes and their drained margins through runoff and evapotranspiration. Measurements and simulations indicate that rapid subsurface flow through highly conductive flowpaths in the polygonal ground can explain the majority of the inflow. Drained lakes were hydrologically connected to marshy areas on the lake margins, receiving water from runoff following precipitation and losing up to 38% of lake efflux to drained margin evapotranspiration. Lateral fluxes can be a major part of Arctic thaw lake water budgets and a major control on summertime lake water levels. Incorporating these dynamics into models will improve our ability to predict lake volume changes, solute fluxes, and habitat availability in the changing Arctic. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
20.
This paper is a review of research works concerning the nutrient transportation, transformation and exchange between water, sediment and biota in the lakes from the middle and lower reaches of the Yangtze River conducted in the context of project entitled "The Processes and Mechanism of Lake Eutrophication in Middle and Lower Reaches of Yangtze River". All the lakes from this area are shallow lakes. According to the typical lake site research, the lakes from the middle and lower reaches of Yangtze River have a higher baseline of nutrition in the history. Normally the trophic status of these lakes can be categorized into medium-trophic or eutrophic. Human activities have been enhanced during the last decades, which speed up the lake eutrophic process. Lake eutrophication control needs to reduce not only the external nutrient inputs from watershed but also the internal loading from the sediments. Investigations revealed that the lake sediments in this area are considerablly high in nutrition in which at most about 30% of phosphorus exists in the form of bio-available in the sediment. The surface sediment will exert great effects on the nutrient exchange between water-sediment interface via adsorption and release of nutrient. The nutrient release from the sediment in these shallow lakes is mainly in two ways, i.e. in the undisturbed condition the nutrient is released through diffusion created by the nutrient gradient from sediment to overlying water; whereas in disturbed condition, the nutrient release is determined by the hydrodynamic forcing intensity and the sediment resuspension. Metallic elements such as the iron, manganese and aluminium and the aerobic-anaerobic ambience will affect the release of nutrients. The disturbed release will increase the total nutrients in the water column significantly in the short period. At the beginning of sediment resuspension, the dissolved nutrient concentration will increase. This increase will be damped if the ferric oxide and aluminium are rich in sediment because of the adsorption and flocculation. This means that the lakes have capability of eliminating the nutrient loadings. Investigations for the lakes from middle and down stream of Yangtze River have suggested that most lakes have the self-cleaning capability. Dredging the control of the internal loading, therefore, is only applicable to the small lakes or undisturbed bays which normally are situated nearby the city or town and rich in organic materials in the sediment. In addition, the strong reduction condition and weak aeration of these lakes and bays make these small lakes and bays release much more bio-available nutrient and without much self-eliminating capability. Moreover, eutrophication induced algal bloom in these lakes will change the pH of water, which further induces the increase in the nutrient release. In turn, the increase in nutrient release promotes the growth of phytoplankton and results in severe algal bloom. For the heavily polluted water, research suggests that the biomass of bacteria and alkaline phosphatase activity will be higher corresponding to the higher concentration of nutrients, which accelerates the nutrient recycling between water, sediment and biota. Quick recycling of nutrient, in turn, promotes the production and biomass growth of microorganism and leads to more severe eutrophication. Further research work should focus on the nutrient transformation mechanism and the effects of microbial loop on the eutrophication. 相似文献