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Geomorphic aspects of groundwater flow 总被引:3,自引:0,他引:3
Robert G. LaFleur 《Hydrogeology Journal》1999,7(1):78-93
The many roles that groundwater plays in landscape evolution are becoming more widely appreciated. In this overview, three
major categories of groundwater processes and resulting landforms are considered: (1) Dissolution creates various karst geometries,
mainly in carbonate rocks, in response to conditions of recharge, geologic setting, lithology, and groundwater circulation.
Denudation and cave formation rates can be estimated from kinetic and hydraulic parameters. (2) Groundwater weathering generates
regoliths of residual alteration products at weathering fronts, and subsequent exhumation exposes corestones, flared slopes,
balanced rocks, domed inselbergs, and etchplains of regional importance. Groundwater relocation of dissolved salts creates
duricrusts of various compositions, which become landforms. (3) Soil and rock erosion by groundwater processes include piping,
seepage erosion, and sapping, important agents in slope retreat and headward gully migration. Thresholds and limits are important
in many chemical and mechanical groundwater actions. A quantitative, morphometric approach to groundwater landforms and processes
is exemplified by selected studies in carbonate and clastic terrains of ancient and recent origins.
Received, May 1998 · Revised, September 1998 · Accepted, October 1998 相似文献
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The Heretaunga Plains, Hawke's Bay, New Zealand, is underlain by Quaternary fluvial, estuarine-lagoonal, and marine deposits
infilling a subsiding syncline. Within the depositional sequence, river-channel gravels form one of the most important aquifer
systems in New Zealand. An interconnected unconfined–confined aquifer system contains groundwater recharged from the Ngaruroro
River bed at the inland margin of the plain, 20 km from the coast. At the coast, gravel aquifers extend to a depth of 250 m.
In 1994–95, 66 Mm3 of high quality groundwater was abstracted for city and rural water supply, agriculture, industry, and horticulture. Use
of groundwater, particularly for irrigation, has increased in the last 5 years. Concern as to the sustainability of the groundwater
resource led to a research programme (1991–96). This paper presents the results and recommends specific monitoring and research
work to refine the groundwater balance, and define and maintain the sustainable yield of the aquifer system. Three critical
management factors are identified. These are (1) to ensure maintenance of consistent, unimpeded groundwater recharge from
the Ngaruroro River; (2) to specifically monitor groundwater levels and quality at the margins of the aquifer system, where
transmissivity is <5000 m2/d and summer groundwater levels indicate that abstraction exceeds recharge; (3) to review groundwater-quality programs to
ensure that areas where contamination vulnerability is identified as being highest are covered by regular monitoring.
Received, January 1998 / Revised, August 1998, March 1999 / Accepted, April 1999 相似文献
5.
Relation of streams, lakes, and wetlands to groundwater flow systems 总被引:14,自引:10,他引:14
Thomas C. Winter 《Hydrogeology Journal》1999,7(1):28-45
Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all
landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts. Although
it generally is assumed that topographically high areas are groundwater recharge areas and topographically low areas are groundwater
discharge areas, this is true primarily for regional flow systems. The superposition of local flow systems associated with
surface-water bodies on this regional framework results in complex interactions between groundwater and surface water in all
landscapes, regardless of regional topographic position. Hydrologic processes associated with the surface-water bodies themselves,
such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of
surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface
water. These processes have been documented at research sites in glacial, dune, coastal, mantled karst, and riverine terrains.
Received, April 1998 · Revised, July 1998, August 1998 · Accepted, September 1998 相似文献
6.
The Dawu well field, one of the largest in China, supplies most of the water for the Zibo City urban area in Shandong Province.
The field yields 522,400–535,400 m3/d from an aquifer in fractured karstic Middle Ordovician carbonate rocks. Much of the recharge to the aquifer is leakage
of surface water from Zihe Stream, the major drainage in the area. Installation of the Taihe Reservoir in 1972 severely reduced
the downstream flow in Zihe Stream, resulting in a marked reduction in the water table in the Dawu field. Since 1994, following
the installation of a recharge station on Zihe Stream upstream from the well field that injects water from the Taihe Reservoir
into the stream, the groundwater resources of the field have recovered. An average of 61.2×103 m3/d of groundwater, mostly from the Ordovician aquifer, is pumped from the Heiwang iron mine, an open pit in the bed of Zihe
Stream below the Taihe Reservoir. A stepwise regression equation, used to evaluate the role of discharge from the reservoir
into the stream, confirms that reservoir water is one of the major sources of groundwater in the mine.
Received, May 1998 / Revised, May 1999 / Accepted, June 1999 相似文献
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Estimation of groundwater recharge using the chloride mass-balance method, Pingtung Plain, Taiwan 总被引:4,自引:0,他引:4
Due to rapid economic growth in the Pingtung Plain of Taiwan, the use of groundwater resources has changed dramatically.
Over-pumping of the groundwater reservoir, which lowers hydraulic heads in the aquifers, is not only affecting the coastal
area negatively but has serious consequences for agriculture throughout the plain. In order to determine the safe yield of
the aquifer underlying the plain, a reliable estimate of groundwater recharge is desirable. In the present study, for the
first time, the chloride mass-balance method is adopted to estimate groundwater recharge in the plain. Four sites in the central
part were chosen to facilitate the estimations using the ion-chromatograph and Thiessen polygon-weighting methods. Based on
the measured and calculated results, in all sites, including the mountain and river boundaries, recharge to the groundwater
is probably 15% of the annual rainfall, excluding recharge from additional irrigation water. This information can improve
the accuracy of future groundwater-simulation and management models in the plain.
Received, April 1996 Revised, March 1997, November 1997 Accepted, March 1998 相似文献
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Environmental isotopes in determining groundwater flow systems, northern part of Epirus, Greece 总被引:2,自引:0,他引:2
On the basis of the isotopic composition of water in the northern part of Epirus, Greece, from springs at different altitudes with well-defined recharge areas, the altitude effect on the δ18O value of groundwater is –0.142±0.003ö (100?m)–1 and is uniform over the entire study area. Using the δ18O composition of surface water and groundwaters, the contribution of Ioannina Lake and the channel draining the lake water to the Kalamas River to the recharge of springs and boreholes was confirmed and quantitatively defined. In contrast, the Voidomatis and Vikos Rivers are not sources for recharge of the big springs along their banks. However, water from the Aoos River does replenish the aquifer in the unconsolidated deposits underlying the plain of Konitsa. In addition, limestones of Senonian–Late Eocene ages, dolomites, and limestones of the "Vigles" facies are hydraulically interconnected, and the limestones of the "Pantokrator" facies are hydraulically isolated from the other carbonate formations. 相似文献
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Assessing groundwater vulnerability using travel time and specific surface area as indicators 总被引:2,自引:0,他引:2
A method for general assessment of groundwater vulnerability was developed using the concept of hydrogeological settings
by which a small-scale landscape can be represented by larger units on the map.
For accidental spills, the time available for remedial actions is crucial. Travel times to the saturated zone or to a depth
of 5 m are classified in four intervals, ranging from <1 day to > 1 yr.
Total particle surface available for retention of pollutants in the unsaturated zone is used as a semi-quantitative indicator
of vulnerability in a long-term perspective. This indicator is classified into four intervals, ranging from <1×106 m2/m2 to >25×106 m2/m2. The quality of the surfaces is not assessed. However, the absence of an intact soil profile is estimated to result in an
increase in vulnerability by one class.
Application of the methodology was demonstrated in an area south of Stockholm, Sweden. The digital geological map was processed
using GIS to delineate four defined hydrogeological settings and vulnerability classes. Compared with an existing vulnerability
map based on stratigraphic zoning, the hydrogeological settings allow a site to be interpreted in its hydrogeological context,
and the use of quantitative vulnerability indicators increase the usefulness in practical planning and management.
Received, June 1997 · Revised, February 1998 · Accepted, April 1998 相似文献
10.
The problem of soil degradation through alkalinization/salinization in an irrigated area with a semi-arid climate was examined in the inner delta of the Niger River, Mali, by the study of groundwater hydraulics and hydrochemistry in an area recharged by irrigation water. On the basis of data analysis on various scales, it is concluded that the current extent of the surface saline soils is due to a combination of three factors: (1) the existence of ancient saline soils (solonchaks) resulting from the creation of a broad sabkha west of the former course of the Niger River, now called the Fala of Molodo. These saline crusts were gradually deposited during the eastward tilting of the tectonic block that supports the Niger River; (2) the irrigation processes during the recent reflooding of the Fala of Molodo (river diversion in 1950). These used very poorly mineralized surface water but reintroduced into the alluvial groundwater system – generally of a low permeability (K=10–6?m?s–1) – salts derived from the ancient solonchaks; and (3) the redeposition of the dissolved salts on the surface due to the intense evapotranspiration linked to the present Sahelian climate. In this context, only efficient artificial draining of subsurface alluvial groundwater can eliminate most of the highly mineralized flow and thus reduce the current saline deposits. 相似文献
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Application of remote-sensing data to groundwater exploration: A case study of the Cross River State, southeastern Nigeria 总被引:12,自引:2,他引:10
The Cross River State, Nigeria, is underlain by the Precambrian-age crystalline basement complex and by rocks of Cretaceous
to Tertiary age. The exploration for groundwater in this area requires a systematic technique in order to obtain optimum results,
but the non-availability of funds and facilities has made it extremely difficult to carry out site investigations prior to
the drilling of water wells. Therefore, the failure rate is as high as 80%. In order to delineate areas that are expected
to be suitable for future groundwater development, black and white radar imagery and aerial photographs were used to define
some hydrological and hydrogeological features in parts of the study area. Lineament and drainage patterns were analysed using
length density and frequency. Lineament-length density ranges from 0.04–1.52; lineament frequency is 0.11–5.09; drainage-length
density is 0.17–0.94, and the drainage frequency is 0.16–1.53. These range of values reflect the differences in the probability
of groundwater potentials. Results were then used to delineate areas of high, medium, and low groundwater potential. Study
results also indicate that correlations exist between lineament and drainage patterns, lithology, water temperature, water
conductivity, well yield, transmissivity, longitudinal conductance, and the occurrence of groundwater.
Received, August 1994 · Revised, March 1996, June 1996 · Accepted, October 1996 相似文献
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Duke U. Ophori 《Hydrogeology Journal》1998,6(2):193-203
Flow of groundwater with variable density and viscosity was simulated at the Atikokan Research Area (ARA) in northwestern
Ontario, Canada. An empirical viscosity–concentration equation was modified to include total-dissolved-solids (TDS) data from
the ARA. The resulting equation was used successfully to estimate reasonably accurate viscosity values over the expected range
of temperature and concentration, in comparison with experimental values derived for sodium chloride solutions. A three-dimensional
finite-element code, MOTIF, developed by Atomic Energy of Canada Limited, was used in the simulations. The inclusion of the
effects of depth-increasing temperature and TDS-dependent fluid-density distribution, while maintaining only a temperature-dependent
viscosity relationship in a simulation, resulted in a more penetrative flow against expected buoyancy effects (i.e., the physics
of the system was not honored). Accounting for concentration in the viscosity equation caused water to be less penetrative
and more in accordance with the expected physics of the system. A conclusion is that fluid concentration should be considered
simultaneously in calculating the density and viscosity of a fluid during modeling of variable-density flow in areas underlain
by fluids with high TDS. Results of simulations suggest that both flow directions and magnitudes should be employed simultaneously
during the calibration of a model. Large-scale groundwater movement in the ARA may be analyzed with carefully selected vertical
no-flow boundaries. By incorporating the geothermal temperature gradient, groundwater recharge increases by 12%; thus, this
gradient plays a significant role in groundwater flow at the ARA. Variability in the fluid concentration at the ARA neither
decreases nor increases recharge into the groundwater system. The hypothesis that an isolated continuous regional flow system
may exist at depth in the ARA is not supported by these simulations.
Received, September 1996 Revised, September 1997, February 1998 Accepted, February 1998 相似文献
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Modeling alternative paths of chemical evolution of Na-HCO3-type groundwater near Oak Ridge, Tennessee, USA 总被引:2,自引:0,他引:2
This paper demonstrates that both cation exchange, a commonly invoked mechanism, and silicate hydrolysis, which is less commonly
considered, can produce Na-HCO3-type water in sedimentary rocks. Evolution of Na-HCO3 groundwater beneath the Oak Ridge Reservation, Tennessee, USA, was studied by comparing observed end-member groundwater composition
from multiport samplers to compositions generated by reaction-path geochemical models. Observed groundwater compositions could
be reproduced by either the silicate-hydrolysis model or the cation-exchange model. Secondary minerals precipitated in the
silicate-hydrolysis model are similar to those present along fractures in the shale and carbonate host rocks, and observed
molar Sr2+/Ca2+ ratios more closely resemble evolution from shale weathering. Both mechanisms should be considered to understand the evolution
of Na-HCO3 groundwater.
Received, April 1998 · Revised, January 1999 · Accepted, March 1999 相似文献
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Patterns in groundwater chemistry resulting from groundwater flow 总被引:11,自引:7,他引:11
Pieter J. Stuyfzand 《Hydrogeology Journal》1999,7(1):15-27
Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints
of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated
by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with
a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater
flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic–methanogenic,
from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater
in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15 m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500 m in the flow direction is shown to correspond with about 5000 yr of flushing since the beach barrier with
dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution
than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical
patterns, which display groundwater flow, mixing, and groundwater ages.
Received, May 1998 · Revised, August 1998 · Accepted, October 1998 相似文献
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Hans G. Machel 《Hydrogeology Journal》1999,7(1):94-107
This article provides a critical synopsis of the effects of groundwater flow on mineral diagenesis. Emphasis is placed on
those aspects and processes that change porosity and permeability in carbonate aquifers, because they are of particular importance
to human societies as sources of supplies of water for human consumption (drinking, irrigation) and of crude oil and natural
gas.
Diagenetic settings in carbonates as well as clastics are generally ill defined. This paper proposes a new comprehensive classification
of diagenetic settings into near-surface, shallow-, intermediate-, and deep-burial diagenetic settings; hydrocarbon-contaminated
plumes; and fractures. These settings are defined on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology.
This classification is applicable to all sedimentary basins.
Diagenesis is governed by various intrinsic and extrinsic factors that include thermodynamic and kinetic constraints, as well
as microstructural factors that may override the others. These factors govern diagenetic processes, such as dissolution, compaction,
recrystallization, replacement, and sulfate–hydrocarbon redox-reactions. Processes such as cementation, dissolution, and dolomitization
require significant flow of groundwater driven by an externally imposed hydraulic gradient. Other processes, such as stylolitization
and thermochemical sulfate reduction, commonly take place without significant groundwater flow in hydrologically nearly or
completely stagnant systems that are geochemically "closed."
Two major effects of groundwater flow on mineral diagenesis are enhancement and reduction of porosity and permeability, although
groundwater flow can also leave these rock properties essentially unchanged. In extreme cases, an aquifer or hydrocarbon reservoir
rock can have highly enhanced porosity and permeability due to extensive mineral dissolution, or it can be plugged up due
to extensive mineral precipitation.
Received, April 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
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Groundwater in alluvial aquifers of the Wakatipu and Wanaka basins, Central Otago, New Zealand, has a composition expressed
in equivalent units of Ca2+≫Mg2+≅Na+>K+ for cations, and HCO3
–≫SO4
2->NO3
–≅Cl– for anions. Ca2+ and HCO3
– occur on a 1 : 1 equivalent basis and account for >80% of the ions in solution. However, some groundwater has increased proportions
of Na+ and SO4
2-, reflecting a different source for this water.
The rock material of the alluvial aquifers of both basins is derived from the erosion and weathering of metamorphic Otago
Schist (grey and green schists). Calcite is an accessory mineral in both the grey and green schists at <5% of the rock. Geological
mapping of both basins indicates that dissolution of calcite from the schist is the only likely mechanism for producing groundwater
with such a constant composition dominated by Ca2+ and HCO3
– on a 1 : 1 equivalent basis. Groundwater with higher proportions of Na+ and SO4
2- occurs near areas where the schist crops out at the surface, and this groundwater represents deeper and possibly older water
derived from basement fluids. Anomalously high K+ in the Wakatipu basin and high NO3
– concentrations in the Wanaka basin cannot be accounted for by interaction with basement lithologies, and these concentrations
probably represent the influence of anthropogenic sources on groundwater composition.
Received, June 1996 Revised, March 1997, July 1997 Accepted, July 1997 相似文献
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Contributions of groundwater conditions to soil and water salinization 总被引:21,自引:2,他引:21
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or
human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration,
hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction
of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition.
These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden
in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In
all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a
small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater
flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges
in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region,
Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction
with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas
or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path
and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed
trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate
precipitation and dissolution of capillary salts.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
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The supraregional GIS-supported stochastical model, WEKU, for the determination of groundwater residence times in the upper
aquifers of large groundwater provinces is presented. Using a two-dimensional analytical model of groundwater flow, groundwater
residence times are determined within two extreme cases. In the first case, maximal groundwater residence times are calculated,
representing the part of groundwater, that is drained by the main surface water of a groundwater catchment area. In the second
case, minimal groundwater residence times for drainage into the nearest surface water are determined. Using explicit distribution
functions of the input parameters, mean values as well as potential ranges of variations of the groundwater residence times
are derived. The WEKU model has been used for the determination of groundwater residence times throughout Germany. The model
results – mean values and deviations of the groundwater velocity and the maximal and minimal groundwater residence times in
the upper aquifers – are presented by general maps and discussed in detail. It is shown that the groundwater residence times
in the upper aquifer vary regionally, differentiated between less than 1 year and more than 2000 years. Using this information,
the time scales can be specified, until measures to remediate polluted groundwater resources may lead to a substantial groundwater
quality improvement in the different groundwater provinces of Germany. With respect to its supraregional scale of application,
the WEKU model may serve as a useful tool for the supraregional groundwater management on a state, federal or international
level.
Received: 15 August 1995 · Accepted: 15 October 1995 相似文献