首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 567 毫秒
1.
《水文科学杂志》2013,58(3):441-454
Abstract

In wells tapping coastal aquifers, piezometric fluctuations can be observed in response to the ocean tide. Simultaneous recordings of the ocean tide and of the piezometric variations may provide a basis for characterizing the hydrodynamics of the aquifer. This approach was attempted to characterize the Dridrate aquifer, located on the Atlantic coast of Morocco. This aquifer accounts for most of the regional drinking water resources. However, its hydrodynamic characteristics are very poorly known. The study compares observed and simulated piezometric fluctuations, under various assumptions (confined, semi-confined aquifer). The model, which best explains the hydrodynamic behaviour of this aquifer is a semi-confined and strongly heterogeneous aquifer model (calculated hydraulic diffusivity values vary over several orders of magnitude). This result is new and rather surprising, since to date this aquifer was considered confined in view of its geological setting. Consequently, new questions are raised regarding the protection and management of the groundwater resources of this aquifer.  相似文献   

2.
Abstract

The Agua Amarga coastal aquifer has been the object of a succession of anthropogenic interventions over the last 90 years: (a) the operation of saltworks from 1925 to 1975; (b) the withdrawal, since 2003, of groundwater from the aquifer along the coast line; and (c) the programme of pouring seawater over the salt marsh, carried out since 2009, to recover the piezometric levels and the soil moisture conditions. For a better understanding of how these past and present human activities have affected the natural groundwater regime, and to validate certain hypotheses concerning the interpretation of experimental data on temperature depth profiles and piezometric and salinity changes, a numerical fluid flow and solute transport model was designed and applied to the period 1925–2010, using SEAWAT. This model reproduces, in a qualitative and quantitative way, the flow and transport processes that operated during this time, as well as the behaviour of the seawater wedge.

Citation Alhama Manteca, I., 2013. Simulation and consequences of successive anthropogenic activity in the Agua Amarga coastal aquifer (southeast Spain). Hydrological Sciences Journal, 58 (5), 1072–1087.

Editor D. Koutsoyiannis  相似文献   

3.
Hydrogeological information for the territories of the Republic of Estonia, Leningrad province, and northern Pskov province of the Russian Federation is generalized. A unified groundwater flow model was developed for the Lomonosov-Voronkovskii aquifer, including its Estonian part is developed. The methodological approaches for solving transboundary problems as applied to groundwater are determined. The results of studying transboundary hydrodynamic interaction in Lomonosov-Voronkovskii aquifer in the Russian-Estonian boundary area are given. The direction of undisturbed groundwater flow is determined, and changes caused by the exploitation of the aquifer are assessed.  相似文献   

4.
The groundwater flow in a fissured chalky environment at the northern border of the Paris Basin depends on several geological and hydrogeological parameters. Although the studied sector of the basin presents a homogeneous rock type, it is affected by a fracture network. In this type of environment, in which the permeability is low, the groundwater flow displays significant disruption, which is localized in the Fruges region (northern France). The interconnection of the discontinuities (network of fault and/or joints) is reliant on the structural control of groundwater flow through increases in the hydraulic connection between the unsaturated and the saturated zone. The methodology developed herein makes use of microstructural and regional analysis of the fracture patterns, and allowed consideration of the piezometric variations of the chalk aquifer during periods of low and high groundwater levels (April and October 2001) and a diagraphic representation of the estimated physical parameters (electrical resistivity). This enabled us to construct a ‘flow structure’ conceptual model in which we identify two types of faults: tight walls and flow paths that control the piezometric heads and the flow rate. Model validation was carried out on a similar sector. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

5.
《水文科学杂志》2013,58(4):700-712
Abstract

The groundwater flow equation governing the elevation (h) of the steady-state phreatic surface in a sloping aquifer fed by constant recharge over a bi-circular sector is rhh′ ? r 2 Bh′ + Pr 2 ? PR 2 = 0, where r is the radial coordinate, P is a constant involving recharge and aquifer properties, and B is the slope of the aquifer—bedrock boundary. The derived flow equation describes radially convergent flow through a sloping aquifer that discharges to a water body of fixed head. One important simplification is that in which the width of the bi-circular sector is constant, and the draining land becomes a rectangular aquifer. The bi-circular sector and rectangular-strip groundwater flow problems are solved in terms of implicit equations. The solutions for the steady-state phreatic surfaces depend on the ratio of recharge to hydraulic conductivity, the slope of the aquifer-bedrock, and the downstream constant-head boundary. Computational examples illustrate the application of the solutions.  相似文献   

6.
Abstract

Estimating groundwater recharge is essential to ensure the sustainable use of groundwater resources, particularly in arid and semi-arid regions. Soil water balances have been frequently advocated as valuable tools to estimate groundwater recharge. This article compares the performance of three soil water balance models (Hydrobal, Visual Balan v2.0 and Thornthwaite) in the Ventós-Castellar aquifer, Spain. The models were used to simulate wet and dry years. Recharge estimates were transformed into water table fluctuations by means of a lumped groundwater model. These, in turn, were calibrated against piezometric data. Overall, the Hydrobal model shows the best fit between observed and calculated levels (r2 = 0.84), highlighting the role of soil moisture and vegetation in recharge processes.

Editor D. Koutsoyiannis; Associate editor X. Chen

Citation Touhami, I., et al., 2014. Comparative performance of soil water balance models in computing semi-arid aquifer recharge. Hydrological Sciences Journal, 59 (1), 193–203.  相似文献   

7.
Abstract

A mathematical model for the optimal, conjunctive management of a groundwater basin's quality and quantity resources is presented. The quality resource, the assimilative waste capacity, is the ability of the aquifer to degrade certain non-conservative constituents through the actions of molecular diffusion, hydrodynamic dispersion, adsorption, biochemical reactions and convective mass transport. The model is applicable to saturated, isothermal, porous media. The Galerkin method is used to express the spatial and temporal variations in hydraulic head and constituent concentrations as a function of possible recharge, pumping, and treatment decisions. The Galerkin procedure ensures that the constraint equations actually model the response characteristics (flow and mass transport) of the groundwater basin. In each planning period, the groundwater basin is required to meet an exogenous water demand while maintaining adequate water quality levels throughout the aquifer. The model, structured as a mathematical program, minimizes the sum of waste water treatment and pumping and recharge costs. The results indicate (1) the feasibility of conjunctive management of an aquifer's quality and quantity resources, and (2) that the assimilative waste capacity can function as a form of secondary or advanced waste water treatment.  相似文献   

8.
Rapid urbanization in the Jakarta area has become a severe subsurface environmental issue as it entails groundwater level decline and land subsidence caused by excessive groundwater pumping. In this study, apparent groundwater age rejuvenation in the deep aquifer under DKI Jakarta was found by comparing 14C activities between 1985 and 2008. We discussed the use of a numerical groundwater flow model to evaluate the rejuvenation process in this urbanized area. When considering the deep aquifer in the DKI Jakarta area, we can assume six direction fluxes toward the aquifer: two vertical fluxes (downward and upward flux) and four horizontal fluxes (northern, southern, western, and eastern flux). Results of model calculations show that the greatest groundwater flux among six flux directions became ‘vertical downward flux’, which means that shallower groundwater intrudes into the deep one because of excessive groundwater pumping from the mid‐1980s. This flux grows about 50% during the 2000s. This result is consistent with the detection of CFC‐12 and SF6, which functions as an indicator of young groundwater even in the deep groundwater. The rejuvenation ratio ‘R’ was determined using 14C activity in the groundwater; R increases with the CFC‐12 concentration and both show good correlation. Furthermore, we estimated the ‘vertical downward flux’ at each well's screen depth using model estimation. Results show that this flux is greater in the urban groundwater depression area and especially at shallower parts of the deep aquifer, and that it affects the magnitude of the shallow groundwater intrusion. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

9.
Abstract

Knowledge of the processes that control nitrate migration and its geochemical evolution in the subsurface are fundamental for the regional management of polluted aquifers. In this paper, the spatial distribution and transient variations of nitrate concentrations, associated with manure fertilization, are used to depict hydrogeological dynamics within the sedimentary aquifer system of la Plana de Vic in the Osona region of Spain. Flow systems are identified from geological, hydraulic head, hydrochemical and isotopic data, and by considering nitrate itself as a tracer that indicates how flow paths are modified by human pressures. In this area, nitrates move through fractured aquitards in flows induced by groundwater pumping. Moreover, the lack of casing in the boreholes permits a mixing of groundwater from distinct layers inside the wells, which negates any benefits from the low-nitrate groundwater found in the deepest aquifer layers. Therefore, impacts on groundwater quality are related to intensive manure fertilization as well as to inadequate well construction and exploitation strategies.

Citation Menció, A., Mas-Pla, J., Otero, N. & Soler, A. (2011) Nitrate as a tracer of groundwater flow in a fractured multilayered aquifer. Hydrol. Sci. J. 56(1), 108–122.  相似文献   

10.
ABSTRACT

This paper presents a model of the groundwater flow into a river from an aquifer beneath the river. The mathematical problem is to solve Laplace's equation with a free boundary and the solution procedure uses a variational inequality which leads to an approximate solution using finite differences. The method can be used to provide for example, inflow conditions in river modelling calculations.  相似文献   

11.
Abstract

This paper describes a study of groundwater flow in a coastal Miliolite limestone aquifer in western India. An examination of field information suggested that the transmissivity of the aquifer varies significantly between high and low groundwater heads. Pumping tests indicate that this is due to the development of major fissures in the upper part of the aquifer. A regional groundwater model with varying transmissivities is used to represent the field behaviour. The model is also used to examine the effect of artificial recharge on the alleviation of saline intrusion problems in the coastal area.  相似文献   

12.
Abstract

An analytical solution is developed to delineate the capture zone of a pumping well in an aquifer with a regional flow perpendicular to a stream, assuming a leaky layer between the stream and the aquifer. Three different scenarios are considered for different pumping rates. At low pumping rates, the capture zone boundary will be completely contained in the aquifer. At medium pumping rates, the tip of the capture zone boundary will intrude into the leaky layer. Under these two scenarios, all the pumped water is supplied from the regional groundwater flow in the aquifer. At high pumping rates, however, the capture zone boundary intersects the stream and pumped water is supplied from both the aquifer and the stream. The two critical pumping rates which separate these three scenarios, as well as the proportion of pumped water from the stream and the aquifer, are determined for different hydraulic settings.

Editor D. Koutsoyiannis; Associate editor A. Koussis

Citation Asadi-Aghbolaghi, M., Rakhshandehroo, G.R., and Kompani-Zare, M., 2013. An analytical approach to capture zone delineation for a well near a stream with a leaky layer. Hydrological Sciences Journal, 58 (8), 1813–1823.  相似文献   

13.
Abstract

The effects of changes in climate on aquifer storage and groundwater flow to rivers have been investigated using an idealized representation of the aquifer/river system. The generalized aquifer/river model can incorporate spatial variability in aquifer transmissivity and is applied with parameters characteristic of Chalk and Triassic sandstone aquifers in the United Kingdom, and is also applicable to other aquifers elsewhere. The model is run using historical time series of recharge, estimated from observed rainfall and potential evaporation data, and with climate inputs perturbed according to a number of climate change scenarios. Simulations of baseflow suggest large proportional reductions at low flows from Chalk under high evaporation change scenarios. Simulated baseflow from the slower responding Triassic sandstone aquifer shows more uniform and less severe reductions. The change in hydrological regime is less extreme for the low evaporation change scenario, but remains significant for the Chalk aquifer.  相似文献   

14.
Abstract

Over-exploitation of an alluvial aquifer in India has occurred since tubewells were drilled into deeper aquifers. Field information concerning-the fall in both the water table and the piezometric heads in the deeper aquifers has been examined and a numerical model has been developed to represent a heavily exploited area. Predictions using the model suggest that the annual declines in the water table and the piezometric heads are accelerating as the water table moves into a zone having a lower specific yield. Careful monitoring of the movement of the water table is proposed.  相似文献   

15.
《水文科学杂志》2013,58(4):739-753
Abstract

The hydrodynamic behaviour of a sloped phreatic aquifer in the Tigray Highlands in northern Ethiopia is described. The aquifer is situated in the soils of a plateau on top of a basalt sequence and lies on steep slopes; the latter lead to hydraulic gradients that can cause high discharge fluxes. Distinct wet and dry seasons characterize the climate of the Tigray Highlands and recharge is absent during the dry season. Because of the fertile vertisols that have developed, the plateau is heavily cultivated and thus has great local economic, and hence social, importance. Water for land irrigation is almost exclusively delivered by rainfall, which is largely restricted to the period June—September. During the dry season, the water table drops dramatically and the aquifer drains nearly completely, under the strong gravity-driven, sustained discharges. This study strives to give insights into recharge and discharge mechanisms of the aquifer, in order to improve the effectiveness of the implemented water conservation measures.  相似文献   

16.
ABSTRACT

The hydrological response of shallow ponds to groundwater withdrawal has been of growing concern in the Doñana National Park (southern Spain) in recent decades. This study examines the role of groundwater in maintaining the hydroperiod (i.e. the hydrological regime) in the park’s main dune ponds, by quantifying the groundwater fluxes to/from them. The hydrological characterization was performed by applying different methodologies. Daily hydrological balances registered in the ponds revealed groundwater contributions ranging from 80% of the total water inflows (i.e. groundwater discharge) to a net groundwater recharge from the ponds to the aquifer, and enabled the studied water bodies to be classified as discharge or recharge systems. The recharge systems must have been influenced by the lowering of piezometric levels due to groundwater extraction for urban supply in a nearby coastal resort.  相似文献   

17.
Abstract

Major ions and stable isotopes in groundwaters of the Plio-Quaternary shallow aquifer of the Djerid oases, southern Tunisia, were investigated to elucidate the origin of groundwater recharge and the mineralization processes. It has been demonstrated that the groundwater composition is mainly controlled by the water–rock interaction, the encroachment of brines from the Chotts and the return flow of irrigation waters. The isotopically depleted groundwater samples suggest that the recharge waters derive from an old palaeoclimatic origin. However, the enriched groundwater samples reflect the presence of evaporated recharge water. Furthermore, the large negative deuterium-excess values indicate the effect of secondary evaporation processes, probably related to the return flow of irrigation waters pumped from the underlying aquifer.

Editor D. Koutsoyiannis; Associate editor E. Custodio

Citation Tarki, M., Dassi, L. and Jedoui, Y., 2012. Groundwater composition and recharge origin in the shallow aquifer of the Djerid oases, southern Tunisia: implications of return flow. Hydrological Sciences Journal, 57 (4), 790–804.  相似文献   

18.
Abstract

Despite the Sahelian drought of the 1970s–1990s, the unconfined aquifer in southwest Niger exhibits a multidecadal increase in groundwater reserves. Recent changes in land surface conditions have enhanced runoff and thus indirect groundwater recharge below endorheic ponds. This paper presents a model-based investigation of surface runoff and groundwater recharge at mesoscale (～5000 km2). A new lumped-conceptual runoff model applicable to the large number of ungauged endorheic catchments is specially developed, derived from an existing fine-scale, physically-based hydrologic model. Runoff simulated for sites identified as groundwater recharge sources are used to derive recharge forcing for a Modflow-based model of the aquifer. The rising water table trend and its spatial distribution over the period 1992–2003 are generally well simulated, albeit smoothed year-to-year dynamics. Comparison with alternative methods of recharge estimation suggests, however, that there may presently exist more recharging sites and/or contributing surfaces than those considered so far.

Citation Massuel, S., Cappelaere, B., Favreau, G., Leduc, C., Lebel, T. & Vischel, T. (2011) Integrated surface water–groundwater modelling in the context of increasing water reserves of a regional Sahelian aquifer. Hydrol. Sci. J. 56(7), 1242–1264.  相似文献   

19.
Mexico City is situated in the Valley of Mexico on the extensive lacustrine clays that overlay highly productive aquifers of both volcanic and sedimentary origin. The Valley is closed by volcanic mountains. The natural hydraulic boundary conditions associated withe mountain ranges and their relationship to the important aquifers were studied using a two-dimensional, steady-state finite-element model in cross section. Four cross sections were analysed under hydrologic conditions existing prior to the large scale pumping of the aquifers. Factors such as bulk hydraulic conductivities and regional infiltration rates were obtained from field observations and the literature to assess location of the associated groundwater divides, and the water-table in the mountains. The modeled flow patterns are consistent with the historical hydrologic records piezometric characteristics and observed surface features of the groundwater in the Basin of Mexico. From the modeling results, the groundwater recharge in the mountains is 30–50% of the mean average precipitation. Higher and lower rates result in a flow regime that is not compatible with field observations. In general the location of the divides in the mountains is displaced towards the Valley of Mexico, which influences the groundwater budget of the Valley. The water table in places is several hundred metres below ground surface, in accordance with field observations of a very thick unsaturated zone. Before major aquifer exploitation began about 50 years ago, 40–50% of the total discharge into the Valley was by upward flow through the lacustrine deposits. The best results were obtained using a subsurface distribution of hydrostratigraphic units based on recently published geological interpretations.  相似文献   

20.
Abstract

Chemical and isotopic data of groundwater of the Upper Cretaceous aquifer in the Orontes basin, Syria, have been used to assess the groundwater geochemistry, the origin of groundwater recharge and groundwater residence time. The chemical data indicate that dissolution of evaporite minerals is the main process controlling groundwater mineralization. The composition of stable isotopes δ18O and δ2H, together with 14C activity, reflect the existence of three different groups: (a) groundwater in the Coastal Mountains with δ18O of –6.65‰, quite similar to modern-day precipitation, and high 14C (>50 pmC); (b) groundwater in the unconfined aquifer of the Hama Uplift, which has δ18O of –5.52‰ and 14C near 20 pmC, and is recharged locally; and (c) groundwater from the confined aquifer of the Homs Depression, which is characterized by more depleted δ18O,, –8.01‰, and low 14C (<7 pmC), and might be recharged in the northern piedmont of the Anti-Lebanon Mountains. The distinctive isotope signatures of the latter two groups indicate different recharge elevations and palaeoclimatic effects. The low recharge rate of the groundwater in the Hama Uplift aquifer, and the even slower recharge rate in the Homs Depression aquifer, are reflected by groundwater 14C residence times of 5 and over 22 Ka BP, respectively.

Editor D. Koutsoyiannis

Citation Al-Charideh, A., 2013. Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin (Syria). Hydrological Sciences Journal, 58 (2), 452–467.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号