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1.
Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especially during winter seasons when extremely variable rainfall of high intensities prevails. An additional challenge is posed when managed recharge of storm water is applied, since karst aquifers display a high spatial variability of hydraulic properties. In these cases, adapted protection concepts are required to address the interaction of surface water and groundwater. In this study a combined protection approach for the surface catchment of the managed aquifer recharge site at the Wala reservoir in Jordan and the downstream Hidan wellfield, which are both subject to frequent bacteriological contamination, is developed. The variability of groundwater quality was evaluated by correlating contamination events to rainfall, and to recharge from the reservoir. Both trigger increased wadi flow downstream of the reservoir by surface runoff generation and groundwater seepage, respectively. A tracer test verified the major pathway of the surface flow into the underground by infiltrating from pools along Wadi Wala. An intrinsic karst vulnerability and risk map was adapted to the regional characteristics and developed to account for the catchment separation by the Wala Dam and the interaction of surface water and groundwater. Implementation of the proposed protection zones for the wellfield and the reservoir is highly recommended, since the results suggest an extreme contamination risk resulting from livestock farming, arable agriculture and human occupation along the wadi. The applied methods can be transferred to other managed aquifer recharge sites in similar karstic environments of semi-arid regions.  相似文献   

2.
Groundwater recharge rates calculated with the GROWA model have been applied as the recharge boundary condition for the regional groundwater model Rurscholle. This model simulates groundwater dynamics in the Pleistocene aquifers of the Lower Rhine lignite mining area (Germany). GROWA uses an area-differentiated approach to calculate recharge rates depending on runoff-relevant site characteristics, which are represented by a set of baseflow indices. The regional accuracy of the coupled groundwater and GROWA models has been checked using groundwater hydrographs as validation criteria. The results suggest that the current (unadjusted) version of GROWA underestimates the regional groundwater recharge rate by 10–20 mm/yr. The comparative analysis identified areas where recharge calculations could be improved by adjusting the baseflow indices for areas where runoff is dominated by slope, low water-logging and a low degree of sealing. Using the adjusted set of baseflow indices, the mean groundwater recharge rate of the Rurscholle region was modelled as approx. 170 mm/yr. This study highlights the benefit of using a coupled approach and being able to independently calibrate and validate groundwater recharge boundary conditions in regional groundwater models.  相似文献   

3.
In a stream–aquifer system, adequate knowledge of the aquifer hydraulic parameters is paramount for the analysis of groundwater/surface-water interaction. In such systems, analytical flood-wave response models are commonly used to assess these parameters. However, when an important means of direct recharge (precipitation) occurs simultaneously with the stream flood waves, the classical flood-wave response model (i.e. when only stream flood waves are considered as an input signal) leads to overestimated and variable values of the aquifer hydraulic parameters. In this study, an analytical flood-wave response model was implemented to determine hydraulic parameters of the Merguellil alluvial aquifer (central Tunisia) taking into account the recharge rate as a second input signal. An array of three piezometers and a river-stage gauge equipped with an automated Diver data logger were installed in the floodplain of the Merguellil Wadi. The results showed a good agreement between the observed and modelled hydrographs when the recharge rate was considered, which allows the model to provide the same value of diffusivity (50–70 m2 h?1) in the three piezometers and for all flood events being tested. However, when the recharge rate was not taken into account, the model gave an overestimated diffusivity with a very poor hydrograph match. Overall, the methodology described in this paper can be applicable to any area in the world because of its simplicity and its better estimation of aquifer hydraulic parameters.  相似文献   

4.
The Kucuk Menderes River Basin in western Turkey has been facing continuous groundwater-level decline for decades. Previous studies have suggested that, to avoid aquifer depletion in the basin, artificial recharge structures should be constructed. To assess artificial aquifer recharge potential in one of the subbasins, a two-dimensional (2-D) groundwater model was set up using SEEP/W software. The material functions and parameters used in the model for both saturated and unsaturated conditions were taken from previous studies. The model has been calibrated under transient conditions. The excess runoff volume that could be collected in the recharge basins was estimated from flood frequency analysis. Various scenarios were simulated to observe the change in groundwater level and storage with respect to different exceedance probabilities. Simulation results suggest that a significant increase in groundwater storage is achieved by applying surface artificial-recharge methods. In addition to the recharge basins, to reinforce the effect of artificial recharge, simulations are repeated with underground dam construction at the downstream side of the basin. Although groundwater storage is increased with the addition of the dam, the increase in groundwater storage was not sufficient to warrant the construction.  相似文献   

5.
Basin morphometric parameters play an important role in hydrological processes, as they largely control a catchment’s hydrologic response. Their analysis becomes even more significant when studying runoff reaction to intense rainfall, especially in the case of ungauged, flash flood prone basins. Unit hydrographs are one of the useful tools for estimating runoff when instrumental data are inadequate. In this work, instantaneous unit hydrographs based on the time-area method have been compiled along the drainage networks of two small rural catchments in Greece, situated approximately 25 km northeast of its capital, Athens. The two catchments drained by ephemeral torrents, namely Rapentosa and Charadros, have been subject to flash flooding during the last decades, which caused extensive damages at the local small towns of Marathon and Vranas. Hydrograph compilation in numerous locations along the catchments’ drainage networks directly reflected the runoff conditions across each basin against a given rainfall. This gave a holistic assessment of their hydrologic response, allowing the detection of areas where peak flow rates were elevated and therefore, there was higher flood potential. The resulting flood hazard zonation showed good correlation with locations of damages induced by past flood events, indicating that the method can successfully predict flood hazard spatial distribution. The whole methodology was based on geographic information software due to its excellent capabilities on storing and processing spatial data.  相似文献   

6.
The stable isotopes of oxygen and hydrogen were used to determine the seasonal contributions of precipitation to groundwater recharge at a forested catchment area in the upper North Han River basin, Korea. A comparison of the stable isotopic signatures of groundwater and precipitation indicates that the precipitations which occurred during both the dry and rainy seasons are the important source of groundwater recharge in this region. A stable isotopic signature shown in the stream waters at the upstream reaches is similar to that of groundwaters, indicating that stream waters are mostly fed by groundwater discharge. Reservoir waters in the downstream flood control dams have lower deuterium excess values or d-values compared with those of the upstream waters, indicating a secondary evaporative enrichment. These results can provide a basis for the effective management of groundwater and stream water resources in the North Han River basin.  相似文献   

7.
In recharge areas, the Heihe River flow was separated into components of ice-snowmelt and precipitation according to 14 gauging stations and to monthly hydrograph using oxygen-18. As shown by the result of the two-component mixing model, on average, 19.8% of the runoff comes from ice-snowmelt. At three stations which are closer to glaciers and with headstream of ice-snow melted water, the ice-snowmelt runoff is larger than 28% of stream water. In addition, because most of the ice-snowmelt infiltrates the groundwater, which later discharges into the river at mountain outlets, the ice-snowmelt percentage in runoff is lower than average at these stations with the elevation higher than 3,600 m. According to monthly hydrograph, the lowest percentage of ice-snowmelt in runoff is in July (6.46%), whereas during November it is the largest (26.1%). In the middle basin, the fraction of groundwater in runoff had a marked increase from 23.57% near Zhangye City to 60.28% near Gaotai City, and then a dramatic drop to 13.61% near Zhengyixia Station because of agricultural flood irrigation in Zhangye Basin.  相似文献   

8.
In the last decade, attention has been devoted to the southern part of the Egyptian Red Sea coast due to the large touristic and mining activities. Egypt spares no effort to develop it, to build new urban communities, and to create new job opportunities. Many comprehensive planning studies have been conducted. Many luxurious tourist spots, airports, and harbors have been constructed. These areas are subjected to flash floods, which represent a frequent threat to these urbanization activities that may cause losses in livelihood. By analyzing the geomorphologic features of the study area, intense stream networks are detected that, with the available metrological data, require flood management and analysis to mitigate the possible negative effects and to benefit from the estimation of flood water. Rahbaa basin is a sub-catchment of wadi Hodin. Flash floods within this area threaten the Red Sea coastal plain as well as the main coastal roads. It also directly drained out to the sea, which leads to a loss of huge amounts of flood water that is useful for arid regions. Using geographic information system and remote-sensing tools with the application of a comprehensive graphical modeling (watershed modeling system) supports the hydrological modeling of HEC-1. The total amount of runoff is calculated and the hydrograph of the 50-year return period is computed using rainfall historical data.  相似文献   

9.
High and variable levels of salinity were investigated in an intermittent stream in a high-rainfall area (～800 mm/year) of the Mt. Lofty Ranges of South Australia. The groundwater system was found to have a local, upslope saline lens, referred to here as a groundwater salinity ‘hotspot’. Environmental tracer analyses (δ18O, δ2H, 87/86Sr, and major elements) of water from the intermittent stream, a nearby permanent stream, shallow and deep groundwater, and soil-water/runoff demonstrate seasonal groundwater input of very saline composition into the intermittent stream. This input results in large salinity increases of the stream water because the winter wet-season stream flow decreases during spring in this Mediterranean climate. Furthermore, strontium and water isotope analyses demonstrate: (1) the upslope-saline-groundwater zone (hotspot) mixes with the dominant groundwater system, (2) the intermittent-stream water is a mixture of soil-water/runoff and the upslope saline groundwater, and (3) the upslope-saline-groundwater zone results from the flushing of unsaturated-zone salts from the thick clayey regolith and soil which overlie the metamorphosed shale bedrock. The preferred theory on the origin of the upslope-saline-groundwater hotspot is land clearing of native deep-rooted woodland, followed by flushing of accumulated salts from the unsaturated zone due to increased recharge. This cause of elevated groundwater and surface-water salinity, if correct, could be widespread in Mt. Lofty Ranges areas, as well as other climatically and geologically similar areas with comparable hydrogeologic conditions.  相似文献   

10.
Groundwater monitoring along the Romeriksporten tunnel, south-eastern Norway, provided an opportunity for studying the impacts of tunnelling on groundwater in fractured Precambrian gneiss rocks, and examining relations between bedrock hydrology, tectonic weakness zones and catchments. Tunnel leakage resulted in groundwater drawdown up to 35 m in weakness zones, converted groundwater discharge zones into recharge zones, and affected groundwater chemistry. The magnitude of drawdown and fluctuations in groundwater level differed between weakness zones, and varied with distance from the tunnel route, tunnel leakage, and recharge from catchments. Clear differences in groundwater level and fluctuation patterns indicated restricted groundwater flow between weakness zones. The groundwater drawdowns demonstrated coherent water-bearing networks to 180-m depth in faults and fracture zones. Similar groundwater levels with highly correlated fluctuations demonstrated hydraulic connectivity within fracture zones. Different groundwater drawdown and leakage in weakness zones with different appearance and influence of tectonic events demonstrated the importance of the geological history for bedrock hydrogeology. Water injection into the bedrock counteracted groundwater drawdowns. Even moderate leakage to underground constructions may lead to large groundwater drawdown in areas with small groundwater recharge. Hydrogeological interpretation of tectonic weakness zones should occur in the context of geological history and local catchment hydrology.  相似文献   

11.
Soil moisture balance studies provide a convenient approach to estimate aquifer recharge when only limited site-specific data are available. A monthly mass-balance approach has been utilized in this study to estimate recharge in a small watershed in the coastal bend of South Texas. The developed lumped parameter model employs four adjustable parameters to calibrate model predicted stream runoff to observations at a gaging station. A new procedure was developed to correctly capture the intermittent nature of rainfall. The total monthly rainfall was assigned to a single-equivalent storm whose duration was obtained via calibration. A total of four calibrations were carried out using an evolutionary computing technique called genetic algorithms as well as the conventional gradient descent (GD) technique. Ordinary least squares and the heteroscedastic maximum likelihood error (HMLE) based objective functions were evaluated as part of this study as well. While the genetic algorithm based calibrations were relatively better in capturing the peak runoff events, the GD based calibration did slightly better in capturing the low flow events. Treating the Box-Cox exponent in the HMLE function as a calibration parameter did not yield better estimates and the study corroborates the suggestion made in the literature of fixing this exponent at 0.3. The model outputs were compared against available information and results indicate that the developed modeling approach provides a conservative estimate of recharge.  相似文献   

12.
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater recharge rates. Timescales of recharge were defined by 1,873 distributed tritium measurements and 102 radiocarbon measurements from 27 well networks. Recharge rates ranged from?<?10 to 1,200?mm/yr in selected aquifers on the basis of measured vertical age distributions and assuming exponential age gradients. On a regional basis, recharge rates based on tracers of young groundwater exhibited a significant inverse correlation with mean annual air temperature and a significant positive correlation with mean annual precipitation. Comparison of recharge derived from groundwater ages with recharge derived from stream base-flow evaluation showed similar overall patterns but substantial local differences. Results from this compilation demonstrate that age-based recharge estimates can provide useful insights into spatial and temporal variability in recharge at a national scale and factors controlling that variability. Local age-based recharge estimates provide empirical data and process information that are needed for testing and improving more spatially complete model-based methods.  相似文献   

13.
黑河中游绿洲典型灌区地下水资源总均衡估算   总被引：6，自引：0，他引：6  
根据对研究区多年的水文地质观测资料的分析和研究,建立了黑河中游典型灌区地下水水资源总均衡模型,选取了黑河干流具有代表性的平川、板桥、鸭暖和蓼泉灌区,对地下水均衡模型中的补给项及排泄项的主要变量分别进行了估算,结果表明:各灌区均衡期内地下水动态资料计算的均衡期始末地下水储存量变化与模型计算的均衡差基本相近,其相对误差为-17.6%,说明均衡模型对于估算内陆绿洲灌区地下水资源均衡是比较准确的。  相似文献   

14.
我国南方岩溶管道流矿井涌水量计算问题较复杂。本文通过地下水动态过程曲线的均衡分析，以暗河排泄流量反求补给水量，并借河渠洪流估算理论预计矿井最大涌水量。由于对确定的数学模型，采用了集中参数系统和宏观求取参数的方法，使计算简便新颖。文中附有计算涌水量实例和矿井涌水量预测验证资料，表明方法的可靠性。  相似文献   

15.
Intense rainstorms in 2008 resulted in wide-spread flooding across the Midwestern United States. In Wisconsin, floodwater inundated a 17.7-km2 area on an outwash terrace, 7.5 m above the mapped floodplain of the Wisconsin River. Surface-water runoff initiated the flooding, but results of field investigation and modeling indicate that rapid water-table rise and groundwater inundation caused the long-lasting flood far from the riparian floodplain. Local geologic and geomorphic features of the landscape lead to spatial variability in runoff and recharge to the unconfined sand and gravel aquifer, and regional hydrogeologic conditions increased groundwater discharge from the deep bedrock aquifer to the river valley. Although reports of extreme cases of groundwater flooding are uncommon, this occurrence had significant economic and social costs. Local, state and federal officials required hydrologic analysis to support emergency management and long-term flood mitigation strategies. Rapid, sustained water-table rise and the resultant flooding of this high-permeability aquifer illustrate a significant aspect of groundwater system response to an extreme precipitation event. Comprehensive land-use planning should encompass the potential for water-table rise and groundwater flooding in a variety of hydrogeologic settings, as future changes in climate may impact recharge and the water-table elevation.  相似文献   

16.
Statistical approach to the analysis of the relationship between the frequency of flood events and land cover (LC) changes in small catchments of Slovakia is presented in this paper. The data for identification of LC changes were taken from the 1990 and 2006 CORINE LC (CLC) data layers. They were derived by computer-aided visual interpretation of satellite images under the CLC Projects. The data about frequency of flood events in small catchments are from the period 1996–2006. Two hypotheses were formulated: (1) the greater the area of LC changes, the more frequent flood events; (2) in catchments where LC changes accelerating formation of direct runoff (e.g. urbanization, deforestation, farming) dominates, flood events are more frequent than in catchments where the prevailing LC changes (e.g. afforestation) reduce formation of direct runoff. Validity of hypotheses was tested in the framework of flood potential of catchments by two-factor ANOVA method. The obtained results indicate that (1) flood event frequency increases with the increasing total area of LC changes in a catchment. This tendency clearly manifests itself in catchments with very high flood potential. It is somewhat less distinct in catchments with moderate and high flood potentials. (2) There were no differences in flood event frequency between the group of catchments, where LC changes accelerating the formation of the direct runoff prevailed and the group of catchments where LC changes decelerating the formation of direct runoff were dominated.  相似文献   

17.
In the Kushkak Valley (Khuzestan, Southwest Iran) an anticlinal structure has partially impounded an ephemeral stream. This natural impounded area has been chosen for an artificial recharge site due to its current rate of recharge, capability to store water and favorable situation for the construction of man-made barriers to stream flow. The aquifer to be recharged is the Kushkak unconfined aquifer which consists of medium to coarse-grained alluvial deposits that overlie consolidated conglomerate rock. In this semi-arid area with infrequent relatively heavy falls of rain, alluvial aquifer recharge can be an important process that sustains shallow, over-exploited groundwater bodies. In this investigation a multidisciplinary approach including: hydrometerological studies, and a detailed hydrogeochemical survey, have been carried out. Other essential prerequisite parameters for the scheme were also taken into account to determine the suitability of this location for groundwater artificial recharge. The assessment has brought out that (1) the proposed reservoir will conserve a major part of the water being lost, (2) annual runoff of about 0.27 MCM can be injected into the aquifer through recharge from impounded water, (3) hydrochemical data from surface water and from the Kushkak aquifer water demonstrates that dilution and change in compositional trend in the groundwater proximal to the impounded alluvial bed areas would be expected based on the infiltration capacity of this site, and (4) cost–benefit ratio of the project is 1:2 and it is assumed to recover the investment within six years.  相似文献   

18.
An integrated approach using hydrogeochemical analysis, remote sensing, GIS, and field data was employed to characterize the groundwater resources in southern Wadi Qena, Egypt. Various thematic maps showing topography, lineaments, wadi deposits, slope, and stream networks were combined through GIS analysis to discriminate groundwater potential zones on the valley floor. The resulting map classifies the area into five groups of groundwater potentiality from very high to very low zones, supported by the groundwater level, well locations, and by the results of previous geophysical studies. Thirty-seven groundwater well data were tested from the Quaternary and Nubian Sandstone aquifers and analyzed for physio-chemical parameters. Results of hydrochemical analysis show that water quality varies widely through the aquifers, and groundwater in the Quaternary aquifer shows the highest salinity values and a predominance of Na and Cl in water chemical facies. Overlay GIS maps of alkalinity (SAR and RSC) and salinity hazards (EC and Cl) of the Quaternary aquifer were prepared. The resulting maps show that samples do not present an alkalinity hazard in most areas but are potentially salinity hazard. Therefore, the water is fit for agricultural use with certain restrictions, but is not suitable for direct human consumption because it is either very hard or too saline.  相似文献   

19.
Atmospheric deposition of S in Sweden has decreased by some 80% over the last 15 a, resulting in a general reduction of SO4 concentrations in ground and surface water. This project, however, shows that artificial hydrological alteration in an acid wetland can reverse this trend and increase acidity and SO4 concentrations. The experiment involved the monitoring of two catchments in relatively virgin conditions. In one of the catchments, an experiment with intensive groundwater extraction from the bedrock was carried out. During the experiment, the runoff from the catchment decreased by 50%. Furthermore, the extraction of groundwater resulted in increased seasonal aeration of the centrally located wetland, leading to oxidation of reduced S bound to the soil layers of the wetland. The S changed to solute SO4, with a subsequent SO4 surge. Thus, the experiment resulted in an induced acidification of the wetland and runoff waters. The extraction of groundwater significantly increased the recharge of water from the overburden, glacial till and organic soils to groundwater in the bedrock, which in turn reduced the retention time in the bedrock aquifer. These changes resulted in the chemical signature of the groundwater in the bedrock becoming similar to those of the wetland. The findings revealed deterioration in the water quality in the bedrock due to increased concentrations of dissolved organic C and SO4, as well as a decrease in pH.  相似文献   

20.
近年来,无资料或资料缺乏地区汇流计算成为水文研究热点。基于地形参数的地貌瞬时单位线(GIUH)方法凭借其对历史降雨径流实测资料的不依赖性,已然成为径流模拟研究中被普遍采用且效果较好的方法之一。为探讨江苏省无资料山丘区的径流模拟方法,选取具有典型地形地貌特征的镇江通胜洛阳河小流域展开研究。根据地貌特征值等数据提取出该流域的地貌单位线,采用地貌单位线计算径流过程,利用2016、2017年汛期实测的4场洪水进行方法验证,将计算径流与实测数据进行对比分析,结果表明:基于地貌特征的地貌单位线法在该流域洪水模拟中具有较高精度,又因该流域于江苏省乃代表性区域,初步判定可将该方法推广至其他无资料山丘区流域。  相似文献   

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