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1.
In this study, two conceptual models, the classic reservoir (CR) model and exchange reservoirs model embedded by dual porosity approach (DPR) are developed for simulation of karst aquifer functioning drained by multiple outlets. The performances of two developed models are demonstrated at a less developed karstic aquifer with three spring outlets located in Zagros Mountain in the south‐west of Iran using 22‐years of daily data. During the surface recharge, a production function based on water mass balance is implemented for computing the time series of surface recharge to the karst formations. The efficiency of both models has been assessed for simulation of daily spring discharge during the recession and also surface recharge periods. Results indicate that both CR and DPR models are capable of simulating the ordinates of spring hydrographs which drainage less developed karstic aquifer. However, the goodness of fit criteria indicates outperformance of DPR model for simulation of total hydrograph ordinates. In addition, the DPR model is capable of quantifying hydraulic properties of two hydrologically connected overlapping continua conduits network and fissure matrix which lays important foundations for the mining operation and water resource management whereas homogeneous model representations of the karstic subsurface (e.g., the CR) do not work accurately in the karstic environment.  相似文献   

2.
Delineation of regional arid karstic aquifers: an integrative data approach   总被引：1，自引：0，他引：1  
This research integrates data procedures for the delineation of regional ground water flow systems in arid karstic basins with sparse hydrogeologic data using surface topography data, geologic mapping, permeability data, chloride concentrations of ground water and precipitation, and measured discharge data. This integrative data analysis framework can be applied to evaluate arid karstic aquifer systems globally. The accurate delineation of ground water recharge areas in developing aquifer systems with sparse hydrogeologic data is essential for their effective long-term development and management. We illustrate the use of this approach in the Cuatrociénegas Basin (CCB) of Mexico. Aquifers are characterized using geographic information systems for ground water catchment delineation, an analytical model for interbasin flow evaluation, a chloride balance approach for recharge estimation, and a water budget for mapping contributing catchments over a large region. The test study area includes the CCB of Coahuila, Mexico, a UNESCO World Biosphere Reserve containing more than 500 springs that support ground water-dependent ecosystems with more than 70 endemic organisms and irrigated agriculture. We define recharge areas that contribute local and regional ground water discharge to springs and the regional flow system. Results show that the regional aquifer system follows a topographic gradient that during past pluvial periods may have linked the Río Nazas and the Río Aguanaval of the Sierra Madre Occidental to the Río Grande via the CCB and other large, currently dry, upgradient lakes.  相似文献   

3.
Weiss M  Gvirtzman H 《Ground water》2007,45(6):761-773
The fraction of rain that is annually recharged to ground water is a function of the transient quantities of precipitation (wet vs. dry years) as well as other meteorological and geologic factors, and thus it is very difficult to estimate. In this study, we have used long records (20 to 30 years) of precipitation and spring discharge to reconstruct the transient character of yearly recharge. These data sets were used to calibrate numerical ground water flow models on the less than 3 km(2) scale for four separate perched karstic aquifers in the Judean and Samarian Mountains of Israel. The stratification and karstic character of the local carbonate rock aquifers cause ground water to flow through discrete dissolution channels and to discharge at isolated springs. An innovative, dual-porosity approach was used where a finite-difference solution simulates flow in the rock matrix, while the karstic channels are simulated using computationally simple drains. Perched conditions are also simulated innovatively using MODFLOW by treating the bottom unsaturated layer as if it is saturated, but by assuming zero pressure head throughout the "unsaturated" layer. Best fitting between measured and computed spring hydrograph data has allowed us to develop a set of empirical functions relating measured precipitation to recharge to the aquifer. The generic methodology presented gives insight into the suspected changes in aquifer recharge rates between particularly wet or dry years.  相似文献   

4.
Coastal fresh water aquifers are an increasingly desirable resource. In a karstic aquifer, sea water intrusion occurs as a salt water wedge, like in porous media. However, preferential flow conduits may alter the spatial and temporal distribution of the salt water. This is typically the case when the outlet of the aquifer is a brackish spring. This paper shows that salinity and flow rate variations at a spring, where salinity is inversely proportional to discharge, can help to understand the hydrodynamic functioning of the aquifer and to locate the fresh water-sea water mixing zone deep inside the aquifer. The volume of water-filled conduit between the sea water intrusion zone and the spring outlet is calculated by the integral over time of the flow rate during the time lag between the flow rate increase and the salinity decrease as measured at the spring. In the example of the spring at Almyros of Heraklio (Crete, Greece), this time lag is variable, depending on the discharge, but the volume of water-filled conduit appears to be constant, which shows that the processes of salt water intrusion and mixing in the conduit are constant throughout the year. The distance between the spring and the zone where sea water enters the conduit is estimated and provides an indication of the position where only fresh water is present in the conduit.  相似文献   

5.
A procedure to simulate karstic aquifers is presented. It is based on a simulation of spring discharge using precipitation and, where necessary, temperature as input data. The karstic aquifer system is considered to be divided into three zones: the surface zone, the unsaturated zone (UZ) and the saturated zone (SZ). Each of these is described by a transfer function that determines the water supplied from the overlying zone. Water loss through evapotranspiration is calculated empirically and subtracted from the total precipitation in order to obtain the effective infiltration into the UZ. The transfer function characterizing the UZ can be expressed as a convolution function. The UZ acts as a buffer, delaying effective infiltration into the SZ. Water discharge from the SZ is described by the recession function of the spring, and this becomes the transfer function that characterizes the emergence of water from the SZ. The model permits the simulation of the influence of pumped abstractions from the system by a simple modification of the transfer functions involved. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

6.
Karstic formations function as three-dimensional (3D) hydrological basins, with both surface and subsurface flows through fissures, natural conduits, underground streams and reservoirs. The main characteristic of karstic formations is their significant 3D physical heterogeneity at all scales, from fine fissuration to large holes and conduits. This leads to dynamic and temporal variability, e.g. highly variable flow rates, due to several concurrent flow regimes with several distinct response times. The temporal hydrologic response of karstic basins is studied here from an input/output, systems analysis viewpoint. The hydraulic behaviour of the basins is approached via the relationship between hydrometeorological inputs and outputs. These processes are represented and modeled as random, self-correlated and cross-correlated, stationary time processes. More precisely, for each site-specific case presented here, the input process is the total rainfall on the basin and the output process is the discharge rate at the outlet of the basin (karstic spring). In the absence of other data, these time processes embody all the available information concerning a given karstic basin. In this paper, we first present a brief discussion of the physical structure of karstic systems. Then, we formulate linear and nonlinear models, i.e. functional relations between rainfall and runoff, and methods for identifying the kernel and coefficients of the functionals (deterministic vs. statistical; error minimisation vs. polynomial projection). These are based mostly on Volterra first order (linear) or second order (nonlinear) convolution. In addition, a new nonlinear threshold model is developed, based on the frequency distribution of interannual mean daily runoff. Finally, the different models and identification methods are applied to two karstic watersheds in the french Pyrénées mountains, using long sequences of rainfall and spring outflow data at two different sampling rates (daily and semi-hourly). The accuracy of nonlinear and linear rainfall-runoff models is tested at three time scales: long interannual scale (20 years of daily data), medium or seasonal scale (3 months of semi-hourly data), and short scale or “flood scale” (2 days of semi-hourly data). The model predictions are analysed in terms of global statistical accuracy and in terms of accuracy with respect to high flow events (floods).  相似文献   

7.
Neural network simulation of spring flow in karst environments   总被引：2，自引：2，他引：0  
Daily discharges of two springs lying in a karstic environment were simulated for a period of 2.5 years with the use of a multi-layer perceptron back-propagation neural network. Two models were developed for the springs, one relying on the original data and another where the missing discharge values were supplemented by assuming linear relationships during base flow conditions. For both springs the mean square error of the two models did not differ significantly, with an improvement exhibited at the extremes, during the network’s training phase, by the model that utilized the extended data set, the results of which are reported here. The time lag between precipitation and spring discharge differed significantly for the two springs indicating that in karstic environments hydraulic behavior is dominated, even within a few hundred meters, by local conditions. Optimum training results were attained with a Levenberg–Marquardt algorithm resulting in a network architecture consisting of two input layer neurons, four hidden layer neurons, and one output layer neuron, the spring’s discharge. The neural network’s predictions captured the behavior for both springs and followed very closely the discontinuities in the discharge time series. Under-/over-estimation of observed discharges for the two springs remained below 3 %, with the exception of a few local maxima where the predicted discharges diverged more strongly from observed values. Inclusion of temperature data did not add to the improvement of predictions. Finally, optimum predictions were attained when past discharge data were added to the input record and discharge differentials rather than direct discharges were calculated resulting in elimination of any local maximum discrepancy between observed and predicted discharge values.  相似文献   

8.
The field hydrology model DRAINMOD integrated with Arc Hydro in geographical information system (GIS) framework (Arc Hydro–DRAINMOD) was used to simulate the hydrological response of a coastal watershed in southeast Sweden. Arc Hydro–DRAINMOD uses a distributed approach to route water from each field edge to the watershed outlet. In the framework the Arc Hydro data model was used to describe the stream network in the watershed and to connect the individual simulated DRAINMOD‐field outflow time series from each plot using Arc Hydro schema‐links features, which were summed at Arc Hydro schema‐nodes features along the stream network to generate the stream network flow. Hydrology data collected during six periods between 2003 and 2008 were used to test Arc Hydro–DRAINMOD and its performance was evaluated by considering uncertainties in model inputs using generalized likelihood uncertainty estimation (GLUE). The GLUE estimates obtained (uncertainty bands 5% and 95%) agreed satisfactorily with measured monthly discharges. The percentage of time in which the observed discharges were bracketed by the uncertainty bands was 88% in calibration periods and 75% in validation periods. Although monthly time step simulations showed good agreement with observed discharges during the two main discharge events in spring, the contradictory daily time step results indicate that the watershed response simulations on a daily basis need to be improved. The uncertainty analysis showed that in periods of higher discharge, such as spring periods, the uncertainty in prediction was higher. It is important to note that these uncertainty estimations using the GLUE procedure include the uncertainties in measured discharge values, model inputs, boundary conditions and model structures. It was estimated that stream baseflow represented 42% of the total watershed discharge, but further research is needed to confirm this. These results show that the new Arc Hydro–DRAINMOD framework is applicable for predicting discharge from artificially drained watersheds in southeast Sweden. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

9.
Karst spring responses examined by process-based modeling   总被引：8，自引：0，他引：8  
Birk S  Liedl R  Sauter M 《Ground water》2006,44(6):832-836
Ground water in karst terrains is highly vulnerable to contamination due to the rapid transport of contaminants through the highly conductive conduit system. For contamination risk assessment purposes, information about hydraulic and geometric characteristics of the conduits and their hydraulic interaction with the fissured porous rock is an important prerequisite. The relationship between aquifer characteristics and short-term responses to recharge events of both spring discharge and physicochemical parameters of the discharged water was examined using a process-based flow and transport model. In the respective software, a pipe-network model, representing fast conduit flow, is coupled to MODFLOW, which simulates flow in the fissured porous rock. This hybrid flow model was extended to include modules simulating heat and reactive solute transport in conduits. The application of this modeling tool demonstrates that variations of physicochemical parameters, such as solute concentration and water temperature, depend to a large extent on the intensity and duration of recharge events and provide information about the structure and geometry of the conduit system as well as about the interaction between conduits and fissured porous rock. Moreover, the responses of solute concentration and temperature of spring discharge appear to reflect different processes, thus complementing each other in the aquifer characterization.  相似文献   

10.
Karstic watersheds are highly complex hydrogeological systems that are characterized by a multiscale behaviour corresponding to the different pathways of water in these systems. The main issue of karstic spring discharge fluctuations consists in the presence and the identification of characteristic time scales in the discharge time series. To identify and characterize these dynamics, we acquired, for many years at the outlet of two karstic watersheds in South of France, discharge data at 3‐mn, 30‐mn and daily sampling rate. These hydrological records constitute to our knowledge the longest uninterrupted discharge time series available at these sampling rates. The analysis of the hydrological records at different levels of detail leads to a natural scale analysis of these time series in a multifractal framework. From a universal class of multifractal models based on cascade multiplicative processes, the time series first highlights two cut‐off scales around 1 and 16 h that correspond to distinct responses of the aquifer drainage system. Then we provide estimates of the multifractal parameters α and C1 and the moment of divergence qD corresponding to the behaviour of karstic systems. These results constitute the first estimates of the multifractal characteristics of karstic spingflows based on 10 years of high‐resolution discharge time series and should lead to several improvements in rainfall‐karstic springflow simulation models. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

11.
Understanding rainfall‐runoff processes is crucial for prevention and prediction of water‐related natural disasters. Sulfur hexafluoride (SF6) is a potential tracer, but few researches have applied it for rainfall‐runoff process studies. We observed multiple tracers including SF6 in spring water at 1‐ to 2‐hr intervals during rainstorm events to investigate the effectivity of SF6 tracer in rainfall–runoff studies through the clarification of rainfall–runoff process. The target spring is a perennial spring in a forested headwater catchment with an area of 0.045 km2 in Fukushima, Japan. The relationship between the SF6 concentration in spring water and the spring discharge volume was negative trend; the SF6 concentration in spring water becomes low as the spring discharge volume increases especially during rainstorms. The hydrograph separation using SF6 and chloride ion tracers was applied for determining the contribution of principal sources on rainfall–runoff water. It suggested more than 60% contribution of bedrock groundwater at the rainfall peak and high percentage contribution continued even in the hydrograph recession phase. Based on observed low SF6 concentration in groundwater after heavy rainfall, the replacement of groundwater near the spring with bedrock groundwater is indicated as a mechanism for water discharge with low SF6 concentration during rainfall events. Consequently, rainstorm events play an important role as triggers in discharging water stored in the deeper subsurface area. In addition, SF6 tracer is concluded as one of the strongest tracers for examining rainfall–runoff process studies. And, therefore, this study provided new insights into the dynamics of groundwater and its responses to rainfall in terms of SF6 concentration variance in water in headwater regions.  相似文献   

12.
Wicks C  Kelley C  Peterson E 《Ground water》2004,42(3):384-389
Adverse impacts on the health of some fish populations, such as skewed sex distributions, have been noted in surface waters and in laboratory experiments with relatively low concentrations (above 25 ng/L) of natural estrogen (17 beta-estradiol--E2). Sources of E2 to surface and ground waters can include avian, human, and mammalian waste products. The Ozark Plateau Aquifer (OPA) is a karstic basin that receives a significant portion of its water through losing reaches of rivers. Thus, there is a direct connection between surface water and ground water. The OPA was targeted for an E2 study to assess the potential for adverse health effects to aquatic organisms living in the system. Eight springs, which drain the aquifer, were sampled quarterly. The concentrations of E2 in the OPA ranged from 13 to 80 ng/L. For any one sampling event, the concentrations of E2 at the spring waters were statistically similar; however, the concentrations of E2 at all springs varied throughout the year. At Maramec Spring, one of the larger springs, the E2 concentration, was correlated with discharge. Based on the correlation between discharge and E2 concentration, aquatic organisms living in the plateau or in its discharged waters, including the threatened southern cavefish T. subterraneus, are exposed to concentration of E2 above 25 ng/L approximately 60% of the time. This implies that organisms living in karst basins throughout the OPA are likely exposed to E2 concentrations that may adversely impact their reproductive success for a significant portion of each year.  相似文献   

13.
Chemical and isotopic analysis of karst water dripping over a one year period from seeps in a cave above the Cenomanian aquifer in the Judea hills of Israel lead to several conclusions: (i) The tritium ages and the chemical composition of water from different seeps in a karstic cave vary greatly, (ii) The reservoirs in the upper part of the vadose zone hold water for up to several decades, (iii) Some of the cave seeps are mixtures of the old and more recent meteoric water from paths of different length, (iv) The history of storm events can only be traced in some of the seeps, (v) For most dripping seeps there is no immediate response of seepage discharge to the rainfall intensity and quantity—i.e. the seepage discharge is fairly constant.  相似文献   

14.
In-depth studies of water and sediment fluxes from rivers into the sea are very important for understanding the interactions between land and sea. This paper is concerned with identifying the changes in the time series of water and sediment fluxes from Feiyun River in Zhejiang Province, China. Inter- and intraannual variability in the water discharge and sediment load of the Feiyun River into the sea are analyzed using the observed data of runoff (1956–2008) and sediment (1957–2008) at Xuekou Station, which is in the main channel. The results show that there is a good peak–valley correlation between the water discharge and sediment load, and there are obvious seasonal variations, with a 65.7% water discharge and 89.2% sediment load during the flooding periods. Water discharge is mainly controlled by natural rainfall, but the construction of the upstream reservoirs in 1997 increased the discharge amount in the dry season and decreased the amount in the flooding season. Sediment loads were reduced after a huge flood in 1990 and construction of upstream reservoirs, while the latter also decreased the sediment load during the typhoon flooding period. Furthermore, the correlation between water discharge and sediment load is also affected by the flood and reservoir construction. There are some differences in the regression equations of sediment load and water discharge for 1957–1989, 1991–1996, and 1997–2008.  相似文献   

15.
Based on the groundwater development process, and regional economic and social developing history, we divided the spring hydrological process of the Liulin Springs Basin into two periods: pre‐1973 and post‐1974. In the first period (i.e. 1957–1973), the spring discharge was affected by climate variation alone, and in the second period (i.e. 1974–2009), the spring discharge charge was influenced by both climate variation and human activities. A piecewise analysis strategy was used to differentiate the contribution of anthropogenic activities from climate variation on karst spring discharge depletion in the second period. Then, the ARIMAX model was applied to spring flow time series of the first period to develop a model for the effects of climate variation only. Using this model, we estimated the spring discharge in the second period solely under the influence of climate variation. Based on the water budget, we subtracted observed spring discharge from the estimated spring discharge and acquired the contribution of human activities on spring discharge depletion for the second period. The results of the analysis indicated that the contribution of climate variation to the spring discharge depletion is?0.20 m3/s from 1970s to 2000s. The contribution of anthropogenic activities to the spring flow depletion was ?2.56 m3/s in 2000s, which was about 13 times more than that of climate variation. Our analysis further indicates that groundwater exploitation only accounts for 29% of the spring flow depletion due to the effects of human activities. The remaining 71% of the depletion is likely to be caused by other human activities, including dam building, dewatering during coal mining, and deforestation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

16.
Seth Rose 《水文研究》1994,8(5):481-496
Major-ion variability related to discharge was analysed in a forested 187 km2 mafic Piedmont Province watershed using statistical (both parametric and non-parametric), graphical (box-plots) and curve-fitting (log concentration-log discharge) techniques. Baseflow alkalinity and base cation concentrations show systematic temporal variations as a result of the influx of additional water that occurs during the late autumn to early spring. Regression analyses indicate that storm-related discharge and baseflow generated during periods of water surplus are characterized by similar dilution slopes. Mass balance estimates indicate that the additional water, which comprises storm/recession discharge and base-flow from late autumn to early spring, is between about 30 and 80% as concentrated as summer low-flow. The thick clay-rich soil mantle represents a key control on solute concentrations in that it stores water for periods of time sufficient for a high degree of water-mineral interaction to occur. Hence solute-discharge relationships (C = aQb, where b is typically < 0) are characterized by relatively low slope values and there is ample acid neutralizing capacity throughout the range of discharge. Owing to the predominance of amphibolite, solute efflux related to rock weathering from the Falling Creek watershed is much greater than other more felsic locations within the region. Statistical analyses (Mest and the non-parametric Mann-Whitney-Wilcoxon test), along with accompanying box-plot representations, provide a useful method of describing systematic annual hydrochemical variation within streamflow. These methods are particularly effective for those instances in which a long-term data set exists, but is limited to relatively few sampling periods per year.  相似文献   

17.
ABSTRACT

Crete is a Mediterranean, karst-dominated island, characterized by long drought periods. The Karst-SWAT model, combined with 11 climate change scenarios, was run to assess climate change impacts on the island under two set-ups, both using the auto-irrigation function of the model: (1) with water drawn from the shallow or deep aquifer, and (2) with irrigated water derived from an unlimited outside source. The first set-up provided insight into the fluctuation of future irrigation needs, and when compared to the second set-up, enabled quantification of the future water deficit. The Water Exploitation Index was used to describe the spatial variability of future water stress on Crete. A decrease in both surface and karstic spring flows is foreseen, especially after 2060 (24.2 and 16.5%, respectively). Simulated irrigation water demand and water deficit show continuous increase throughout the projection period (2020–2098).  相似文献   

18.
This study focuses on the coupled transport of dissolved constituents and particulates, from their infiltration on a karst plateau to their discharge from a karst spring and their arrival at a well in an alluvial plain. Particulate markers were identified and the transport of solids was characterised in situ in porous and karstic media, based on particle size analyses, SEM, and traces. Transport from the sinkhole to the spring appeared to be dominated by flow through karst: particulate transport was apparently conservative between the two sites, and there was little difference in the overall character of the particle size distribution of the particulates infiltrating the sinkhole and of those discharging from the spring. Qualitatively, the mineralogy of the infiltrating and discharging material was similar, although at the spring an autochthonous contribution from the aquifer was noted (chalk particles eroded from the parent rock by weathering). In contrast, transport between the spring and the well appears to be affected by the overlying alluvium: particles in the water from the well, showed evidence of considerable size-sorting. Additionally, SEM images of the well samples showed the presence of particles originating from the overlying alluvial system; these particles were not found in samples from the sinkhole or the spring. The differences between the particulates discharging from the spring and the well indicate that the water pumped from the alluvial plain is coming from the karst aquifer via the very transmissive, complex geologic interface between the underlying chalk formation and the gravel at the base of the overlying alluvial system.  相似文献   

19.
ABSTRACT

Karst aquifers and springs are important with respect to their potential for supplying drinking water in regions suffering from water scarcity in Iran. Accordingly, it is essential to determine the recharge potential of the catchment and the regions with higher obtainability potential. This study provides a road map for the Sheshpeer catchment in southern Iran. A recharge potential (RP) map was produced from which a recharge index (RI) was computed for several selected springs in the catchment. Furthermore, the unit discharge (q) – defined as the average annual discharge for a given catchment area and unit rainfall depth for each spring – was calculated. The plot of q versus RI for the springs showed a linear positive relationship between the two variables (R 2 = 0.9). Applying the trend equation of this plot to the whole Sheshpeer karstic catchment reveals that its long-term recharge coefficient is 0.74.  相似文献   

20.
This study addresses the spatial variations in water quality along the River Vène (France). The Vène drains a 67 km2 rural basin, with a large karstic area, located in a Mediterranean context. A 1 day sampling campaign was conducted along the river, in winter low‐flow conditions (February 2003). Physico‐chemical parameters and water flow discharge were measured in situ during the sampling campaign. Water quality was evaluated by determining the concentrations of nitrogen and phosphorus in water and bed‐sediment samples. Nitrogen and phosphorus loads were evaluated taking into account the measured concentrations and discharge. The campaign included 18 sampling points and concerned the whole river from the spring to the outlet, plus the main inputs, i.e. sewage treatment works, main tributaries and karstic springs. The spatial evolution of nitrogen and phosphorus loads along the river allowed the significant role of point‐source inputs to be demonstrated. The decrease in nutrient loads along the river occurred mainly in specific reaches where fine sediments had accumulated. In these zones, phosphorus is trapped in the bed sediments in calcium‐bound phosphates due to precipitation processes. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

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