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1.
Analytical solutions for the water table and lateral discharge in a heterogeneous unconfined aquifer with time-dependent source and fluctuating river stage were derived and compared with those in an equivalent homogeneous aquifer. The heterogeneous aquifer considered consists of a number of sections of different hydraulic conductivity values. The source term and river stage were assumed to be time-dependent but spatially uniform. The solutions derived is useful in studying various groundwater flow problems in a horizontally heterogeneous aquifer since the spatially piecewise-constant hydraulic conductivity and temporally piecewise-constant recharge and lateral discharge can be used to quantify variations in these processes commonly observed in reality. Applying the solutions derived to an aquifer of three sections of different hydraulic conductivity values shown that (1) the aquifer heterogeneity significantly increases the spatial variation of the water table and thus its gradient but it has little effect on lateral discharge in the case of temporally and spatially uniform recharge, (2) the time-dependent but spatially uniform recharge increases the temporal variation of groundwater table over the entire aquifer but its effect on lateral discharge is limited in the zone near the river, and (3) the effect of river stage fluctuation on the water table and lateral discharge is limited in the zone near the river and the effect of the heterogeneity is to increase lateral discharge to or recharge from the river.  相似文献   

2.
Groundwater recharge and mounding of water‐table is a complex phenomenon involving time‐ and space‐dependent hydrologic processes. The effect of long‐term groundwater mounding in the aquifer depends on soil, aquifer geometry and the area contributing to recharge. In this paper, a GIS‐based spatio‐temporal algorithm has been developed for the groundwater mound dynamics to estimate the potential rise in the water‐table and groundwater volume balance residual in an unconfined aquifer. The recharge and mound dynamics as predicted using the methodology recommended here were compared with those using the Hantush equation, and the differences were quite significant. The significance of the study is to assess the effectiveness of the basin in terms of its hydrologic and hydraulic properties for sustainable management of groundwater recharge. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3.
In Belgium, IWVA uses managed aquifer recharge (MAR) to recharge the aquifer with treated wastewater generated from the communities to sustain the potable water supply on the Belgian coast. This MAR facility is faced with a challenge of reduced infiltration rates during the winter season when pond water temperatures near 4°C. This study involves the identification of the predominant factor influencing the rate of infiltration through the pond bed. Several factors, including pumping rates, natural recharge, tidal influences of the North Sea and pond-water temperature, were identified as potential causes for variation of the recharge rate. Correlation statistics and linear regression analysis were used to determine the sensitivity of the infiltration rate to the aforementioned factors. Two groundwater flow models were developed in visual MODFLOW to simulate the water movement under the pond bed and to obtain the differences in flux to track the effects of variation of hydraulic conductivity during the two seasons. A 32% reduction in vertical hydraulic gradient in the top portion of the aquifer was observed in winter, causing the recharge rates to fluctuate. Results showed that water temperature caused a 30% increase in hydraulic conductivity in summer as compared with winter and has the maximum impact on infiltration rate. Cyclic variations in water viscosity, occurring because of seasonal temperature changes, influence the saturated hydraulic conductivity of the pond bed. Results from the models confirm the impact on infiltration rate by temperature-influenced hydraulic conductivity.  相似文献   

4.
The effects of surface water flow system changes caused by constructing water‐conservation areas and canals in southeast Florida on groundwater quality under the Atlantic Coastal Ridge was investigated with numerical modeling. Water quality data were used to delineate a zone of groundwater with low total dissolved solids (TDS) within the Biscayne aquifer under the ridge. The delineated zone has the following characteristics. Its location generally coincides with an area where the Biscayne aquifer has high transmissivities, corresponds to a high recharge area of the ridge, and underlies a part of the groundwater mound formed under the ridge prior to completion of the canals. This low TDS groundwater appears to be the result of pre‐development conditions rather than seepage from the canals constructed after the 1950s. Numerical simulation results indicate that the time for low TDS groundwater under the ridge to reach equilibrium with high TDS surface water in the water‐conservation areas and Everglades National Park are approximately 70 and 60 years, respectively. The high TDS groundwater would be restricted to the water‐conservation areas and the park due to its slow eastward movement caused by small hydraulic gradients in Rocky Glades and its mixing with the low TDS groundwater under the high‐recharge area of the ridge. The flow or physical boundary conditions such as high recharge rates or low hydraulic conductivity layers may affect how the spatial distribution of groundwater quality in an aquifer will change when a groundwater flow system reaches equilibrium with an associated surface water flow system.  相似文献   

5.
The parallel physically-based surface–subsurface model PARFLOW was used to investigate the spatial patterns and temporal dynamics of river–aquifer exchange in a heterogeneous alluvial river–aquifer system with deep water table. Aquifer heterogeneity at two scales was incorporated into the model. The architecture of the alluvial hydrofacies was represented based on conditioned geostatistical indicator simulations. Subscale variability of hydraulic conductivities (K) within hydrofacies bodies was created with a parallel Gaussian simulation. The effects of subscale heterogeneity were investigated in a Monte Carlo framework. Dynamics and patterns of river–aquifer exchange were simulated for a 30-day flow event. Simulation results show the rapid formation of saturated connections between the river channel and the deep water table at preferential flow zones that are characterized by high conductivity hydrofacies. Where the river intersects low conductivity hydrofacies shallow perched saturated zones immediately below the river form, but seepage to the deep water table remains unsaturated and seepage rates are low. Preferential flow zones, although only taking up around 50% of the river channel, account for more than 98% of total seepage. Groundwater recharge is most efficiently realized through these zones. Subscale variability of Ksat slightly increased seepage volumes, but did not change the general seepage patterns (preferential flow zones versus perched zones). Overall it is concluded that typical alluvial heterogeneity (hydrofacies architecture) is an important control of river–aquifer exchange in rivers overlying deep water tables. Simulated patterns and dynamics are in line with field observations and results from previous modeling studies using simpler models. Alluvial heterogeneity results in distinct patterns and dynamics of river–aquifer exchange with implications for groundwater recharge and the management of riparian zones (e.g. river channel-floodplain connectivity via saturated zones).  相似文献   

6.
The article presents semi‐analytical mathematical models to asses (1) enhancements of seepage from a canal and (2) induced flow from a partially penetrating river in an unconfined aquifer consequent to groundwater withdrawal in a well field in the vicinity of the river and canal. The nonlinear exponential relation between seepage from a canal reach and hydraulic head in the aquifer beneath the canal reach is used for quantifying seepage from the canal reach. Hantush's (1967) basic solution for water table rise due to recharge from a rectangular spreading basin in absence of pumping well is used for generating unit pulse response function coefficients for water table rise in the aquifer. Duhamel's convolution theory and method of superposition are applied to obtain water table position due to pumping and recharge from different canal reaches. Hunt's (1999) basic solution for river depletion due to constant pumping from a well in the vicinity of a partially penetrating river is used to generate unit pulse response function coefficients. Applying convolution technique and superposition, treating the recharge from canal reaches as recharge through conceptual injection wells, river depletion consequent to variable pumping and recharge is quantified. The integrated model is applied to a case study in Haridwar (India). The well field consists of 22 pumping wells located in the vicinity of a perennial river and a canal network. The river bank filtrate portion consequent to pumping is quantified.  相似文献   

7.
Design of managed aquifer recharge (MAR) for augmentation of groundwater resources often lacks detailed data, and simple diagnostic tools for evaluation of the water table in a broad range of parameters are needed. In many large‐scale MAR projects, the effect of a regional aquifer base dip cannot be ignored due to the scale of recharge sources (e.g., wadis, streams, reservoirs). However, Hantush's (1967) solution for a horizontal aquifer base is commonly used. To address sloping aquifers, a new closed‐form analytical solution for water table mound accounts for the geometry and orientation of recharge sources at the land surface with respect to the aquifer base dip. The solution, based on the Dupiuit‐Forchheimer approximation, Green's function method, and coordinate transformations is convenient for computing. This solution reveals important MAR traits in variance with Hantush's solution: mounding is limited in time and space; elevation of the mound is strongly affected by the dip angle; and the peak of the mound moves over time. These findings have important practical implications for assessment of various MAR scenarios, including waterlogging potential and determining proper rates of recharge. Computations are illustrated for several characteristic MAR settings.  相似文献   

8.
Xi Chen  Xunhong Chen   《Journal of Hydrology》2003,280(1-4):246-264
During a flood period, stream-stage increases induce infiltration of stream water into an aquifer; subsequent declines in stream stage cause a reverse motion of the infiltrated water. This paper presents the results of the water exchange rate between a stream and aquifer, the storage volume of the infiltrated stream water in the surrounding aquifer (bank storage), and the storage zone. The storage zone is the part of aquifer where groundwater is replaced by stream water during the flood. MODFLOW was used to simulate stream–aquifer interactions and to quantify rates of stream infiltration and return flow. MODPATH was used to trace the pathlines of the infiltrated stream water and to determine the size of the storage zone. Simulations were focused on the analyses of the effects of the stream-stage fluctuation, aquifer properties, the hydraulic conductivity of streambed sediments, regional hydraulic gradients, and recharge and evapotranspiration (ET) rates on stream–aquifer interactions. Generally, for a given stream–aquifer system, larger flow rates result from larger stream-stage fluctuations; larger storage volumes and storage zones are produced by larger and longer-lasting fluctuations. For a given stream-stage hydrograph, a lower-permeable streambed, an aquitard, or an anisotropic aquifer of low vertical hydraulic conductivity can significantly reduce the rate of infiltration and limit the size of the storage zone. The bank storage solely caused by the stage fluctuation differs slightly between gaining and losing streams. Short-term rainfall recharge and ET loss in the shallow groundwater slightly influence on the flow rate, but their effects on bank storage in a larger area for a longer period can be considerable.  相似文献   

9.
In this second of two papers, analytical step-response functions, developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to stream-stage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream–aquifer systems in the northeastern and central United States. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties, recharge rates, streambank seepage rates, and bank storage. Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield). This finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe, where sediment pores are saturated by tension, extends to land surface. Under this condition, the aquifer's response is determined by elastic storage only. Estimates of horizontal and vertical hydraulic conductivity, specific yield, specific storage, and recharge for a water-table aquifer adjacent to the Cedar River in eastern Iowa, determined by the use of analytical methods, are in close agreement with those estimated by use of a more complex, multilayer numerical model of the aquifer. Streambank leakance of the semipervious streambank materials also was estimated for the site. The streambank-leakance parameter may be considered to be a general (or lumped) parameter that accounts not only for the resistance of flow at the river–aquifer boundary, but also for the effects of partial penetration of the river and other near-stream flow phenomena not included in the theoretical development of the step-response functions.  相似文献   

10.
《水文科学杂志》2013,58(2):338-351
Abstract

A drain spacing formula is derived considering the variation in radial flux and the area above the drain level in the radial flow zone. The extent of the radial flow zone is ascertained by applying a mass balance and differentiability criterion of the water surface profile at the interface of radial and Dupuit-Forchheimer flow zones. The radial flow zone extends from the centre of the tile drain a distance of 2/π times the depth to impervious layer below the drain. For a normal ratio of recharge rate to hydraulic conductivity (R/K ≤ 0.0025), the water surface profile in the radial flow zone computed using Hooghoudt's formula is very different from the profile obtained by the new drain spacing formula; however, Hooghoudt's formula computes the maximum water table height which marginally differs from that found by the present method. For a ratio of high recharge rate to hydraulic conductivity (R/K = 0.1) and close drain spacing (L/D = 2), the difference in the maximum heights is 21%. Hooghoudt's formula overestimates the maximum water table position for L/D < 40. Unlike Hooghoudt's equivalent depth, the equivalent depth obtained using the present method is a function of the ratio of recharge rate to hydraulic conductivity.  相似文献   

11.
Simulating groundwater flow in basin‐fill aquifers of the semiarid southwestern United States commonly requires decisions about how to distribute aquifer recharge. Precipitation can recharge basin‐fill aquifers by direct infiltration and transport through faults and fractures in the high‐elevation areas, by flowing overland through high‐elevation areas to infiltrate at basin‐fill margins along mountain fronts, by flowing overland to infiltrate along ephemeral channels that often traverse basins in the area, or by some combination of these processes. The importance of accurately simulating recharge distributions is a current topic of discussion among hydrologists and water managers in the region, but no comparative study has been performed to analyze the effects of different recharge distributions on groundwater simulations. This study investigates the importance of the distribution of aquifer recharge in simulating regional groundwater flow in basin‐fill aquifers by calibrating a groundwater‐flow model to four different recharge distributions, all with the same total amount of recharge. Similarities are seen in results from steady‐state models for optimized hydraulic conductivity values, fit of simulated to observed hydraulic heads, and composite scaled sensitivities of conductivity parameter zones. Transient simulations with hypothetical storage properties and pumping rates produce similar capture rates and storage change results, but differences are noted in the rate of drawdown at some well locations owing to the differences in optimized hydraulic conductivity. Depending on whether the purpose of the groundwater model is to simulate changes in groundwater levels or changes in storage and capture, the distribution of aquifer recharge may or may not be of primary importance.  相似文献   

12.
Spreading‐basin methods have resulted in more than 130 million cubic metres of recharge to the unconfined Navajo Sandstone of southern Utah in the past decade, but infiltration rates have slowed in recent years because of reduced hydraulic gradients and (or) clogging. Trench infiltration is a promising alternative technique for increasing recharge and minimizing evaporation. This paper uses a variably saturated flow model to further investigate the relative importance of the following variables on rates of trench infiltration to unconfined aquifers: saturated hydraulic conductivity, trench spacing and dimensions, initial water‐table depth, alternate wet/dry periods, and number of parallel trenches. Modelling results showed (1) increased infiltration with higher hydraulic conductivity, deeper initial water tables, and larger spacing between parallel trenches, (2) deeper or wider trenches do not substantially increase infiltration, (3) alternating wet/dry periods result in less overall infiltration than keeping the trenches continuously full, and (4) larger numbers of parallel trenches within a fixed area increases infiltration but with a diminishing effect as trench spacing becomes tighter. An empirical equation for estimating expected trench infiltration rates as a function of hydraulic conductivity and initial water‐table depth was derived and can be used for evaluating feasibility of trench infiltration in other hydrogeologic settings. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

13.
This study addresses the influence of landslide dams on surface water drainage and groundwater flow. In the study area of Scanno Lake and Sagittario River (Central Italy), a limestone rockslide‐avalanche formed a lake, which has an outlet that is occasionally active, showing infiltration into the rockslide dam. Several springs are present at the lake's base and are partly fed by seepage through the rockslide debris. Piezometric surveys, discharge measurements, pumping tests and chemical analyses are tools used to build a conceptual model of the groundwater flow and to evaluate the flow through the rockslide debris. Seasonal water isotopic signatures validate the assumed model, showing a mixing of infiltration recharge and groundwater seepage throughout the rockslide debris. Various recharge areas have been found for springs, pointing out those directly fed by the rockslide debris aquifer. Hypotheses about seasonal groundwater mixing between the regional carbonate aquifer and the rockslide debris aquifer are supported by isotope results. Seasonal changes in groundwater table level due to recharge and surface losses from seasonal outlet have been correlated with isotopic groundwater composition from the rockslide debris aquifer and the downstream springs; this relationship highlights the role of the rockslide dam body on the hydrodynamics of the studied area. Relationships between surface waters and groundwater in the area have been completely understood on the basis of water isotopic fingerprinting, finally obtaining a complete evaluation of groundwater renewable resources and its regimen. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

14.
This study investigates spatial patterns and temporal dynamics of aquifer–river exchange flow at a reach of the River Leith, UK. Observations of sub‐channel vertical hydraulic gradients at the field site indicate the dominance of groundwater up‐welling into the river and the absence of groundwater recharge from surface water. However, observed hydraulic heads do not provide information on potential surface water infiltration into the top 0–15 cm of the streambed as these depths are not covered by the existing experimental infrastructure. In order to evaluate whether surface water infiltration is likely to occur outside the ‘window of detection’, i.e. the shallow streambed, a numerical groundwater model is used to simulate hydrological exchanges between the aquifer and the river. Transient simulations of the successfully validated model (Nash and Sutcliff efficiency of 0·91) suggest that surface water infiltration is marginal and that the possibility of significant volumes of surface water infiltrating into non‐monitored shallow streambed sediments can be excluded for the simulation period. Furthermore, the simulation results show that with increasing head differences between river and aquifer towards the end of the simulation period, the impact of streambed topography and hydraulic conductivity on spatial patterns of exchange flow rates decreases. A set of peak flow scenarios with altered groundwater‐surface water head gradients is simulated in order to quantify the potential for surface water infiltration during characteristic winter flow conditions following the observation period. The results indicate that, particularly at the beginning of peak flow conditions, head gradients are likely to cause substantial increase in surface water infiltration into the streambed. The study highlights the potential for the improvement of process understanding of hyporheic exchange flow patterns at the stream reach scale by simulating aquifer‐river exchange fluxes with a standard numerical groundwater model and a simple but robust model structure and parameterization. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

15.
Transmission losses from the beds of ephemeral streams are thought to be a widespread mechanism of groundwater recharge in arid and semi-arid regions and support a range of dryland hydro-ecology. Dryland areas cover ~40% of the Earth's land surface and groundwater resources are often the main source of freshwater. It is commonly assumed that where an unsaturated zone exists beneath a stream, the interaction between surface water and groundwater is unidirectional and that groundwater does not exert a significant feedback on transmission losses. To test this assumption, we conducted a series of numerical model experiments using idealised two-dimensional channel-transects to assess the sensitivity and degree of interaction between surface and groundwater for typical dryland ephemeral stream geometries, hydraulic properties and flow regimes. We broaden the use of the term ‘stream–aquifer interactions’ to refer not just to fluxes and water exchange but also to include the ways in which the stream and aquifer have a hydraulic effect on one another. Our results indicate that deep water tables, less frequent streamflow events and/or highly permeable sediments tend to result in limited bi-directional hydraulic interaction between the stream and the underlying groundwater which, in turn, results in high amounts of infiltration. With shallower initial depth to the water table, higher streamflow frequency and/or lower bed permeability, greater ‘negative’ hydraulic feedback from the groundwater occurs which in turn results in lower amounts of infiltration. Streambed losses eventually reach a constant rate as initial water table depths increase, but only at depths of 10s of metres in some of the cases studied. Our results highlight that bi-directional stream–aquifer hydraulic interactions in ephemeral streams may be more widespread than is commonly assumed. We conclude that groundwater and surface water should be considered as connected systems for water resource management unless there is clear evidence to the contrary.  相似文献   

16.
Farmed catchments in the Mediterranean area often exhibit dense networks of ditches which are also preferential zones of water table recharge, and thereby of groundwater contamination. This study presents an experimental analysis of seepage losses and related groundwater recharge patterns during a typical Mediterranean runoff event at the scale of a ditch located above a shallow water table. The objectives were (i) to evaluate the patterns of water table recharge by seepage in a ditch, (ii) to study the main flow processes occurring during recharge, and (iii) to estimate solute propagation in case of contaminated flow in the ditch. The field observation indicated three major points. Firstly, they showed that seepage losses during a runoff event in a ditch can rapidly lead to a significant recharge of a shallow water table. Secondly, the recharge induces a groundwater mound much larger than the event plume. The infiltrated water and the accompanying solutes remained in the vicinity of the ditch. The patterns of groundwater recharge and contamination appeared very different. Lastly, both unsaturated and saturated‐piston flow processes were observed which suggests that a variably‐saturated flow modelling approach ought to be used to simulate the ditch‐water shallow table interaction. Finally, the study indicates that the patterns of water table recharge and contamination in Mediterranean catchments with dense ditches network vary largely in space and time, and will require dense monitoring networks to estimate the evolution of the average contamination levels. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

17.
Analysis of water movement in paddy rice fields (I) experimental studies   总被引：2，自引：0，他引：2  
For the purpose of increasing the amount of ground water recharge, we investigated the hydraulic characteristics of water infiltration in a flooded paddy rice field in Ten-Chung, Chung-Hwa county, Taiwan. Experimental results based on mini-tensiometers and double ring infiltrometer measurements indicated that the least permeable layer occurred at the interface of the puddled topsoil and non-puddled subsoil. The average thickness of this layer was about 7.5 cm and saturated hydraulic conductivity ranged from 0.034 to 0.083 cm/day. Vertical infiltration flow was saturated within the plow sole layer and became unsaturated in the subsoil below the plow sole layer. The hydraulic conductivity of the subsoil, 20–30 times greater than that of the plow sole layer, revealed that the subsoil was more permeable than the plow sole layer. In situ measurements also demonstrated that breakage of the plow sole layer increased infiltration rate by a factor of 3.7. Increasing ponded water depth from 6 to 16 cm increased infiltration 1.5 fold. It is suggested that using the fallow paddy rice fields without puddling is a feasible way to enhance groundwater recharge, but for cultivated paddy rice fields, breaking the plow sole needs further study in terms of its recoverability and because of the potential contamination of the shallow aquifer by agrochemicals. The experimental data can be applied in numerical simulation models to quantify detailed water movement mechanisms and accurately estimate the amount of ground water recharge in paddy rice fields.  相似文献   

18.
Sea water intrusion and remediation in the Upper Floridan Aquifer in South Carolina is simulated using the finite-element model SUTRA developed by the U.S. Geological Survey. A sensitivity analysis of the effect of the hydrogeologic parameters on the sea water recharge and seepage velocities is performed. An increase in confining unit and/or in aquifer conductivity results in an increase of the sea water recharge. An increase in aquifer porosity results in a decrease of the sea water recharge. Among the three remedial techniques simulated—reduced aquifer withdrawals, an injection well, and a combined injection and capture well—the reduced aquifer withdrawals and injection well are the best methods for preventing sea water intrusion.  相似文献   

19.
Groundwater-flow models depend on hydraulic head and flux observations for evaluation and calibration. A different type of observation—change in storage measured using repeat microgravity—can also be used for parameter estimation by simulating the expected change in gravity from a groundwater model and including the observation misfit in the objective function. The method is demonstrated using new software linked to MODFLOW input and output files and field data from the vicinity of the All American Canal in southeast California, USA. Over a 10-year period following lining of the previously highly permeable canal with concrete, gravity decreased by over 100 μGal (equivalent to about 2.5 m of free-standing water) at some locations as seepage decreased and the remnant groundwater mound dissipated into the aquifer or was removed by groundwater pumping. Simulated gravity from a MODFLOW model closely matched observations, and repeat microgravity data proved useful for constraining both hydraulic conductivity and specific yield estimates. Specific yield estimated using the infinite-horizontal slab approximation agreed well with model-derived values, and the departure from the linear, flat-water-table approximation was small, less than 2%, despite relatively large and dynamic water-table slope. First-order second-moment parameter uncertainty analysis shows reduction in uncertainty for all hydraulic conductivity and specific yield parameter estimates with the addition of repeat microgravity data, as compared to drawdown data alone.  相似文献   

20.
Applicability of spectral analysis to determine hydraulic diffusivity   总被引：1，自引：1，他引：0  
This study is to evaluate the applicability of estimating the one-dimensional horizontal hydraulic diffusivity of an unconfined aquifer with time-dependent fluctuation of lateral head and vertical recharge boundaries using observed water level spectra. Different models of boundary condition are imposed to evaluate the statistical significance between the calculated hydraulic diffusivity (ξ′) with the given hydraulic diffusivity (ξ). The auto-spectra of the water level in observation wells tapping the same aquifer are closely related to those at the disturbed boundaries. For an aquifer with a constant hydraulic diffusivity, the water level fluctuation in the monitoring wells is linearly related to the water level spectra observed at the boundaries. The spectral density function of aquifer hydraulic head varies inversely with specific yield (S y) and directly with recharge. Given small variation in water level spectra at the disturbed boundaries, the water level fluctuation in the aquifer is affected by the recharge condition and the aquifer spectral density function is sensitive to S y. Using an iterative technique to estimate ξ from 1400 sets of given parameters, 99% of the ξ′/ξ values deviated within only one order of magnitude with the model length (L) being equal to 1 km and 10 km. For L equal to 100 m, approximately 82% of the ξ′/ξ population falls within two orders of magnitude. Therefore, spectral analysis of aquifer hydraulic head response can be used to estimate the hydraulic diffusivity of an unconfined aquifer which is affected by periodic variations in recharge and head at boundaries.  相似文献   

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