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1.
Understanding of saline intrusion into coastal aquifer is an important issue in management and protection of groundwater resource,
which can be well achieved by groundwater modelling. To explain some phenomena of correlation between groundwater level and
salinity in observation wells in coastal area, the authors compare the migration velocity of saline particles and transmission
velocity of water pressure and derive analytical equations of these two velocities for plane and radial flows. The driving
force and resistance of saline intrusion were analysed based on the analytical modelling. The destruction and reconstruction
of the equilibrium between fresh water seepage towards sea and saline dispersion to inland were considered as an essence of
whole intrusion process. The dynamic process of seepage and dispersion at different stages of saline intrusion were analysed
under groundwater over-exploitation. The basic equations of saline intrusion were derived and the mechanism of transitional
zone movement was discussed. These constitute coupled seepage–dispersion theory of saline intrusion, which becomes an important
supplement to existing theory of saline intrusion. As a case study on saline intrusion in Guangrao County in Eastern China,
this theory was applied to predict the development of saline intrusion in the study area. 相似文献
2.
Origin and distribution of saline groundwaters in the upper Miocene aquifer system, coastal Rhodope area, northeastern Greece 总被引:6,自引:3,他引:3
This paper describes the origins and distribution of saline groundwaters in the coastal area of Rhodope, Greece. The aquifer
system includes two aquifers within coarse-grained alluvial sediments in the coastal part of the study area. Two major water-quality
groups occur in the study area, namely Ca2+-rich saline groundwater and Ca2+-poor, almost fresh groundwater. The main process controlling the groundwater chemistry is the exchange of calcium and sodium
between the aquifer matrix and intruding seawater. The natural salt water in the study area is probably residual water that
infiltrated the aquifer system during repeated marine transgressions in late Pleistocene time. Seawater intrusion into the
coastal aquifer system occurs as a result of overpumping in two seawater wedges separated vertically by a low-permeability
layer. The rate of intrusion averages 0.8 m/d and is less than expected due to a decline of the aquifer's permeability at
the interface with the seawater. The application of several hydrochemical techniques (Piper and Durov diagrams; Na+/Cl–, Ca2+/Cl–, Mg2+/Cl–, and Br–/Cl– molar ratios; Ca2+/Mg2+ weight ratio; and chloride concentrations), combined with field observations, may lead to a better explanation of the origin
of the saline groundwater.
Received, May 1997 / Revised, May 1998, December 1998 / Accepted, February 1999 相似文献
3.
One-third of the population of Oman depends upon groundwater extracted from the alluvium of the Batinah Plain, on the coast
of the Gulf of Oman. Deep geophysical exploration techniques were used to determine the depth and nature of the alluvium and
the boundaries of the aquifer. The base and structural controls of the alluvial basin at its contact with Tertiary marine
sediments and Cretaceous ophiolite were mapped with seismic reflection data, recorded originally for oil exploration. The
base of the alluvium dips northward from the foothills of the Northern Oman Mountains, reaching a maximum depth of 2000 m
at the coast. The varying facies of the alluvium are grossly characterised by different, overlapping ranges of electrical
resistivity, depending largely on the clay content and degree of cementation. Resistivities near the coast are reduced by
saline intrusion. These variations of resistivity were mapped with time-domain electromagnetic sounding along 400 km of profile,
to distinguish among the three zones of the alluvial aquifer. The wedge of saline intrusion was also delineated, up to 10 km
from the coast. The thickness of the saturated gravel aquifer ranges from 20–160 m in an area greater than 600 km2.
Received, April 1997 · Revised, January 1998 · Accepted, April 1998 相似文献
4.
Determining groundwater protection zones for the Quaternary aquifer of northeastern Nile Delta using GIS-based vulnerability mapping 总被引:3,自引:2,他引:1
Hossam H. Elewa Ragaa E. Shohaib Atef A. Qaddah Ahmad M. Nousir 《Environmental Earth Sciences》2013,68(2):313-331
The area of study lies at the northeastern part of Nile Delta. Global shoreline regression and sea-level rise have their own-bearing on the groundwater salinization due to seawater intrusion. A new adopted approach for vulnerability mapping using the hydrochemical investigations, geographic information system and a weighted multi-criteria decision support system (WMCDSS) was developed to determine the trend of groundwater contamination by seawater intrusion. Six thematic layers were digitally integrated and assigned different weights and rates. These have been created to comprise the most decisive criteria used for the delineation of groundwater degradation due to seawater intrusion. These criteria are represented by the total dissolved solids, well discharge, sodium adsorption ratio, hydrochemical parameter (Cl/HCO3), hydraulic conductivity and water types. The WMCDSS modeling was tried, where a groundwater vulnerability map with four classes ranging from very low to high vulnerability was gained. The map pinpointed the promising localities for groundwater protection, which are almost represented by the very low or low vulnerability areas (53.69 % of the total study area). The regions having high and moderate groundwater vulnerability occupy 46.31 % of total study area, which designate to a deteriorated territory of groundwater quality, and needs special treatment and cropping pattern before use. However, the moderate groundwater vulnerability class occupies an area of about 28.77 % of the total mapped area, which highlighted the need for certain management practices to prevent the saltwater intrusion from expanding further to the south. There was a good correlation of the constructed vulnerability map with the recently gathered water quality data and hydrochemical facies evolution. The plotting of water quality data on Piper trilinear diagram revealed the evolution of freshwater into the mixing and the saline zones as an impact of seawater intrusion, which validates the model results. 相似文献
5.
Simulation of seawater intrusion into the Khan Yunis area of the Gaza Strip coastal aquifer 总被引:4,自引:3,他引:1
The Gaza Strip coastal aquifer is under severe hydrological stress due to over-exploitation. Excessive pumping during the
past decades in the Gaza region has caused a significant lowering of groundwater levels, altering in some regions the normal
transport of salts into the sea and reversing the gradient of groundwater flow. The sharp increase in chloride concentrations
in groundwater indicates intrusion of seawater and/or brines from the western part of the aquifer near the sea.
Simulations of salt-water intrusion were carried out using a two-dimensional density-dependent flow and transport model SUTRA
(Voss 1984). This model was applied to the Khan Yunis section of the Gaza Strip aquifer. Simulations were done under an assumption
that pumping rates increase according to the rate of population growth, or about 3.8% a year. Model parameters were estimated
using available field observations. Numerical simulations show that the rate of seawater intrusion during 1997–2006 is expected
to be 20–45 m/yr. The results lead to a better understanding of aquifer salinization due to seawater intrusion and give some
estimate of the rate of deterioration of groundwater.
Received, September 1997 Revised, January 1998, July 1998 Accepted, August 1998 相似文献
6.
Marine contamination of groundwater may be caused by seawater intrusion and by salt spray. The role of both processes was
studied in the Cyclades archipelago on four small islands (45–195 km2) whose aquifers consist essentially of fractured, weathered metamorphic rocks. Annual rainfall ranges from 400 to 650 mm
and precipitation has high total dissolved solids contents of 45–223 mg l–1. The chemical characteristics of the groundwater, whose salinity is from 0.4 to 22 g l–1, are strongly influenced by seawater intrusion. However, the effect of atmospheric input is shown in certain water sampling
locations on high ground elevation where the dissolved chloride contents may attain 200 mg l–1.
Received: 14 November 1995 · Accepted: 9 September 1996 相似文献
7.
Salt-water discharges from a fault system in the crystalline basement of the Black Forest into the gravel aquifer of the
Kinzig River valley near Ohlsbach, upper Rhine River valley, southwestern Germany. The salt water (TDS, 16 g/kg) ascends from
a reservoir at 1 3 km depth. Once discharged into the gravel aquifer, the saline deep water mixes with fresh groundwater
and is carried along the groundwater flow path to the middle of the Rhine River valley. There, the natural geogene salt-water
plume merges with a man-made chloride-rich infiltration zone along the Rhine River. The plume was mapped using (1) chloride
data from groundwater observation wells, and (2) resistivity data from geoelectric sounding. Background chloride is about
7 mg/kg. In the central region of the plume, chloride concentration exceeds 200 mg/kg. A continuous area of Cl 1 50 mg/kg
is distinguished from the discharge fault to the Rhine River over a distance of 12 km. Resistivities range from 1 50 Ω in
uncontaminated regions to <7 Ω in the 700 m-long central region of the plume. A low resistivity plume (7–10 Ω) stretches for
1 7 km into the Rhine River valley. The two plume maps are in good agreement.
Received, April 1998 / Revised, November 1998, January 1999 / Accepted, January 1999 相似文献
8.
M. Mazari-Hiriart C. Hernández-Eugenio F. Rojo-Callejas R. Lozano-Santacruz 《Environmental Geology》2000,39(6):595-602
A surficial clay aquitard extends through the urban area where Mexico City is located. It has been assumed to function as
a protective layer to the underlying aquifer that provides 42 m3/s out of 63 m3/s of water used by 18 million inhabitants. To provide such protection, the aquitard must be impermeable to water flow and,
ideally, have a significant capacity to sorb contaminants. The latter aspect was addressed, studying the vertical variability
of sorption of perchloroethylene (PCE), a widely used organic compound considered to pose health risks in groundwater. Batch
sorption tests were used and the clay-rich strata in the depth interval from 8 to 75 m were studied. The results suggest that
sorption depends mainly on the fraction of organic carbon (foc) present in the clayey materials. The sorption data were fit to the linear and Freundlich models; many strata could be fit
well by either model, while some strata were distinctly non-linear. The linear isotherms showed a mean value of 32.8 ml/g,
and the Freundlich isotherm 96.6 ml/g, confirming that the clay-rich media have significant sorption capacity for PCE. From
the environmental perspective the clay-rich materials are serving as protection to the groundwater system.
Received: 2 November 1998 · Accepted: 15 February 1999 相似文献
9.
Study of shallow groundwater quality evolution under saline intrusion with environmental isotopes and geochemistry 总被引:2,自引:0,他引:2
Evolution of the shallow groundwater quality under saline intrusion in porous aquifer system has been studied with environmental
isotopes and geochemistry in the Laizhou Bay area, China. Two campaigns of water sampling from various sources were carried
out in spring and winter for environmental isotopic and chemical analyses. The origin of groundwater salinity from intrusion
of both modern seawater and deep brine water was identified by analysing the correlations between 18O, D, T, Cl−, SO42− and electrical conductivity. The results indicate that the brine is originated from evaporating and concentrating of intruded
seawater and its δD and δ18O are different from modern seawater but similar to those of mixture of seawater with fresh groundwater. It is hard to distinguish
the salinity origin in this area by the δD–δ18O relationship alone. The relations between δ18O and conductivity, Cl− and SO42− have been used to identify the salinity origin due to the distinct difference in salinity between the brine and seawater,
conjunctively with use of T. A threshold of T = 12 TU was adopted to identify the origin of saline groundwater. 相似文献
10.
Geochemical mixing models were used to decipher the dominant source of freshwater (rainfall, canal discharge, or groundwater
discharge) to Biscayne Bay, an estuary in south Florida. Discrete samples of precipitation, canal water, groundwater, and
bay surface water were collected monthly for 2 years and analyzed for salinity, stable isotopes of oxygen and hydrogen, and
Sr2+/Ca2+ concentrations. These geochemical tracers were used in three separate mixing models and then combined to trace the magnitude
and timing of the freshwater inputs to the estuary. Fresh groundwater had an isotopic signature (δ
18O = −2.66‰, δD −7.60‰) similar to rainfall (δ
18O = −2.86‰, δD = −4.78‰). Canal water had a heavy isotopic signature (δ
18O = −0.46‰, δD = −2.48‰) due to evaporation. This made it possible to use stable isotopes of oxygen and hydrogen to separate canal water
from precipitation and groundwater as a source of freshwater into the bay. A second model using Sr2+/Ca2+ ratios was developed to discern fresh groundwater inputs from precipitation inputs. Groundwater had a Sr2+/Ca2+ ratio of 0.07, while precipitation had a dissimilar ratio of 0.89. When combined, these models showed a freshwater input
ratio of canal/precipitation/groundwater of 37%:53%:10% in the wet season and 40%:55%:5% in the dry season with an error of
±25%. For a bay-wide water budget that includes saltwater and freshwater mixing, fresh groundwater accounts for 1–2% of the
total fresh and saline water input. 相似文献
11.
Hydrogeochemical analysis and evaluation of groundwater quality in the Gadilam river basin,Tamil Nadu,India 总被引:2,自引:0,他引:2
M V PRASANNA S CHIDAMBARAM A SHAHUL HAMEED K SRINIVASAMOORTHY 《Journal of Earth System Science》2011,120(1):85-98
Water samples were collected from different formations of Gadilam river basin and analyzed to assess the major ion chemistry
and suitability of water for domestic and drinking purposes. Chemical parameters of groundwater such as pH, electrical conductivity
(EC), total dissolved solids (TDS), Sodium (Na + ), Potassium (K + ), Calcium (Ca + ), Magnesium (Mg + ), Bicarbonate (HCO3 -_{3}^{\ \,-}), Sulphate (SO4 -_{4}^{\ \,-}), Phosphate (PO4 -_{4}^{\ \,-}) and Silica (H4SiO4) were determined. The geochemical study of the aquatic systems of the Gadilam river basin show that the groundwater is near-acidic
to alkaline and mostly oxidizing in nature. Higher concentration of Sodium and Chloride indicates leaching of secondary salts
and anthropogenic impact by industry and salt water intrusion. Spatial distribution of EC indicates anthropogenic impact in
the downstream side of the basin. The concentration levels of trace metals such as Iron (Fe), Lead (Pb), Nickel (Ni), Bromide
(Br), Iodide (I) and Aluminium (Al) have been compared with the world standard. Interpretation of data shows that some trace
metals such as Al, Ni and Pb exceed the acceptable limit of world standard. Geophysical study was carried out to identify
the weathered zone in the hard rock and contaminated zone by anthropogenic impact in the downstream of river Gadilam. A few
of the groundwater samples in the study area were found to be unsuitable for domestic and drinking purposes. 相似文献
12.
MENG Yong-hui WANG Ji-ning YU De-Jie ZHANG Li-xia FENG Zai-min YAN Tang ZHOU Yong 《地下水科学与工程》2014,7(3):245-252
Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level, this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area. According to monitoring data of groundwater quality, the distribution characteristics of macro component are analyzed, and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment. Concerning the influence degree of groundwater environment, the study area is divided into brine area, seriously influenced area, moderately influenced zone, slightly influenced zone and uninfluenced zone. The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources. 相似文献
13.
MENG Yong-hui WANG Ji-ning YU De-Jie ZHANG Li-xia FENG Zai-min YAN Tang ZHOU Yong 《地下水科学与工程》2019,(3):245-252
Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level,this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area.According to monitoring data of groundwater quality,the distribution characteristics of macro component are analyzed,and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment.Concerning the influence degree of groundwater environment,the study area is divided into brine area,seriously influenced area,moderately influenced zone,slightly influenced zone and uninfluenced zone.The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources. 相似文献
14.
National scale evaluation of groundwater chemistry in Korea coastal aquifers: evidences of seawater intrusion 总被引:3,自引:2,他引:1
Youngyun Park Jin-Yong Lee Jeong-Hee Kim Sung-Ho Song 《Environmental Earth Sciences》2012,66(3):707-718
Pollution of groundwater by seawater intrusion poses a threat to sustainable agriculture in the coastal areas of Korea. Therefore, seawater intrusion monitoring stations were installed in eastern, western, and southern coastal areas and have been operated since 1998. In this study, groundwater chemistry data obtained from the seawater intrusion monitoring stations during the period from 2007 to 2009 were analyzed and evaluated. Groundwater was classified into fresh (<1,500 μS/cm), brackish (1,500–3,000 μS/cm), and saline (>3,000 μS/cm) according to EC levels. Among groundwater samples (n = 233), 56, 7, and 37% were classified as the fresh, brackish, and saline, respectively. The major dissolved components of the brackish and saline groundwaters were enriched compared with those of the fresh groundwater. The enrichment of Na+ and Cl− was especially noticeable due to seawater intrusion. Thus, the brackish and saline groundwaters were classified as Ca–Cl and Na–Cl types, while the fresh groundwater was classified as Na–HCO3 and Ca–HCO3 types. The groundwater included in the Na–Cl types indicated the effects of seawater mixing. Ca2+, Mg2+, Na+, K+, SO4 2−, and Br− showed good correlations with Cl− of over r = 0.624. Of these components, the strong correlations of Mg2+, SO4 2−, and Br− with Cl− (r ≥ 0.823) indicated a distinct mixing between fresh groundwater and seawater. The Ca/Cl and HCO3/Cl ratios of the groundwaters gradually decreased and approached those of seawater. The Mg/Cl, Na/Cl, K/Cl, SO4/Cl, and Br/Cl ratios of the groundwaters gradually decreased, and were similar to or lower than those of seawater, indicating that Mg2+, Na+, K+, SO4 2−, and Br−, as well as Cl− in the saline groundwater can be enriched by seawater mixing, while Ca2+ and HCO3 − are mainly released by weathering processes. The influence of seawater intrusion was evaluated using threshold values of Cl− and Br−, which were estimated as 80.5 and 0.54 mg/L, respectively. According to these criteria, 41–50% of the groundwaters were affected by seawater mixing. 相似文献
15.
The occurrence, movement and control of groundwater, particularly in hard-rock areas, are governed by different factors such
as topography, lithology, structures like fractures, faults and nature of weathering. An attempt is made in the present study
to investigate the extent of the influence of structures such as fractures and thereby delineate the nature of subsurface
lithology with the help of an electrical resistivity method. For this study, the Upper Gunjanaeru River basin, Cuddapah district
Andhra Pradesh was chosen to determine groundwater potentials. In order to understand the significance of the fracture pattern,
geological, hydrogeomorphological and lineament maps were prepared based on the field data and also from the LANDSAT TM imagery.
Further, electrical resistivity surveys were conducted to determine the subsurface lithology and also to confirm the studies
of LANDSAT imagery. The isoresistivity contour map has been prepared based on the 45 VES conducted to determine the resistivity
variations in the study area. The isoresistivity contours obtained were found to conform to the structural trends obtained
by geological studies and also confirm the relationship between the structure and secondary porosity present in the rocks.
The lineaments in the area have two preferred directions. One set is a NE-SW direction (N 30°–70° E; S 30°–70° W) and another
is a NW-SE direction (N 0°–30° W; S 0°–30° E and N 60°–80° W; S 60°–80° E). The water-table contour map shows that the direction
of groundwater flow is south to north.
Received: 3 March 1997 · Accepted: 17 June 1997 相似文献
16.
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
17.
This paper presents a site-specific conceptual model of groundwater flow in fractured damage zones associated with faulting
in a package of sedimentary rocks. The model is based on the results of field and laboratory investigations. Groundwater and
methane gas inflows from fault-fracture systems in the West Elk coal mine, Colorado, USA, have occurred with increasing severity.
Inflows of 6, 160 and 500 L s−1 discharged almost instantaneously from three separate faults encountered in mine workings about 460 m below ground level.
The faults are about 600 m apart. The δ
2H and δ
18O compositions of the fault-related inflow waters and the hydrodynamic responses of each fault inflow indicate that the groundwaters
discharge from hydraulically isolated systems. 14C data indicate that the groundwaters are as much as 10,500 years old. Discharge temperatures are geothermal (≈30°C), which
could indicate upwelling from depth. However, calculations of geothermal gradients, analysis of solute compositions of groundwater
in potential host reservoirs, geothermometer calculations, and results of packer testing indicate that the fractured groundwater
reservoir is the Rollins Sandstone (120 m thick) directly beneath the coal seams. The packer test also demonstrates that the
methane gas is contained in the coal seams. A geothermal gradient of 70–80°C km−1, related to an underlying intrusion, is probably responsible for the slightly elevated discharge temperatures. Large discharge
volumes, as great as 8.2×105 m3 from the 14 South East Headgate fault (14 SEHG), rapid declines in discharge rates, and vertical and horizontal permeability
(matrix permeability generally <0.006 Darcy) indicate fracture flow. An in-mine pumping test demonstrates that the 14 SEHG
fault has excellent hydraulic communication with fractures 50 m from the fault. Aeromagnetic data indicate that the faults
are tectonically related to an igneous body that is several thousand meters below the coal seams. Exploratory drilling has
confirmed a fourth fault, and two additional faults are projected, based on the aeromagnetic data. The conceptual model describes
a series of parallel, hydraulically separate groundwater systems associated with fault-specific damage zones. The faults are
about 600 m apart. Groundwater stored in fractured sandstone is confined above and below by clayey layers.
Received March 1999 / Revised, November 1999 / Accepted, December 1999 相似文献
18.
Evaluation of groundwater quality in coastal areas: implications for sustainable agriculture 总被引:4,自引:1,他引:4
Seawater intrusion is a problem in the coastal areas of Korea. Most productive agricultural fields are in the western and
southern coastal areas of the country where irrigation predominantly relies on groundwater. Seawater intrusion has affected
agricultural productivity. To evaluate progressive encroachment of saline water, the Korean government established a seawater
intrusion monitoring well network, especially in the western and southern part of the peninsula. Automatic water levels and
EC monitoring and periodic chemical analysis of groundwater help track salinization. Salinization of fresh groundwater is
highly associated with groundwater withdrawal. A large proportion of the groundwaters are classified as Na–Cl and Ca–Cl types.
The Na–Cl types represent effects of seawater intrusion. The highest EC level was over 1.6 km inland and high Cl values were
observed up to 1.2 km inland. Lower ratios of Na/Cl and SO4/Cl than seawater values indicate the seawater encroachment. A linear relation between Na and Cl represents simple mixing
of the fresh groundwater with the seawater. The saline Na–Cl typed groundwaters showed Br/Cl ratios similar to or less than
seawater values. The Ca–HCO3 type groundwaters had the highest Br/Cl ratios. Substantial proportions of the groundwaters showed potential for salinity
and should be better managed for sustainable agriculture. 相似文献
19.
B. J. M. Goes 《Hydrogeology Journal》1999,7(3):294-304
The Hadejia–Nguru Wetlands are annually inundated flood plains in semi-arid northeastern Nigeria. The area has a unique ecosystem
that forms a natural barrier against the encroachment of the Sahara desert. Both the rich wetland vegetation and local farmers
using shallow tube wells depend on a groundwater mound (with a water table less than 6 m below the surface) that is present
in the unconfined aquifer under the flood-plain area. Using well records (1991–97) and a hydrogeologic profile based on piezometers
that were monitored for two years, it is shown that recharge through the annually inundated flood plains is the source of
the groundwater mound. Maintenance of the groundwater-recharge function of the flood plains depends on wet-season releases
from two large upstream dams. On the basis of a water-budget method, the mean (1991–97) wet-season unconfined groundwater
recharge in the flood-plain area between Hadejia and Nguru and in the immediate vicinity (1250 km2) is estimated to be 132 mm (range, 73–197 mm). Outflow from the unconfined flood-plain aquifer to the unconfined upland aquifer
is approximately 10% of the wet-season flood-plain recharge. The unconfined groundwater outflow from the flood-plain area
can provide a significant contribution to the present-day rural water supply in the surrounding uplands, but it does not offer
much potential for additional groundwater abstraction. In addition to outflow to the upland aquifer (∼14 mm), the distribution
of the annually recharged water volume of the shallow flood-plain aquifer is (1) domestic uses (3 mm), (2) small-scale irrigation
(∼15 mm), and (3) evapotranspiration ( 1 100 mm). Along the hydrogeologic profile, the recharge in the upland (i.e., outflow
from the unconfined flood-plain aquifer and possibly diffuse rain-fed recharge) is in balance with the water uses (i.e., domestic
uses, groundwater outflow, and evapotranspiration). The absence of a seasonal water-level trend in the two piezometers in
the upland indicates that no rain-fed recharge occurs through preferential path-way (macropore) flow.
Received, June 1998 / Revised, November 1998, January 1999 / Accepted, January 1999 相似文献
20.
Enrichment of fluoride in groundwater under the impact of saline water intrusion at the salt lake area of Yuncheng basin,northern China 总被引:2,自引:0,他引:2
Long-term intake of high-fluoride groundwater causes endemic fluorosis. This study, for the first time, discovered that the
salt lake water intrusion into neighboring shallow aquifers might result in elevation of fluoride content of the groundwater.
Two cross-sections along the groundwater flow paths were selected to study the geochemical processes controlling fluoride
concentration in Yuncheng basin, northern China. There are two major reasons for the observed elevation of fluoride content:
one is the direct contribution of the saline water; the other is the undersaturation of the groundwater with respect to fluorite
due to salt water intrusion, which appears to be more important reason. The processes of the fluorine activity reduction and
the change of Na/Ca ratio in groundwater induced by the intrusion of saline water favor further dissolution of fluorine-bearing
mineral, and it was modeled using PHREEQC. With the increase in Na concentration (by adding NaCl or Na2SO4 as Na source, calcium content kept invariable), the increase of NaF concentration was rapid at first and then became slower;
and the concentrations of HF, HF2−, CaF+, and MgF+ were continuously decreasing. The geochemical conditions in the study area are advantageous to the complexation of F− with Na+ and the decline of saturation index of CaF2, regardless of the water type (Cl–Na or SO4–Na type water). 相似文献