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1.
Nadeau S. Rosa E. Cloutier V. Mayappo D. Paran F. Graillot D. 《Hydrogeology Journal》2021,29(6):2053-2075
This study focuses on the development of two GIS-based approaches that are used jointly to evaluate the groundwater resources associated with granular aquifers in shield environments. The first approach is a multi-criteria analysis (MCA) using an analytical hierarchic process (AHP) based on geological and hydrogeological data for ranking the probability of finding readily available groundwater resources in a specific territory. The second approach relies on GIS-based geometric calculations that were developed for evaluating the extent and volume of aquifers. The approaches are applied on a 100?×?100 m grid in a 185,000-km2 area corresponding to watersheds of the James Bay area in Quebec, Canada. The MCA-AHP approach revealed that the unconfined granular aquifers that present the highest aquifer potential (AP) are sparsely distributed and mostly associated with glaciofluvial formations such as the Harricana and Sakami moraines. The geometric calculations approach allowed for estimating that the total volume of groundwater stored in the unconfined granular aquifers reaches approximately 40 km3. When used jointly, the two approaches reveal that the shallow unconfined aquifers that require increased groundwater protection account for approximately 5% of the territory. In areas of confined granular aquifers, the highest APs are located in river valleys and lowlands. A sensitivity analysis conducted on the MCA-AHP approach revealed that the grid size does not significantly affect the results. Therefore, the approach was expanded northward, to a 490,000-km2 territory reaching the Ungava Bay area. The proposed method could be adapted and applied in other shield areas.
相似文献2.
地下水资源在中国社会经济发展中发挥重要作用,特别是在地表水资源相对匮乏的北方地区。掌握一个地区地下水资源状况、动态变化特征及可开采潜力,对该地区的供水安全保障至关重要。本文选择雄安新区,在近年来开展的区域水文地质调查、监测及综合研究等成果基础上,结合前人研究,对雄安新区区域水文地质条件、地下水动态变化特征等进行分析总结;以恢复地下水降落漏斗为地下水可持续开采利用方案的目标,从白洋淀流域平原区尺度,设置现状开采条件、河流补水、工农业节水及地下水禁(限)采等不同情景方案,采用地下水数值模拟技术,综合分析不同情景30年后的预测结果,提出白洋淀流域平原区地下水可持续开采利用方案;在流域地下水可持续开采利用方案基础上,分析雄安新区地下水可开采的最大资源量,进而评价雄安新区地下水可开采潜力。结果显示,雄安新区区域水文地质条件相对简单,浅层富水性中等,深层富水性较强;地下水位为多年下降状态,近年来,浅、深层地下水整体呈企稳或回升状态,局部地区仍有所下降;地下水质量总体良好,且较为稳定。根据评价结果,雄安新区地下水可开采潜力约为1.80×10~8m~3/a,其中,浅层地下水可开采潜力约为1.50×10~8m~3/a,深层地下水可开采潜力约为0.30×10~8m~3/a。 相似文献
3.
Unplugged abandoned oil and gas wells in the Appalachian region can serve as conduits for the movement of waters impacted by fossil fuel extraction. Strontium isotope and geochemical analysis indicate that artesian discharges of water with high total dissolved solids (TDS) from a series of gas wells in western Pennsylvania result from the infiltration of acidic, low Fe (Fe < 10 mg/L) coal mine drainage (AMD) into shallow, siderite (iron carbonate)-cemented sandstone aquifers. The acidity from the AMD promotes dissolution of the carbonate, and metal- and sulfate-contaminated waters rise to the surface through compromised abandoned gas well casings. Strontium isotope mixing models suggest that neither upward migration of oil and gas brines from Devonian reservoirs associated with the wells nor dissolution of abundant nodular siderite present in the mine spoil through which recharge water percolates contribute significantly to the artesian gas well discharges. Natural Sr isotope composition can be a sensitive tool in the characterization of complex groundwater interactions and can be used to distinguish between inputs from deep and shallow contamination sources, as well as between groundwater and mineralogically similar but stratigraphically distinct rock units. This is of particular relevance to regions such as the Appalachian Basin, where a legacy of coal, oil and gas exploration is coupled with ongoing and future natural gas drilling into deep reservoirs. 相似文献
4.
5.
D. Karunanidhi G. Vennila M. Suresh P. Karthikeyan 《Arabian Journal of Geosciences》2014,7(5):1791-1798
The increasing demand for freshwater has necessitated the exploration for new sources of groundwater, particularly in hard rock terrain, where groundwater is a vital source of freshwater. A fast, cost effective, and economical way of exploration is to study and analyze geophysical resistivity survey data. The present study area Omalur taluk, Salem District, Tamil Nadu, India, is overlain by Archaean crystalline metamorphic complex. The study area is a characteristic region of unconfined aquifer system. The potential for occurrence of groundwater in the study areas was classified as very good, good, moderate, and poor by interpreting the subsurface geophysical investigations, namely vertical electrical soundings, were carried out to delineate potential water-bearing zones. The studies reveal that the groundwater potential of shallow aquifers is due to weathered zone very low resistivity and very high thickness and the potential of deeper aquifers is determined by fracture zone very low resistivity and very high thickness area. By using conventional GIS method, the spatial distribution maps for different layer (top soil, weathered zone, first fracture zone, and second fracture zone) thicknesses were prepared. The geoelectrical approach was successfully applied in the study area and can be therefore easily adopted for similar environments. 相似文献
6.
Managing transboundary groundwater resources requires accurate and detailed knowledge of aquifers and groundwater bodies. The Pannonian Basin is the largest intracontinental basin in Europe with a continuous succession of more than 7 km of Miocene to Quaternary sediments and with an average geothermal gradient of about 5 °C/100 m. Geographically the Pannonian basin overlaps eight countries (Hungary, Romania, Serbia, Croatia, Slovenia, Austria, Slovakia and Ukraine), so the issue of transboundary cold and thermal water resources is regionally very important. The T-JAM bilateral Hungarian–Slovenian (HU–SLO) project is the first to apply modern isotopic and chemical analyses in the characterization and correlation of a number of shared groundwater resources in the Mura-Zala Sub-basin of the Pannonian. The aims of this work were the identification of groundwater flow paths, the delineation of transboundary aquifers based on thermal and cold groundwater geochemical and isotope properties in the Mura-Zala Basin, and providing input to calibrate a hydraulic numerical model. Following a common groundwater sampling campaign, 24 cold and thermal groundwater samples from seven aquifers were collected for chemical, isotope, gas and noble gas analyses. Chemical analyses, and D, O and C isotopes were used to correlate cross border aquifers. A regional groundwater flow is hydrogeologically possible in some aquifers in the Mura-Zala Basin, and has been confirmed by hydrogeochemistry. The Újfalu (HU) and Mura (SLO) Formations are a part of the active regional thermal groundwater flow system, probably hydraulically separated from the shallower flow system of the Ptuj-Grad (SLO), Zagyva and Somló-Tihany (HU) Formations. The thermal water is of meteoric origin, reductive and alkaline. The predominant water type in the Quaternary and Pliocene aquifers is Ca–Mg–HCO3, changing to Na–HCO3 in the main Pannonian geothermal aquifer, and Na–Cl brine in deeper and older Miocene aquifers. Total dissolved solids and Na content generally increase with depth. Deuterium is in the range −87‰ to −75‰, 18O from −11.9‰ to −10.4‰, while 14C values are less than 6.1 pmC in the samples of the active regional thermal groundwater flow system. These and results of noble gas analyses indicate recharge during the Pleistocene interglacial period with temperatures around 6–7 °C. Regional thermal water resources are limited and environmental isotopes can be used as an early warning in the management of thermal water. 相似文献
7.
S. B. Singh B. Veeraiah R. L. Dhar B. A. Prakash M. Tulasi Rani 《Hydrogeology Journal》2011,19(2):355-366
Exploration and exploitation of groundwater in sedimentary areas are reasonably simple. However, the problem of salinity in coastal areas makes the job very difficult, especially when the freshwater aquifers are not extensive and are entrapped between saline aquifers. States along the eastern coast of India, particularly Orissa with respect to the Mahanadi basin, have acute problems with groundwater salinity. It has been possible to locate horizons of fresh groundwater entrapped between deep saline aquifers in the southwestern part of Mahanadi delta, with the help of deep resistivity soundings along the Delang-Puri profile. This finding has been validated through boreholes and checked with electrical logs of this region. Three freshwater aquifers have been detected: one at shallow depth between 20 and 60?m, the second in the depth range of 90??60?m, and the third in the fractured/weathered basement. The second freshwater aquifer has the most potential; it has a thickness range of 20??0?m and it could be exploited to overcome problematic salinity issues. In general, the depth to basement is variable and it increases seaward. 相似文献
8.
9.
Anuar Sefie Ahmad Zaharin Aris Mohammad Firuz Ramli Tahoora Sheikhy Narany Mohd Khairul Nizar Shamsuddin Syaiful Bahren Saadudin Munirah Abdul Zali 《Environmental Earth Sciences》2018,77(10):397
Continual expansion of population density, urbanization, agriculture, and industry in most parts of the world has increased the generation of pollution, which contributes to the deterioration of surface water quality. This causes the dependence on groundwater sources for their daily needs to accumulate day by day, which raises concerns about their quality and hydrogeochemistry. This study was carried out to increase understanding of the geological setup and assess the groundwater hydrogeochemical characteristics of the multilayered aquifers in Lower Kelantan Basin. Based on lithological data correlation of exploration wells, the study area can be divided into three main aquifers: shallow, intermediate and deep aquifers. From these three aquifers, 101 groundwater samples were collected and analyzed for various parameters. The results showed that pH values in the shallow, intermediate and deep aquifers were generally acidic to slightly alkaline. The sequences of major cations and anions were Na+ > Ca2+ > Mg2+ > K+ and HCO3? > Cl? > SO42? > CO32?, respectively. In the intermediate aquifer, the influence of ancient seawater was the primary factor that contributed to the elevated values of electrical conductivity (EC), Cl? and total dissolved solids (TDS). The main facies in the shallow aquifer were Ca–HCO3 and Na–HCO3 water types. The water types were dominated by Na–Cl and Na–HCO3 in the intermediate aquifer and by Na–HCO3 in the deep aquifer. The Gibbs diagram reveals that the majority of groundwater samples belonged to the deep aquifer and fell in the rock dominance zone. Shallow aquifer samples mostly fell in the rainfall zone, suggesting that this aquifer is affected by anthropogenic activities. In contrast, the results suggest that the deep aquifer is heavily influenced by natural processes. 相似文献
10.
The assessment of the environmental impacts of CO2 geological storage requires the investigation of potential CO2 leakages into fresh groundwater, particularly with respect to protected groundwater resources. The geochemical processes and perturbations associated with a CO2 leak into fresh groundwater could alter groundwater quality: indeed, some of the reacting minerals may contain hazardous constituents, which might be released into groundwater. Since the geochemical reactions may occult direct evidence of intruding CO2, it is necessary to characterize these processes and identify possible indirect indicators for monitoring CO2 intrusion. The present study focuses on open questions: Can changes in water quality provide evidence of CO2 leakage? Which parameters can be used to assess impact on freshwater aquifers? What is the time scale of water chemistry degradation in the presence of CO2? The results of an experimental approach allow selecting pertinent isotope tracers as possible indirect indicators of CO2 presence, opening the way to devise an isotopic tracing tool.The study area is located in the Paris Basin (France), which contains deep saline formations identified as targets by French national programs for CO2 geological storage. The study focuses on the multi-layered Albian fresh water aquifer, confined in the central part of the Paris Basin a major strategic potable groundwater overlying the potential CO2 storage formations. An experimental approach (batch reactors) was carried out in order to better understand the rock–water–CO2 interactions with two main objectives. The first was to assess the evolution of the formation water chemistry and mineralogy of the solid phase over time during the interaction. The second concerned the design of an isotopic monitoring program for freshwater resources potentially affected by CO2 leakage. The main focus was to select suitable environmental isotope tracers to track water rock interaction associated with small quantities of CO2 leaking into freshwater aquifers.In order to improve knowledge on the Albian aquifer, and to provide representative samples for the experiments, solid and fluid sampling campaigns were performed throughout the Paris Basin. Albian groundwater is anoxic with high concentrations of Fe, a pH around 7 and a mineral content of 0.3 g L−1. Macroscopic and microscopic solid analyses showed a quartz-rich sand with the presence of illite/smectite, microcline, apatite and glauconite. A water–mineral–CO2 interaction batch experiment was used to investigate the geochemical evolution of the groundwater and the potential release of hazardous trace elements. It was complemented by a multi-isotope approach including δ13CDIC and 87Sr/86Sr. Here the evolution of the concentrations of major and trace elements and isotopic ratios over batch durations from 1 day to 1 month are discussed. Three types of ion behavior are observed: Type I features Ca, SiO2, HCO3, F, PO4, Na, Al, B, Co, K, Li, Mg, Mn, Ni, Pb, Sr, Zn which increased after initial CO2 influx. Type II comprises Be and Fe declining at the start of CO2 injection. Then, type III groups element with no variation during the experiments like Cl and SO4. The results of the multi-isotope approach show significant changes in isotopic ratios with time. The contribution of isotope and chemical data helps in understanding geochemical processes involved in the system. The isotopic systems used in this study are potential indirect indicators of CO2–water–rock interaction and could serve as monitoring tools of CO2 leakage into an aquifer overlying deep saline formations used for C sequestration and storage. 相似文献
11.
Jerome Métral Laurent Charlet Sara Bureau Sukumar Basu Mallik Sudipta Chakraborty Kazi M Ahmed MW Rahman Zhongqi Cheng Alexander van Geen 《Geochemical transactions》2008,9(1):1
Background
The origin of the spatial variability of dissolved As concentrations in shallow aquifers of the Bengal Basin remains poorly understood. To address this, we compare here transects of simultaneously-collected groundwater and aquifer solids perpendicular to the banks of the Hooghly River in Chakdaha, India, and the Old Brahmaputra River in Araihazar, Bangladesh. 相似文献12.
Salinity mapping of coastal groundwater aquifers using hydrogeochemical and geophysical methods: a case study from north Kelantan,Malaysia 总被引：2，自引：0，他引：2
Integrated hydrogeochemical and geophysical methods were used to study the salinity of groundwater aquifers along the coastal
area of north Kelantan. For the hydrogeochemical investigation, analysis of major ion contents of the groundwater was conducted,
and other chemical parameters such as pH and total dissolved solids were also determined. For the geophysical study, both
geoelectrical resistivity soundings and reflection seismic surveys were conducted to determine the characteristics of the
subsurface and groundwater contained within the aquifers. The pH values range from 6.2 to 6.8, indicating that the groundwater
in the study area is slightly acidic. Low content of chloride suggests that the groundwater in the first aquifer is fresh,
with an average concentration of about 15.8 mg/l and high geoelectrical resistivity (>45 ohm m). On the other hand, the groundwater
in the second aquifer is brackish, with chloride concentration ranging from 500 mg/l to 3,600 mg/l and very low geoelectrical
resistivity (<45 ohm m) as well as high concentration of total dissolved solids (>1,000 mg/l). The groundwater in the third
aquifer is fresh, with chloride concentrations generally ranging from 2 mg/l to 210 mg/l and geoelectrical resistivity of
greater than 45 ohm m. Fresh and saltwater interface in the first aquifer is generally located directly in the area of the
coast, but, for the second aquifer, both hydrogeochemical and geoelectrical resistivity results indicate that the fresh water
and saltwater interface is located as far as 6 km from the beach. The considerable chloride ion content initially suggests
that the salinity of the groundwater in the second aquifer is probably caused by the intrusion of seawater. However, continuous
monitoring of the chloride content of the second aquifer indicated no significant changes with time, from which it can be
inferred that the salinity of the groundwater is not affected by seasonal seawater intrusion. Schoeller diagrams illustrate
that sulphate concentrations of the groundwater of the second aquifer are relatively low compared to those of the recent seawater.
Therefore, this result suggests that the brackish water in the second aquifer is probably from ancient seawater that was trapped
within the sediments for a long period of time, rather than due to direct seawater intrusion. 相似文献
13.
Erik Espinosa María Aurora Armienta Olivia Cruz Alejandra Aguayo Nora Ceniceros 《Environmental Geology》2009,58(7):1467-1477
High arsenic (As) groundwater is widely distributed in northwestern Hetao Plain, an arid region with sluggish groundwater
flow. Observed As concentration in groundwater from wells ranges from 76 to 1,093 μg/l. Most water samples have high total
dissolved solids, with Cl and HCO3 as the dominant anions and Na as the dominant cation. The major hydrochemical types of most saline groundwaters are Na–Mg–Cl–HCO3 and Na–Mg–Cl. By contrast, fresh groundwaters generally belong to the Na–Mg–HCO3 type. High concentrations of arsenic in shallow aquifers are associated with strongly reducing conditions, as evidenced by
high concentrations of dissolved organic carbon, ammonium, as well as dissolved sulfide and Fe, dominance of arsenite, relatively
low concentrations of nitrate and sulfate, and occasionally high content of dissolved methane (CH4). High As groundwaters from different places at Hetao Plain experienced different redox processes. Fluoride is also present
in high As groundwater, ranging between 0.40 and 3.36 mg/l. Although fluorosis poses an additional health problem in the region,
it does not correlate well with As in spatial distribution. Geochemical analysis indicates that evapotranspiration is an important
process controlling the enrichment of Na and Cl, as well as trace elements such as As, B, and Br in groundwater.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Simulation of chloride migration rates in Paleo Pennar Delta Region, Coastal Andhra Pradesh, India 总被引：1，自引：0，他引：1
Quaternary alluvial aquifers in the paleo Pennar delta region of Andhra Pradesh (Long. 80°0′ and 80°12′; Lat. 14°40′ and
14°20′) constitute an important coastal strip, with potential fresh groundwater resources and several well fields in operation.
The lineament patterns and traces of paleo channels provide basic information on the configuration and boundaries of paleo
delta and the possible neotectonic movements in the region. The paleo delta region is essentially characterized by freshwater
aquifer systems at the near-surface depths, (up to 50 m from ground level) with transmissivity values in the system ranging
from 1200 to 2500 m2/day. This groundwater system has been subjected to heavy draft situation over the last two decades, parlicularly near the
outer rim of the delta where an unlined brackish-water canal runs parallel to the coast imparting chloride contamination to
the adjoining fresh aquifers. A two-dimensional solute transport model solution was applied to assess chloride migration rates
inland under different hydraulic stresses, combining finite difference solution of flow equation and the method of characteristic
solution of solute transport equation. Groundwater flow and chloride migration patterns/rates were obtained for different
simulated stress events in the delta system, and measures required to protect the freshwater resources ara outlined.
Received: 2 January 1997 · Accepted: 4 November 1997 相似文献
15.
Yvonne S. Anku Bruce Banoeng-Yakubo Daniel K. Asiedu Sandow M. Yidana 《Environmental Geology》2009,58(5):989-997
Hydrochemical data are presented for groundwater samples, collected from fractured aquifers in parts of northern Ghana. The
data was collected to assess the groundwater suitability for domestic and agricultural use. Results of the study reveal that
the pH of the groundwater in the area is slightly acidic to slightly alkaline. The electrical conductivity values, total dissolved
solids (TDS) values and calcium, magnesium and sodium concentrations in the groundwater are generally below the limit set
by the WHO for potable water supply. On the basis of activity diagrams, groundwater from the fractured aquifers appears to
be stable within the montmorillonite field, suggesting weathering of silicate minerals. An inverse distance weighting interpolator
with a power of 2 was applied to the data points to produce prediction maps for nitrate and fluoride. The distribution maps
show the presence of high nitrate concentrations (50–194 mg/l) in some of the boreholes in the western part of the study area
indicating anthropogenic impact on the groundwater. Elevated fluoride level (1.5–4 mg/l), higher than the WHO allowable fluoride
concentration of 1.5, is recorded in the groundwater underlying the northeastern part of the study area, more specifically
Bongo and its surrounding communities of the Upper East region. Results of this study suggest that groundwater from the fractured
aquifers in the area exhibit low sodicity–low salinity (S1–C1), low sodicity–medium salinity (S1–C2) characteristics [United
States Salinity Laboratory (USSL) classification scheme]. All data points from this study plot within the ‘Excellent to good’
category on a Wilcox diagram. Groundwater in this area thus appears to provide irrigation water of excellent quality. The
hydrochemical results indicate that, although nitrate and fluoride concentrations in some boreholes are high, the groundwater
in the study area, based on the parameters analyzed, is chemically potable and suitable for domestic and agricultural purposes. 相似文献
16.
Three aquifer systems as deep, middle, and shallow were identified in the Kazan trona ore deposit area. The flow conditions
and the interaction between various layers were conceptualized into a site hydrogeological model. Each aquifer system was
hydraulically and chemically characterized and represented in a numerical groundwater model. The resulting model has been
calibrated under steady-state and transient conditions using available data. The flow model was used in conjunction with a
three-dimensional solute transport model to assess the impacts of the pilot well solution mining of the trona deposit on groundwater
resources during operation and post-operation periods. The results of operation period indicate that, even under the worse
conditions (50 times increase in vertical hydraulic conductivity due to subsidence), ion contribution from the mine area with
118,000 mg/l maximum concentration would be about 58 mg/l into the deep aquifer system. This contribution is about 1.45% of
the existing concentration (4,000 mg/l) in the deep aquifer. After 1,000 years of post-operation period, ion contribution
from the mine area with maximum 119,000 mg/l concentration would be about 205 mg/l into the deep aquifer under extremely worse
conditions. This contribution is about 5–20% of present concentrations in the deep aquifer. Retardation factors, which were
not considered during model simulations would decrease the predicted concentrations. It is concluded that pilot well solution
mining of the trona deposit would not have significant impact on the quality of groundwater resources in the overlying aquifers. 相似文献
17.
Groundwater recharge and evolution of water quality in China’s Jilantai Basin based on hydrogeochemical and isotopic evidence 总被引：1，自引：0，他引：1
Guoxiao Wei Fahu Chen Jinzhu Ma Yang Dong Gaofeng Zhu W. Mike Edmunds 《Environmental Earth Sciences》2014,72(9):3491-3506
We investigated major ions, stable isotopes, and radiocarbon dates in a Quaternary aquifer in semi-arid northwestern China to gain insights into groundwater recharge and evolution. Most deep and shallow groundwater in the Helan Mountains was fresh, with total dissolved solids <1,000 mg L?1 and Cl? <250 mg L?1. The relationships of major ions with Cl? suggest strong dissolution of evaporites. However, dissolution of carbonates, albite weathering, and ion exchange are also the major groundwater process in Jilantai basin. The shallow desert groundwater is enriched in δ18O and intercepts the local meteoric water line at δ18O = ?13.4 ‰, indicating that direct infiltration is a minor recharge source. The isotope compositions in intermediate confined aquifers resemble those of shallow unconfined groundwater, revealing that upward recharge from intermediate formations is a major source of shallow groundwater in the plains and desert. The estimated residence time of 10.0 kyr at one desert site, indicating that some replenishment of desert aquifers occurred in the late Pleistocene and early Holocene with a wetter and colder climate than at present. 相似文献
18.
The Quaternary coastal plain aquifer down gradient of the Wadi Watir catchment is the main source of potable groundwater in the arid region of south Sinai, Egypt. The scarcity of rainfall over the last decade, combined with high groundwater pumping rates, have resulted in water-quality degradation in the main well field and in wells along the coast. Understanding the sources of groundwater salinization and amount of average annual recharge is critical for developing sustainable groundwater management strategies for the long-term prevention of groundwater quality deterioration. A combination of geochemistry, conservative ions (Cl and Br), and isotopic tracers (87/86Sr, δ81Br, δ37Cl), in conjunction with groundwater modeling, is an effective method to assess and manage groundwater resources in the Wadi Watir delta aquifers. High groundwater salinity, including high Cl and Br concentrations, is recorded inland in the deep drilled wells located in the main well field and in wells along the coast. The range of Cl/Br ratios for shallow and deep groundwaters in the delta (∼50–97) fall between the end member values of the recharge water that comes from the up gradient watershed, and evaporated seawater of marine origin, which is significantly different than the ratio in modern seawater (228). The 87/86Sr and δ81Br isotopic values were higher in the recharge water (0.70,723 < 87/86Sr < 0.70,894, +0.94 < δ81Br < +1.28‰), and lower in the deep groundwater (0.70,698 < 87/86Sr < 0.70,705, +0.22‰ < δ81Br < +0.41‰). The δ37Cl isotopic values were lower in the recharge water (−0.48 < δ37Cl < −0.06‰) and higher in the deep groundwater (−0.01 < δ37Cl < +0.22‰). The isotopic values of strontium, chloride, and bromide in groundwater from the Wadi Watir delta aquifers indicate that the main groundwater recharge source comes from the up gradient catchment along the main stream channel entering the delta. The solute-weighted mass balance mixing models show that groundwater in the main well field contains 4–10% deep saline groundwater, and groundwater in some wells along the coast contain 2–6% seawater and 18–29% deep saline groundwater.A three-dimensional, variable-density, flow-and-transport SEAWAT model was developed using groundwater isotopes (87Sr/86Sr, δ37Cl and δ81Br) and calibrated using historical records of groundwater level and salinity. δ18O was used to normalize the evaporative effect on shallow groundwater salinity for model calibration. The model shows how groundwater salinity and hydrologic data can be used in SEAWAT to understand recharge mechanisms, estimate groundwater recharge rates, and simulate the upwelling of deep saline groundwater and seawater intrusion. The model indicates that most of the groundwater recharge occurs near the outlet of the main channel. Average annual recharge to delta alluvial aquifers for 1982 to 2009 is estimated to be 2.16 × 106 m3/yr. The main factors that control groundwater salinity are overpumping and recharge availability. 相似文献
19.
Incubation studies were carried out using 5 freshly collected sediments from shallow aquifers of the Hetao Basin, Inner Mongolia. The aquifer sediments covering a range of redox conditions, as indicated by their deep grey to yellow color were mixed with degassed artificial As solution or degassed deionized water at a ratio of solid to water of about 1:10 (wt./wt.). Suspensions which were either amended with glucose or autoclaved, were incubated in parallel with unamended suspensions. Five microcosm cultures of unamended sediments gradually release the equivalent of 0.03–0.30 μg/g As to the dissolved phase. The addition of glucose as a potential electron donor results in a marked stimulation in the mobilization of As (0.71–3.81 μg/g) in the amended incubations for all sediments. The quantity of As released accounts for 60–70% of As bound to Fe/Mn oxides in the original sediments. The microbially mediated mobilization of As with the organic nutrient as an electron donor is strongly associated with the As bound to Fe/Mn oxides, as well as the exchangeable As. During the incubations amended with glucose, 2–4% of the sediment Fe is released. The results suggest that the introduction of labile dissolved organic C into the yellowish sediment aquifers with As-free groundwater would reduce a significant proportion of the Fe(III) oxyhydroxides mediated by anaerobic bacteria respiration and increase groundwater As concentrations. 相似文献
20.
I. Radhakrishna 《Environmental Geology》2001,40(3):369-380
Saline/fresh water interface structure is one of the most important and basic hydrogeological parameter that needs to be
estimated for studies related to coastal zone management, well-field design and understanding saline water intrusion mechanism/processes.
The success and stability of a groundwater structure in a coastal region depend upon an accurate estimate of interface structure
between saline and fresh water zones, aquifer-aquiclude boundaries and their lateral continuities and the interstitial water
qualities of aquifers. Self-potential and resistivity logs provide a reasonably good basis for such estimates and for sustainable
development of fresh groundwater resources. The interface depth structure for the Mahanadi delta region, as obtained and interpreted
through self-potential and resistivity logs, provides a fairly clear picture of the regional extensions and boundaries of
aquifers, aquicludes and interstitial water quality patterns. Aquifers in the northern sector of the basin and within the
framework of Birupa and Mahanadi are characterized by an interface depth range that varies between 40 and 280 m below ground
level (bgl) with brackish water on the top underlain by freshwater aquifers. The aquifers in the southern sector within the
framework of Khatjori/Devi and Koyakhai/Daya/Kushbhadra/Bhargavi are characterized by an interface depth range that varies
from 10 to 120 m with freshwater aquifers near the surface underlain by saline, brackish water aquifers. The inversion of
these major fluid systems appears to have taken place over a narrow zone between Mahanadi and Khatjori tributaries, possibly
over a wide subsurface ridge with separate basin characteristics.
Received: 29 November 1999 · Accepted: 2 May 2000 相似文献