Using 87Sr/86Sr, δ18O and δ2H isotopes along with major chemical composition to assess groundwater salinization in lower Shire valley,Malawi

Groundwater resources in some parts of the lower section of Shire River valley, Malawi, are not useable for rural domestic water supply due to high salinity. In this study, a combined assessment of isotopic (⁸⁷Sr/⁸⁶Sr, δ¹⁸O and δ²H) and major ion composition was conducted in order to identify the hydro-geochemical evolution of the groundwater and thereby the causes of salinity. Three major end-members (representing fresh- and saline groundwater, and evaporated recharge) were identified based on major ion and isotopic composition. The saline groundwater is inferred to result from dissolution of evaporitic salts (halite) and the fresh groundwater shows influence of silicate weathering. Conservative mixing models show that brackish groundwater samples result from a three component mixture comprising the identified end-members. Hence their salinity is interpreted to result from mixing of fresh groundwater with evaporated recharge and saline groundwater. On the other hand, the groundwater with low TDS, found at some distance from areas of high salinity, is influenced by mixing of evaporated recharge and fresh groundwater only. Close to the Shire marshes, where there is shallow groundwater, composition of stable isotopes of water indicates that evaporation may also be an important factor.     

Hydrothermal contamination of public supply wells in Napa and Sonoma Valleys,California

Groundwater chemistry and isotope data from 44 public supply wells in the Napa and Sonoma Valleys, California were determined to investigate mixing of relatively shallow groundwater with deeper hydrothermal fluids. Multivariate analyses including Cluster Analyses, Multidimensional Scaling (MDS), Principal Components Analyses (PCA), Analysis of Similarities (ANOSIM), and Similarity Percentage Analyses (SIMPER) were used to elucidate constituent distribution patterns, determine which constituents are significantly associated with these hydrothermal systems, and investigate hydrothermal contamination of local groundwater used for drinking water. Multivariate statistical analyses were essential to this study because traditional methods, such as mixing tests involving single species (e.g. Cl or SiO₂) were incapable of quantifying component proportions due to mixing of multiple water types. Based on these analyses, water samples collected from the wells were broadly classified as fresh groundwater, saline waters, hydrothermal fluids, or mixed hydrothermal fluids/meteoric water wells. The Multivariate Mixing and Mass-balance (M3) model was applied in order to determine the proportion of hydrothermal fluids, saline water, and fresh groundwater in each sample. Major ions, isotopes, and physical parameters of the waters were used to characterize the hydrothermal fluids as Na–Cl type, with significant enrichment in the trace elements As, B, F and Li. Five of the wells from this study were classified as hydrothermal, 28 as fresh groundwater, two as saline water, and nine as mixed hydrothermal fluids/meteoric water wells. The M3 mixing-model results indicated that the nine mixed wells contained between 14% and 30% hydrothermal fluids. Further, the chemical analyses show that several of these mixed-water wells have concentrations of As, F and B that exceed drinking-water standards or notification levels due to contamination by hydrothermal fluids.     

Cation exchange in a temporally fluctuating thin freshwater lens on top of saline groundwater

In coastal-zone fields with a high groundwater level and sufficient rainfall, freshwater lenses are formed on top of saline or brackish groundwater. The fresh and the saline water meet at shallow depth, where a transition zone is found. This study investigates the mixing zone that is characterized by this salinity change, as well as by cation exchange processes, and which is forced by seepage and by rainfall which varies as a function of time. The processes are first investigated for a one-dimensional (1D) stream tube perpendicular to the interface concerning salt and major cation composition changes. The complex sequence of changes is explained with basic cation exchange theory. It is also possible to show that the sequence of changes is maintained when a two-dimensional field is considered where the upward saline seepage flows to drains. This illustrates that for cation exchange, the horizontal component (dominant for flow of water) has a small impact on the chemical changes in the vertical direction. The flow’s horizontal orientation, parallel to the interface, leads to changes in concentration that are insignificant compared with those that are found perpendicular to the interface, and are accounted for in the 1D flow tube. Near the drains, differences with the 1D considerations are visible, especially in the longer term, exceeding 100 years. The simulations are compared with field data from the Netherlands which reveal similar patterns.     

Delineation of groundwater salinization in a coastal aquifer, Bousheher, South of Iran

The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm^?1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br^?/Cl^? ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.     

Hydrogeochemistry of the Saloum (Senegal) superficial coastal aquifer

Seawater has entered and concentrated in the Saloum hydrologic system up to 100 km upstream, contaminating both the surface water and the superficial 'Continental terminal' (CT) groundwater resources, and large proportions of cultivated lands. In the areas affected by saltwater contamination, chloride concentrations as high as 3,195 mg/l have been measured in the groundwater samples collected from wells located in the vicinity of the Saloum River, making the water inadequate for drinking water purposes. This paper presents the results of a study designed to characterise the current extent of the saline groundwater and the mechanism of saline surface water body/fresh groundwater mixing in relation to the groundwater flow trends. It also describes the groundwater chemical and isotopic composition and geochemical processes controlling the chemical patterns. Four major water types occur in the study area, namely Na-rich saline groundwater, Ca-Na-rich saline groundwater, Na-dominant fresh groundwater and Ca-dominant fresh groundwater. A hydrogeochemical zonation of the aquifer, based on the presence of different water families and on the groundwater flow, led to the identification of the main processes controlling the groundwater chemistry. Cation exchange reactions on the kaolinite clay mineral, calcite dissolution in the eastern zone where calcite minerals have been identified, reverse cation exchange reactions in the saline-contaminated band along the Saloum River and, to a lesser extent, a gypsum dissolution are the predominant processes. Results of i¹⁸O and iD analysis in 15 groundwater samples compared with the local meteoric line indicate that the groundwater has been affected by evaporation, and the groundwater is isotopically lighter as the depth of water table increases. In this study, i¹⁸O data were used in conjunction with chloride data to identify the source of high chloride. Results show a departure of the contaminated water samples from the seawater mixing line, which indicates that other processes rather than mixing between modern seawater and native groundwater alone increase the chloride concentrations.     

The inter-relationship between coastal sub-aquifers and the Mediterranean Sea, deduced from radioactive isotopes analysis

Radioactive isotopes were used to estimate the rate of seawater intrusion into the coastal aquifer of Israel, the connection between the different sub-aquifers, and the connection between the sub-aquifers and the sea. This was done by dating both fresh and saline groundwaters from the vicinity of the shoreline, which were analyzed for their ¹⁴C and tritium content together with their chemical and stable isotope composition. The results indicate that the distinct sub-aquifers differ in their water chemistry and age. The saline groundwater in the lower sub-aquifers is older than ca. 10,000 years, as evidenced by the absence of tritium and low ¹⁴C activity (<12 PMC). On the other hand, saline groundwaters in the upper sub-aquifers contain tritium and are thus younger than 50 years, indicating recent intrusion of seawater. The ages of the saline groundwaters become younger upward from the lower sub-aquifers to the upper ones, reflecting the sea-level rise since the last glacial period. The older ages also imply slow groundwater flow in the lower sub-aquifers. The fresh groundwaters in most cases in the lower sub-aquifers were found to be older than ca. 10,000 years and this implies that the flow to the sea is blocked or restricted.     

Salinization and dilution history of ground water discharging into the Sea of Galilee,the Dead Sea Transform,Israel

The mechanism governing salinization of ground water discharging into the Sea of Galilee in Israel has been the subject of debate for several decades. Because the lake provides 25% of the water consumed annually in Israel, correct identification of the salt sources is essential for the establishment of suitable water-management strategies for the lake and the ground water in the surrounding aquifers. Existing salinization models were evaluated in light of available and newly acquired data including general chemistry, and O, H, C and Cl isotopes. Based on the chemical and isotopic observations, the proposed salt source is an ancient, intensively evaporated brine (21- to 33-fold seawater) which percolated through the valley formations from a lake which had formed in the Rift Valley following seawater intrusion during the late Miocene. Low Na:Cl and high Br:Cl values support the extensive evaporation, whereas high Ca:Cl and low Mg:Cl values indicate the impact of dolomitization of the carbonate host rock on the residual solution. Based on radiocarbon and other isotope data, the dilution of the original brine occurred in two stages: the first took place ∼30 000 a ago by slightly evaporated fresh-to-brackish lake water to form the Sea of Galilee Brine. The second dilution phase is associated with the current hydrological regime as the Sea of Galilee Brine migrates upward along the Rift faults and mixes with the actively circulating fresh ground water to form the saline springs. The spatially variable chemical and isotopic features of the saline springs suggest not only differential dilution by fresh meteoric water, but also differential percolation timing of the original brine into the tectonically disconnected blocks, registering different evaporation stages in the original brine. Consequently, various operations to reduce the brine contribution to the lake may be differentially effective in the various areas.     

Natural salinity sources in the groundwaters of Jordan—Importance of sustainable aquifer management

In recent years, voices in Jordan became lauder to exploit the fresh to brackish deep groundwater overlain by fresh groundwater bodies. In this article the implications of such a policy on the existing fresh water bodies are worked out through studying the sources of salinity in the different aquifer systems and the potentials of salinity mobilization by artificial changes in the hydrodynamic regimes. It is concluded that extracting the groundwater of deep aquifers overlain by fresh water bodies, whether the deep groundwater is fresh to brackish, brackish or salty, is equivalent to extracting groundwater from the overlying fresh groundwater bodies because of the hydraulic connections of the deep and the shallow aquifers’ groundwaters. The consequences are even more complicated and severe because exploiting the deep groundwater containing brackish or salty water will lead to refilling by fresh groundwater leaking from the overlying aquifers. The leaking water becomes salinized as soon as it enters the pore spaces of the emptied deep aquifer matrix and by mixing with the deep aquifer brackish or saline groundwater. Therefore, the move to exploit the deep groundwater is misleading and damaging the aquifers and is unjust to future generation's rights in the natural wealth of Jordan or any other country with similar aquifers’ set-up. In addition, desalination produces brines with high salinity which cannot easily be discharged in the highlands of Jordan (with only very limited access to the open sea) because they will on the long term percolate down into fresh water aquifers.     

咸化湖盆混积岩成因机理研究

关于海相及淡水湖盆混积岩的研究已相对完善,而针对咸化湖盆混积岩理论的形成及实践应用却鲜有报道,本文旨在系统地阐述咸化湖盆混积岩的成因机理、沉积模式、分布规律,对比其与一般混积岩沉积特征的异同点,并探讨其与油气富集特征的相关性。本文采用矿物学、微观岩石学分析方法进行混积岩矿物组成、沉积特征、储集空间类型研究,采取地质统计分析方法明确混积岩分布规律,并运用物性分析方法对比不同类型混积岩的储集性能。结合柴达木盆地西北区新近系混积岩研究实例,本文创新性地提出了欠补偿咸化湖盆的混积岩成因类型：机械成因的相混合混积岩和生物成因的藻混合混积岩。相混合又可划分为两种亚类：互层型混合、组构型混合;藻混合亦可划分为两种亚类：藻粘结混合、滑塌再混合。建立了咸化湖盆混积岩的沉积模式：混积岩主要发育于三角洲、水下扇、滩坝等碎屑岩沉积体系与湖相碳酸盐岩沉积体系的过渡相带以及藻灰岩发育区。明确了混积岩的分布规律,可归纳为“盆缘互层型、盆内组构型、藻混合局限分布”。混积岩沉积特征对比分析结果表明,任何环境下混积岩形成的先决条件均为碳酸盐岩的生长和聚集,而不同于淡水湖盆及海相混积岩沉积厚度大,生物含量高等特点,咸化湖盆混积岩单层厚度极薄,并发育特殊的藻混积岩类。综合研究认为,藻混合混积岩与油气储层的相关性要大于相混合混积岩。以上成果可为咸化湖盆混积岩,乃至陆相湖泊混合沉积物的成因类型及油气地质意义研究提供借鉴与参考。     

Geochemistry and origin of saline groundwaters in the Fennoscandian Shield

Chemical and isotopic analyses of water from drill holes and mines throughout the Fennoscandian Shield show that distinct layers of groundwater are present. An upper layer of fresh groundwater is underlain by several sharply differentiated saline layers, which may differ in salinity, relative abundance of solutes, and O, H, Sr and S isotope signature. Saline groundwater can be classified into four major groups based on geochemistry and presumed origin. Brackish and saline waters from 50–200 m depth in coastal areas around the Baltic Sea exhibit distinct marine chemical and isotopic fingerprints, modified by reactions with host rocks. These waters represent relict Holocene seawater. Inland, three types of saline groundwater are observed: an uppermost layer of brackish and saline water from 300–900 m depth; saline water and brines from 1000–2000 m depth; and superdeep brines which have been observed to a depth of at least 11 km in the drill hole on the Kola Peninsula, U.S.S.R. Electrical and seismic studies in shield areas suggest that such brines are commonly present at even greater depths. The salinity of all inland groundwaters is attributed predominantly to water-rock interaction. The main solutes are Cl, Ca, Na and Mg in varying proportions, depending on the host rock lithology. The abundance of dissolved gases increases with depth but varies from site to site. The main gas components are N₂, CH₄ (up to 87 vol.%) and locally H₂. The δ¹³C value for methane is highly variable (−25 to −46%), and it is suggested that hydrothermal or metamorphic gases trapped within the surrounding rocks are the most obvious source of CH₄. The uppermost saline water has meteoric oxygen-hydrogen isotopic compositions, whereas values from deeper water plot above the meteoric water line, indicating considerably longer mean residence time and effective low temperature equilibration with host rocks. Geochemical and isotopic results from some localities demonstrate that the upper saline water cannot have been formed through simple mixing between fresh water and deep brines but rather is of independent origin. The source of water itself has not been satisfactorily verified although superdeep brines at least may contain a significant proportion of relict Precambrian hydrothermal or metamorphic fluids.     

Submarine groundwater discharge in a subsiding coastal lowland: A Ra and Rn investigation in the Southern Venice lagoon

Several recent studies have suggested that submarine groundwater discharge (SGD) occurs in the Venice lagoon with discharge rates on the same order or larger than the surface runoff, as demonstrated previously in several other coastal zones around the world. Here, the first set of ²²²Rn data, along with new ²²⁶Ra data are reported, in order to investigate the occurrence and magnitude of SGD specifically in the southern basin of the lagoon. The independent connection with the Adriatic Sea (at the Chioggia inlet), in addition to the relative isolation of the water body from the main lagoon, make this area an interesting case study. There is probably only minimal fresh groundwater flux to the lagoon because the surrounding aquifer is subsiding and mainly has a lower hydraulic head than seawater.The data show that the Ra and Rn activities are in slight excess in the lagoon compared to the open sea, with values on the same order as those observed in the northern and central basins. Taking into account the water exchange rate between the lagoon and adjacent seawater provided by previous hydrodynamic numerical modelling, it is shown that this excess cannot be supported at steady state by only riverine input and by diffusive release from the sediment interstitial water. High activities observed in groundwater samples collected from 16 piezometers tapping into the shallow aquifer over the coastal lowland substantiate that the excess radioactivity in the lagoon may indeed be due to the advection of groundwater directly into the lagoon bottom water through the sediment interface. However, the data show that the groundwater composition is extremely heterogeneous, with high Ra activities concentrated within a narrow coastal strip where the contact between fresh and saline water takes place, while Rn strongly decreases when approaching the lagoon shore across the 20 km coastal plain. Assuming that the average groundwater activities measured in the coastal strip are representative of the SGD composition, a SGD flux of 7.7 ± 3.5 × 10⁵ and 2.5 ± 2 × 10⁶ m³/d is calculated using a ²²⁶Ra and ²²²Rn budget, respectively, (i.e. about 1-3 times the surface runoff), substantially lower than in previous studies. The influence of all assumptions on SGD estimates (groundwater heterogeneity, diffusive sediment flux, one-box versus multi-boxes model calculations) is discussed, and a sensitivity analysis of the influence of imperfect exchange and mixing at the lagoon outlets that affects the lagoon composition is provided. Finally, the results confirm that the SGD flux, calculated with these assumptions, is largely (∼80%) composed of saline lagoon water circulating through the sediment under the lagoon margin, and that the fresh water discharge associated with SGD is at most a minor term in the lagoon hydrologic balance.     

Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia

Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water, and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line. This explained the most visible processes taking place during the displacement.     

87Sr/86Sr in waters from the Lincolnshire Limestone aquifer,England, and the potential of natural strontium isotopes as a tracer for a secondary recovery seawater injection process in oilfields

The Sr isotope composition of formation waters is a sensitive indicator of diagenetic processes in the host sediments, mixing processes between different bodies of water, and the connectivity of hydrological systems. The⁸⁷Sr/⁸⁶Sr ratio of present seawater is constant worldwife, while formation waters in hydrocarbon reservoirs have various values, depending on the aforementioned effects, in most cases different from modern seawater. This forms the basis of anatural tracer technique for seawater injection projects, involving characterization of the⁸⁷Sr/⁸⁶Sr ratios and Sr contents of formation waters in the reservoir before injection commences, followed by monitoring of these parameters in the produced water as injection proceeds. This method is best suited to reservoirs in which the formation waters have low Sr concentrations and⁸⁷Sr/⁸⁶Sr ratios much higher or lower than seawater. Available data for reservoir formation waters suggest that breakthrough recognition could be expected at <10% seawater in many sandstone reservoirs, while the method would be less sensitive in carbonate reservoir or situations where the formation waters had interacted with evaporites, as the associated waters tend to have high Sr contents. In heterogeneous but well-mapped reservoirs, it may be possible to obtain information about flow paths/mechanismsbefore breakthrough. Combination with other chemical and isotopic tracers creates a very powerful tool, the Sr method acting as a safeguard should the batch of water containing the conventional tracers be overtaken by subsequently injected seawater. The Sr method could also be used for injection projects that were begun without the addition of tracers. A natural analogue of a water injection process is found in the Jurassic Lincolnshire Limestone aquifer in England, where rapidly moving fresh meteoric water mixes progressively with an older saline formation water. The⁸⁷Sr/⁸⁶Sr data enable quantitative modelling of this mixing process. The infiltrating fresh water becomes progressively modified by dissolution of detrital carbonate and calcite cement in the limestone, with depth becoming increasingly dominated by Sr derived from the more soluble detrital components. The saline formation water contains water molecules of meteoric origin and an⁸⁷Sr/⁸⁶Sr ratio much higher than Jurassic seawater or marine carbonate; the solute content has been influence by interaction of the water with non-carbonate phases.     

Saline fresh water interface structure in Mahanadi delta region, Orissa, India

 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     

On the spreading mechanism of shallow groundwater in the Hinterland of the Dutch Dune hill area

The low lying Western part of the Netherlands is protected from the sea by a 5 km wide stretch of dunes rising to some 50 m of height. The fresh water pocket in the dunes overlies saline groundwater and a brackish transition zone. There was during a century an extraction of fresh groundwater for drinking water, supported by artificial infiltration. This has been stopped some 30 years ago. The consequent wetting of the valuable farm area (flower cultures) behind the dunes is stronger and more extensive than could be expected from mere replenishment of the fresh water zones in the dunes. It is shown in this paper that the lateral shear flows in the brackish and saline groundwater area have displaced (and are displacing) the interfaces vertically downward. The effect of more fresh and less saline groundwater in an arbitrary groundwater column is an (extra) rise of the groundwater head of the upper fresh water part. The described slow process will continue for decades until a new equilibrium has been established. In the mean time the inner dune farm area will have to cope with a surprisingly strong and extensive water level rise.     

Hydrogeochemical conditions and evolution at the Äspö HRL,Sweden

The overall hydrogeochemical conditions at and in the near vicinity of the underground experimental Äspö Hard Rock Laboratory (HRL) in SE Sweden have been investigated. Groundwater data from more than 400 samples have been compiled and evaluated. The groundwater samples represent depths down to 1700 m below sea level and sampling has been performed prior to and during the HRL tunnel excavation. Episodic events have to a great extent influenced the hydrochemical evolution since the last glaciation which ended some 13 ka ago. At that time glacial melt water was flushed under hydraulic pressure down into the fracture system to a depth of at least several hundred metres. The next episodic event took place when the Baltic freshwater lake transformed into the brackish Litorina Sea some 7 ka ago. At this time Äspö was covered by the sea and these denser, more saline waters partly replaced the glacial water down to a depth where the density equilibrated with the replacement sea water. At some time around 3–4 ka ago, Äspö started to rise above sea level and meteoric water began to infiltrate the rock.The overall trend of increasing salinity with depth may easily be misinterpreted as a fairly simple groundwater system, evolving from a two component evolution path between non-saline and saline groundwaters. However, when combining the results from environmental isotopes and the chemical parameters using a new modelling tool named M3 (Multivariate Mixing and Mass balance calculations), a higher resolution was obtained and a more complex groundwater pattern, which reflects the present and paleo-hydrogeological events, can be recognised.The measured groundwater composition was modelled to be a mixture of meteoric, past and present Baltic seawater, glacial (or cold climate recharge) and brine type of waters. The modelling result shows that the processes considered to have a dominating impact on the present Äspö groundwater chemistry are mixing, both in disturbed and undisturbed systems, calcite dissolution and precipitation, redox reactions and biological processes. The undisturbed groundwater conditions prior to the HRL tunnel construction at Äspö consisted of:

• 1.A dominating proportion of meteoric fresh water in the upper 250 m of the aquifer.
• 2.A brackish–saline water consisting of mixing proportions of present and ancient Baltic Sea water and glacial melt water present to a depth of 250–600 m.
• 3.Saline water still containing proportions of glacial water which could represent even older glaciations, and brines, a large portion of which have been stagnant for perhaps millions of years, below a depth of 600 m.

During the HRL tunnel construction there were changes in the composition of the water flowing into the tunnel at different locations. Although the variation in salinity was relatively small, the variations in the mixing proportions of the different water types were substantial.     

An integrated approach to investigate saline water intrusion and to identify the salinity sources in the Central Godavari delta, Andhra Pradesh, India

The Central Godavari delta is located along the Bay of Bengal Coast, Andhra Pradesh, India, and is drained by Pikaleru, Kunavaram and Vasalatippa drains. There is no groundwater pumping for agriculture as wells as for domestic purpose due to the brackish nature of the groundwater at shallow depths. The groundwater table depths vary from 0.8 to 3.4 m and in the Ravva Onshore wells, 4.5 to 13.3 m. Electrical Resistivity Tomography (ERT) surveys were carried out at several locations in the delta to delineate the aquifer geometry and to identify saline water aquifer zones. Groundwater samples collected and analyzed for major ions for assessing the saline water intrusion and to identify the salinity origin in the delta region. The results derived from ERT indicated low resistivity values in the area, which can be attributed to the existence of thick marine clays from ground surface to 12–15 m below ground level near the coast and high resistivity values are due to the presence of coarse sand with freshwater away from the coast. The resistivity values similar to saline water <0.01 Ω m is attributed to the mixing of the saline water along surface water drains. In the Ravva Onshore Terminal low resistivity values indicated up coning of saline water and mixing of saline water from Pikaleru drain. The SO ₄ ^?2 /Cl^?and Na⁺²/Cl^?ratios did not indicate saline water intrusion and the salinity is due to marine palaeosalinity, dilution of marine clays and dissolution of evaporites.     

Saline groundwaters in the hercynian granites (Chardon Mine,France): geochemical evidence for the salinity origin

In this study, the chemical evolution of high Cl⁻ Chardon mine groundwaters is modelled as a mixing between an oxidising recharge and an old marine component on which the water–rock interaction is superimposed. Chemical and isotopic similarities with saline Carnmenellis mine groundwaters are emphasised and a general comparison with other brines is discussed.The cation content of deep granitic groundwaters is indicative of the water–rock interaction. In the case of Chardon and Carnmenellis groundwaters, the high Na/Cl ratio can still be related to the contribution of a brine of sedimentary origin to the water salinity. The differences in the hydrochemistry related to their geological context only appears at the trace metals level. On the contrary, brines in plutonic rocks which exhibit a low Na/Cl ratio represent groundwaters having a residence time in the host rock, long enough to equilibrate with secondary aluminosilicates. In that case, the brine origin is difficult to assess if only based on the water cation content.     

海底金矿矿坑涌水水源判识及演化研究

为查明新立海底金矿浅部裂隙涌水在开采条件下的演化规律,从水文地球化学的角度出发,提出采用主成分分析法和最大似然概率法对裂隙涌水水源及其混合比进行判识和计算,并采用数值模拟法间接验证计算结果的可靠性。研究表明:该方法能够有效识别矿山涌水水端元的组合模型及其变化,计算出可能性最大的端元混合比;新立金矿浅部裂隙涌水端元模型经历了由Ⅰ类基岩水+海底地下水到Ⅰ类基岩水+海底地下水+现代海水的演化过程;海底地下水和现代海水易从采空区两侧肩部进入矿坑,且涌水中海水含量呈现先增加后减小的变化规律。     

以色列依靠科技创新走出缺水困境的经验

以色列地处中东,降雨稀少且分布不均,天然淡水资源短缺。为解决这一困境,以色列自1948年建国后就一直致力于发展水资源高效利用技术,在水资源生产、运输、回收等领域研发出诸多领先全球的新技术。经过多年努力,该国从一个缺水的国家成为高效用水的农业大国,甚至被誉为“欧洲国家的菜篮子”。文章首先介绍了以色列的地理气候情况和水资源类型,然后介绍了水资源利用结构,最后列举了以色列在解决水资源危机时发展的6项创新技术。文章可为我国水资源高效利用与管理提供借鉴,同时也可为今后我国与以色列开展水资源方面的相关合作及学术研究提供基础资料。