共查询到20条相似文献，搜索用时 691 毫秒
1.
Zhou Xun Chen Mingyou Wan Li Department of Water Resources Environmental Engineering China University of Geosciences Beijing China Wang Juping Ning Xuesheng Beihai Institute of Hydrogeology Engineering Geology Mineral Resour 《中国地质大学学报(英文版)》2000,11(3)
INTRODUCTIONThe city of Beihai,located on the south coast ofGuangxi,China,relies heavily on groundwater for its potablewater supply and agricultural irrigation.With rapid increasein population (for instance,from 134 0 0 0 in 1987to 47930 0in1995 ) and in developm ent program s,the demand for freshwater has been growing. Approxim ately 170 0 0 0 m3/ d ofgroundwater has been pumped from the productive coastalaquifers in recent years.Contamination of the fresh water inthe coastal aquifers b… 相似文献
2.
Water extractions in coastal areas have to deal with salt water intrusion and lowering of hydraulic heads in valuable ecosystems.
Therefore, sustainable management of fresh water resources in these areas is crucial. This is illustrated here with two water
extractions in the western Belgian coastal plain which extract groundwater from a phreatic dune aquifer. One water extraction
faced problems with salt water intrusion, while lowering of hydraulic heads was an issue for both. To remedy the salt water
intrusion, it was found that decreasing the extraction rate was the only solution. To offset this and to increase hydraulic
heads around both extractions, it was decided to artificially recharge the aquifer of the second extraction with tertiary
treated wastewater. By taking these interventions, the combined production capacity of the water extractions was increased
with 56% whereas 27% less water was extracted from the dune aquifer itself. Extraction history and the effects of interventions
are illustrated for both water extractions with water quality data and fresh water head observations. A more detailed insight
in groundwater flow and fresh–salt water distribution in the aquifer is provided by simulating the evolution of the water
extractions with a 3D density dependent groundwater flow model. 相似文献
3.
4.
The study area, the Fasa Plain, is situated in the semiarid region of Fars Province in the south of Iran. The Salloo diapir is a salt dome that crops out in the northwest of the study area. Isotopic and hydrochemical analyses were used to examine the water and how the origin of salinity and the diapir affect the quality of the groundwater quality in the study area. Groundwater was sampled from 31 representative pumping wells in alluvial aquifer and five springs in order to measure their stable isotope compositions, bromide ion concentration, and physical and chemical parameters. The alluvial aquifer was organized into two main groups based on the chemistry, with Group 1 consisting of low-salinity well samples (544–1744 µS/cm) with water type Ca–Mg–HCO3–SO4 which were taken in the center and north of the area, and Group 2 consisting of high-salinity samples (2550–4620 µS/cm) with water type Ca–Mg–Cl–SO4 which were taken from the wells in the south and southwest of the area. A saline spring near the salt dome with an EC of 10,280 µS/cm has water type Na–Cl, while the compositions of the water in the other karstic springs is comparable to the fresh groundwater samples. All groundwater samples are undersaturated with respect to gypsum, anhydrite, and halite and are supersaturated with respect to calcite and dolomite. Stable isotopes (δ18O and δ2H) differentiated four water types: saline springs, freshwater spring, fresh groundwater, and saline groundwater. The results indicate that meteoric water is the main origin of these water resources. Halite dissolution from the salt dome was identified as the origin of salinity. The Na/Cl and Cl/Br ratios confirmed the results. Groundwater compositions in the southwestern part of the area are affected by the intrusion of saltwater from the salt dome. The average saltwater fraction in the some water wells is about 0.2%. In the south and southwestern part of the area, the saltwater fraction is positive in mixed freshwater/saltwater (Group 2). Different processes interact together to change the hydrochemical properties of Fasa’s alluvial aquifer. The main processes that occur in the aquifer are mixing, gypsum dissolution, and calcite precipitation. 相似文献
5.
Hydrochemistry of groundwater and its assessment for irrigation purpose in coastal Jeffara Aquifer, southeastern Tunisia 总被引：1，自引：0，他引：1
Groundwater is of a paramount importance in arid areas, as it represents the main water resource to satisfy the different needs of the various sectors. Nevertheless, coastal aquifers are generally subjected to seawater intrusion and groundwater quality degradation. In this study, the groundwater quality of the coastal Jeffara aquifer (southeastern Tunisia) is evaluated to check its suitability for irrigation purposes. A total of 74 groundwater samples were collected and analyzed for various physical and chemical parameters, such as, electrical conductivity, pH, dissolved solids (TDS), Na, K, Ca, Mg, Cl, HCO3, and SO4. Sodium adsorption ratio, magnesium adsorption ratio, Sodium percentage, and permeability index were calculated based on the analytical results. The analytical results obtained show a strong mineralization of the water in the studied aquifer. TDS concentrations range from 3.40 to 18.84 g?L?1. Groundwater salinity was shown to be mainly controlled by sodium and chloride. The dominant hydrochemical facieses are Na–Cl–Ca–SO4, mainly as a result of mineral dissolution (halite and gypsum), infiltration of saline surface water, and seawater intrusion. Assessment of the groundwater quality of the different samples by various methods indicated that only 7% of the water, in the northwest of the study area, is considered suitable for irrigation purposes while 93% are characterized by fair to poor quality, and are therefore just suitable or unsuitable for irrigation purposes. 相似文献
6.
Agua Amarga coastal aquifer in southern Spain has been the subject of chemical and physical measurements since May 2008 in order to monitor the potential effects of water withdrawal for the Alicante desalination plants on the salt marsh linked to the aquifer. Electrical conductivity contour maps and depth profiles, piezometric-head contour maps, hydrochemical analyses, isotopic characterizations and temperature depth profiles show not only the saltwater intrusion caused by water abstraction, but also the presence of a pronounced convective density-driven flow below the salt marsh; this flow was a consequence of saltwork activity in the early 1900s which generated saline groundwater contamination. The influence of a seawater recharge programme, carried out over the salt marsh in 2009–2010, on the diminishing groundwater salinity and the recovery of groundwater levels is also studied. Based on collected field data, the project provides a deeper understanding of how these successive anthropogenic interventions have modified flow and mixing processes in Agua Amarga aquifer. 相似文献
7.
Greece is dependent on groundwater resources for its water supply. The main aquifers are within carbonate rocks (karstic aquifers)
and coarse grained Neogene and Quaternary deposits (porous aquifers). The use of groundwater resources has become particularly
intensive in coastal areas during the last decades with the intense urbanization, tourist development and irrigated land expansion.
Sources of groundwater pollution are the seawater intrusion due to over-exploitation of coastal aquifers, the fertilizers
from agricultural activities and the disposal of untreated wastewater in torrents or in old pumping wells. In the last decades
the total abstractions from coastal aquifers exceed the natural recharge; so the aquifer systems are not used safely. Over-exploitation
causes a negative water balance, triggering seawater intrusion. Seawater intrusion phenomena are recorded in coastal aquifer
systems. Nitrate pollution is the second major source of groundwater degradation in many areas in Greece. The high levels
of nitrate are probably the result of over-fertilization and the lack of sewage systems in some urban areas. 相似文献
8.
Xun Zhou 《Environmental Earth Sciences》2014,71(3):1311-1317
In a coastal zone an understanding of the distance of the fresh water–salt water interface and its extension inland is important for prevention of sea water intrusion. In this article estimating methods are described for calculating the distance of a fresh water–salt water interface in a coastal confined aquifer based on the submarine fresh groundwater discharge. This groundwater discharge is controlled not only by the aquifer properties and hydraulic head difference, but also by the position of the fresh water–salt water interface in the coastal zone. A homogeneous and isotropic coastal confined aquifer is considered and fresh groundwater flow in the confined aquifer is thought to be at a steady state. Two observation wells at different distances in a profile perpendicular to the coastline are required in calculation of the distance of the interface toe in the coastal zone. Four coastal confined aquifers with horizontal and sloping confining beds and with varying thickness are also considered. Reasonable results are obtained when examples are used to illustrate the application of the methods. The methods require hydraulic head data at the two wells and thickness of the confined aquifers, but the hydraulic conductivity and fresh groundwater flow rate of the confined aquifers are not needed. 相似文献
9.
Evolution of the groundwater environment under a long-term exploitation in the coastal area near Zhanjiang, China 总被引：3，自引：0，他引：3
Aquifers consisting of unconsolidated sediments in the coastal area near Zhanjiang in southern China are grouped into the
shallow, middle-deep and deep aquifer systems. Groundwater exploitation began in the 1950s in this district and has increased
from year to year since 1980. Measurements of groundwater levels and monitoring data of groundwater chemistry at some 60 wells
since 1981 are examined to analyze the evolution of hydrodynamics and hydrochemistry in the coastal aquifers. The results
indicate that groundwater levels in the middle-deep and deep aquifer systems have fallen continuously and the extents of the
depression cones in water levels have increased in the past two decades, even though the water levels recovered to some degree
during the period of 1997–2001. In 2004, the lowest water levels in the middle-deep and deep aquifer systems were 23.58 and
21.84 m below sea level, respectively. The groundwater has TDS ranging from 40 to 550 mg/L, and is of low pH, commonly varies
between 4 and 7. Concentrations of total iron and manganese exceed the concentration limits of the drinking water standards.
The hardness is in the range of 10–250 mg/L. Chloride contents of the groundwater range from 10 to 60 mg/L. The chloride and
TDS do not show systematically increasing trends. Although the water levels in the exploitation center near the coast are
significantly lower than the sea level and the depression cones of water levels in the middle-deep and deep aquifer systems
have expanded to the sea, sea water intrusion has not been observed until recently. This phenomenon is quite unique in the
coastal area near Zhanjiang. 相似文献
10.
Adel Kharroubi Faten Tlahigue Belga?em Agoubi Chafai Azri Salem Bouri 《Environmental Earth Sciences》2012,67(7):2089-2100
Coastal aquifers are considered as major sources for freshwater supply worldwide, especially in arid zones. The weak rainfall as well as the intensive extraction of groundwater from coastal aquifers reduce freshwater budget and create local water aquifer depression, causing both seawater intrusion and a threat to groundwater. This phenomenon was observed in the Jerba Island which is located in southeast Tunisia. Jerba??s unconfined aquifer shows high values of groundwater salinity reaching, locally, 17?g/l and a strong contrast between some zones of the aquifer. High pumping rates and weak recharge disturb the natural equilibrium between fresh and saline water causing water salinization in most areas of the island. This study aims at establishing the salinity map of the aquifer and identifying the origin of groundwater salinization. The salinity map shows that zones characterized by low groundwater salinity are located in the center of the study area. High groundwater salinities are observed near the coast and in some parts having low topographic and piezometric levels. Groundwater geochemical characterization, and Br/Cl and Na/Cl ratios suggest that the origin of abnormal salinity is seawater intrusion. Considering groundwater salinity values and Br concentrations, a seawater intrusion map is established. It shows that many areas of the unconfined aquifer are contaminated by mixed groundwater and seawater. The statistical analysis demonstrates that high mineralization of the groundwater is due to gypsum and carbonate dissolution coupled with the mixed groundwater and seawater in many areas. 相似文献
11.
The present study concerns the application of a numerical approach to describe the influence of anthropogenic modifications in surface flows (operation of a projected reservoir) on the freshwater-seawater relationships in a downstream coastal aquifer which has seasonal seawater intrusion problems (River Verde alluvial aquifer, Almuñécar, southern Spain). A steady-state finite element solution to the partial differential equation governing the regional motion of a phreatic surface and the resulting sharp interface between fresh water and salt water was used to predict the regional behavior of the River Verde aquifer under actual surface flow conditions. The present model approximates, with simple triangular elements, the regional behavior of a coastal aquifer under appropriate sinks, sources, Neumann and open boundary conditions. A steady-state solution to this numerical approach has been shown to precisely calculate freshwater heads, saltwater thicknesses, and freshwater discharges along steeply sloping coasts. Hence, the adequate treatment and interpretation of the hydrogeological data which are available for the River Verde aquifer have been of main concern in satisfactorily applying the proposed numerical model. Present simulated conditions consider steady-state yearly averaged amounts of external supplies of fresh water in order to determine the influences of the projected Otívar reservoir on the further behavior of the River Verde coastal aquifer. When recharges occur at the coastline, essentially because of freshwater deficits due to groundwater overexploitation, a hypothesis of mixing for the freshwater-saltwater transition zone is made in order to still allow the model to continue calculating groundwater heads under the sea level, and, as a consequence, the resulting seawater intrusion and recharges of saltwater from the sea. Simulations show that a considerable advance in seawater intrusion would be expected in the coastal aquifer if current rates of groundwater pumping continue and a significant part of the runoff from the River Verde is channeled from the Otívar reservoir for irrigation purposes. 相似文献
12.
Groundwater is a crucial resource on the Manukan Island as it is the only source of freshwater available on the island. The aquifer has deteriorated to a high degree, during the last decade. Nine domestic wells were sam-pled from March 2006 to January 2007 to probe the hydrochemical components that influence the water quality. Geochemical data on dissolved major constituents in groundwater samples from the Manukan Island revealed the main processes responsible for their geochemical evolution. The results using statistical analyses, graphical method and numerical model output (PHREEQC) showed that the groundwater was chemically highly enriched in Na and Cl, indicative of seawater intrusion into the aquifer as also supported from the Na-Cl signature on the Piper diagram. From the PHREEQC simulation model, calcite, dolomite and aragonite solubility showed positive values of the saturation indices (SI), indicating supersaturation which led to mineral precipitation condition of water by these min-erals. 相似文献
13.
Groundwater salinization of the Sfax superficial aquifer,Tunisia 总被引：5，自引：0，他引：5
Groundwater salinization has become a crucial environmental problem worldwide and is considered the most widespread form of groundwater contamination. The origin of salinity in the coastal aquifer of the Sfax Basin, Tunisia was investigated by means of chemical analyses of groundwater samples from 65 wells. The groundwater samples present a clear gradation from calcium sulphate salinization to that of sodium chloride. The saturation indices for calcite and gypsum, and binary diagrams of different ions, together with multivariate analysis, indicate the existence of various salinization processes such as: dissolution of gypsum and calcite dispersed through the reservoir rock; ion exchange; intensive agricultural practices that produce effluents that infiltrate to the saturated zone; and sea-water intrusion, enhanced by excessive withdrawal of groundwater. 相似文献
14.
A thirty-year artificial recharge experiment in a coastal aquifer in an arid zone: The Teboulba aquifer system (Tunisian Sahel) 总被引：1，自引：0，他引：1
With the increased demand for groundwater resulting from fast demographic growth, accelerated urbanization, economic and agricultural activity diversification, and the increase of per capita consumption, ground water resources, in particular in coastal regions, remain relatively low, compared to demand. The groundwater quality and piezometric variations result mainly from intensive exploitation, agricultural activities and the intrusion of seawater. This phenomenon is observed mostly in semi-arid areas, such as the oriental Sahel of Tunisia, where an apparent reduction in rainfall in recent years can be seen. Groundwater becomes overexploited especially as its natural recharge by rainwater does not succeed in maintaining the hydrologic balance. The imbalance between water demand and resources induces the degradation of the water quality. In such a case, the artificial recharge of water-table aquifers by water from dams is a credible alternative to improve the hydrodynamic and physicochemical conditions of the groundwater. Like most coastal aquifers, the Teboulba water-table aquifer is threatened by overexploitation for at least three decades. This threat appears by a considerable piezometric level drop and by water salinisation, due to seawater intrusion. Given this alarming situation, since 1971, artificial recharge through wells with surface water from a dam was tested in order to restore the water levels and to improve water quality. The piezometric and chemical surveys of the Teboulba aquifer permitted one to describe the temporal and spatial piezometric and geochemical conditions of the aquifer and to show the effect of the artificial recharge. Indeed, the artificial recharge undertaken since 1971 made the geochemical and piezometric conditions of the Teboulba aquifer improve. This example is a rare, well-documented case-study of the benefits of artificial recharge in a coastal aquifer, over the long term. 相似文献
15.
A shallow alluvial coastal aquifer in the Batinah area of Oman, with sea-water intrusion that extends several kilometres inland, has been studied experimentally, analytically and numerically. The water table is proved to have a trough caused by intensive pumping from a fresh groundwater zone and evaporation from the saline phreatic surface. Resistivity traverses perpendicular to the shoreline indicated no fresh groundwater recharge into the sea. Using an analytical Dupuit-Forchheimer model, developed for the plain part of the catchment, explicit expressions for the water table, sharp interface location and stored volume of fresh water are obtained. It is shown that by the pumping of salt water from the intruded part of the aquifer, this intrusion can be mitigated. Different catchment sizes, intensities of fresh groundwater pumping, evaporation rates, water densities, sea level, incident fresh water level in the mountains and hydraulic conductivity are considered. SUTRA code is applied to a hypothetical case of a leaky aquifer with line sinks modeling fresh water withdrawal and evaporation. The numerical code also shows that pumping of saline water can pull the dispersion zone back to the shoreline. 相似文献
16.
Hydrogeochemistry and cation-exchange processes in the coastal aquifer of Mar Del Plata,Argentina 总被引：2，自引：3，他引：2
The aquifer of Mar del Plata is unconfined and composed of silt and fine sand. The sand fraction is mainly quartz, potassium
feldspars, chalcedony, and gypsum. Volcanic-glass shards (40–60%) dominate the silt fraction, and the clays are of the smectite
and illite groups. Calcium carbonate, in caliche form, constitutes about 10–20% of the sediment.
Groundwater flow is from west to east, and discharge is in the Atlantic Ocean. Because of overexploitation, the flow direction
was reversed in a coastal belt about 3.5 km wide, and this has resulted in seawater intrusion. The groundwater is the CaHCO3 type in the recharge zone, and becomes NaHCO3 type towards the discharge area. Salinization by marine intrusion and seawater/fresh-water mixing produces an increase in
the major-ion concentrations of the groundwater. The calcium content of the groundwater is higher and the sodium content is
lower than those that would be expected if the mixing is considered as just the addition of seawater and fresh water in determined
proportions without reactive processes taking place.
Hydrogeochemical modeling was applied to the study of hydrogeochemical processes, mainly cation exchange, using the codes
NETPATH and PHREEQM. Calcite and gypsum equilibrium, together with cation exchange, are the main hydrogeochemical processes.
Cation-exchange capacity of the solid phase was determined by empirical calculations and experimental methods. The affinity
order for the groundwater in contact with the aquifer matrix is Ca>Mg>Na in the regional-flow system, but the order is reversed
in the salinization process. Reactive transport modeling using the code PHREEQM is useful for analyzing cation exchange in
a marine-intrusion process.
Electronic Publication 相似文献
17.
Md. Mizanur Rahman Sarker Marc Van Camp Mazeda Islam Nasir Ahmed Kristine Walraevens 《Environmental Earth Sciences》2018,77(2):39
In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200–300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater. 相似文献
18.
Bjørn Kløve Hanne Margrethe Lund Kvitsand Tarja Pitkänen Maria J. Gunnarsdottir Sylvi Gaut Sigurdur M. Gardarsson Pekka M. Rossi Ilkka Miettinen 《Hydrogeology Journal》2017,25(4):1033-1044
The characteristics of groundwater systems and groundwater contamination in Finland, Norway and Iceland are presented, as they relate to outbreaks of disease. Disparities among the Nordic countries in the approach to providing safe drinking water from groundwater are discussed, and recommendations are given for the future. Groundwater recharge is typically high in autumn or winter months or after snowmelt in the coldest regions. Most inland aquifers are unconfined and therefore vulnerable to pollution, but they are often without much anthropogenic influence and the water quality is good. In coastal zones, previously emplaced marine sediments may confine and protect aquifers to some extent. However, the water quality in these aquifers is highly variable, as the coastal regions are also most influenced by agriculture, sea-water intrusion and urban settlements resulting in challenging conditions for water abstraction and supply. Groundwater is typically extracted from Quaternary deposits for small and medium municipalities, from bedrock for single households, and from surface water for the largest cities, except for Iceland, which relies almost entirely on groundwater for public supply. Managed aquifer recharge, with or without prior water treatment, is widely used in Finland to extend present groundwater resources. Especially at small utilities, groundwater is often supplied without treatment. Despite generally good water quality, microbial contamination has occurred, principally by norovirus and Campylobacter, with larger outbreaks resulting from sewage contamination, cross-connections into drinking water supplies, heavy rainfall events, and ingress of polluted surface water to groundwater. 相似文献
19.
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. 相似文献
20.
环境同位素特征对滨海岩溶地区海水入侵过程的指示意义 总被引：1，自引：0，他引：1
大连大魏家水源地位于中国北方典型滨海岩溶地区。近30年来,地下淡水的不合理开采造成的地下水位降落漏斗引发了严重的海水入侵。以大魏家水源地为研究对象,通过大量的水文地质调查和水化学及同位素采样测试分析,探讨海水入侵形成的水动力条件,通过分析滨海岩溶含水层中地下水主要水化学和多种同位素(δ2H-δ18O,δ34S,δ13C)组成特征,识别了海水入侵过程中发生的主要水文地球化学作用,并对其进行了定量模拟,从而阐明了岩溶含水层中的海水入侵机理。研究结果表明:大连大魏家海水入侵主要通道为大魏家地区存在的导水断裂、岩溶裂隙以及第四系松散地层。对δ2H-δ18O同位素的组成分析表明,研究区地下水主要来自大气降水补给,结合Cl-浓度分布,认为除海水入侵淡水含水层后增加了地下水中的盐分外,浅层地下水的蒸发也对地下水中盐分的累积起到了重要作用。根据不同水体中δ34SSO4,δ13CHCO3等同位素特征,结合水化学成分(如SO2-4,Cl-)分析认为,研究区微咸水和咸水并不是地下水淡水和海水简单混合而成。利用反向水文地球化学模拟揭示了控制滨海岩溶含水层中水化学演化的主要水文地球化学反应有方解石、蒙脱石和石膏的溶解作用,伊利石的沉淀作用以及Ca-Na离子交换作用,伴随着CO2的释放。 相似文献