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1.
Whether groundwater resources can be sustainably utilized is largely determined and characterized by hydrogeological parameters.Estimating the groundwater recharge is one of the essential parameters for managing water resources and protecting water resources from contamination.This study researched the spatial and temporal variation of groundwater recharge in the Thepkasattri sub-district through integrating chloride mass balance(CMB)and water table fluctuation(WTF)methods.The chloride content of representative rainfall and groundwater samples was analyzed.Besides,WTF method was adopted from groundwater level data from 2012 to 2015.According to the CMB method,the mean recharge was estimated to be 1172 mm per year,accounting for 47%of the annual rainfall.Moreover,the estimated recharge from the WTF method took 26%of annual rainfall in 2015.The recharge was underestimated according to the WTF method,because of the uncertainty in specific yield estimates and the number of representative wells in the study area.Moreover,the correlation between rainfall and water table fluctuation data indicated the positive linear relationship between two parameters.The spatial recharge prediction indicated that recharge was higher(1200-1400 mm/yr)in the eastern and western catchment,while that in the central floodplains was between 800 mm/yr and 1100 mm/yr.In addition,low recharge value between 450 mm/yr and 800 mm/yr was observed in the south-west part of Thepkasattri.The spatial variation of recharge partly reflects the influences of land use and land cover of the study area.  相似文献   

2.
A time-series approach to the estimation of recharge rate in unconfined aquifers of highly variable water level is proposed. The approach, which is based on the water-table fluctuation method (WTF), utilizes discrete water-level measurements. Other similar techniques require continuous measurements, which makes them impossible to apply in cases where no data from automatic loggers are available. The procedure is deployed at the Ressacada Farm site, southern Brazil, on a coastal shallow aquifer located in a humid subtropical climate where diurnal water-level variations of up to 1 m can follow a precipitation event. The effect of tidal fluctuations on the groundwater levels is analyzed using a harmonic component builder, while a time-variable drainage term is evaluated through an independent analysis and included in the assessment. The estimated recharge values are compared with those obtained from the continuous measurements showing a good agreement with the approaches for discrete dataset intervals of up to 15 days. Subsequently, the estimated recharge rates are incorporated into a transient groundwater-flow model and the water levels are compared showing a good match. Henceforth, the approach extends the applicability of WTF to noncontinuous water-level datasets in groundwater recharge studies.  相似文献   

3.
Radon has been used to determine groundwater velocity and groundwater discharge into wetlands at the southern downstream boundary of the Crau aquifer, southeastern France. This aquifer constitutes an important high-quality freshwater resource exploited for agriculture, industry and human consumption. An increase in salinity occurs close to the sea, highlighting the need to investigate the water balance and groundwater behavior. Darcy velocity was estimated using radon activities in well waters according to the Hamada “single-well method” (involving comparison with radon in groundwater in the aquifer itself). Measurements done at three depths (7, 15 and 21 m) provided velocity ranging from a few mm/day to more than 20 cm/day, with highest velocities observed at the 15-m depth. Resulting hydraulic conductivities agree with the known geology. Waters showing high radon activity and high salinity were found near the presumed shoreline at 3,000 years BP, highlighting the presence of ancient saltwater. Radon activity has also been measured in canals, rivers and ponds, to trace groundwater discharges and evaluate water balance. A model of the radon spatial evolution explains the observed radon activities. Groundwater discharge to surface water is low in pond waters (4 % of total inputs) but significant in canals (55 l/m2/day).  相似文献   

4.
A study of environmental chloride and groundwater balance has been carried out in order to estimate their relative value for measuring average groundwater recharge under a humid climatic environment with a relatively shallow water table. The hybrid water fluctuation method allowed the split of the hydrologic year into two seasons of recharge (wet season) and no recharge (dry season) to appraise specific yield during the dry season and, second, to estimate recharge from the water table rise during the wet season. This well elaborated and suitable method has then been used as a standard to assess the effectiveness of the chloride method under forest humid climatic environment. Effective specific yield of 0.08 was obtained for the study area. It reflects an effective basin-wide process and is insensitive to local heterogeneities in the aquifer system. The hybrid water fluctuation method gives an average recharge value of 87.14 mm/year at the basin scale, which represents 5.7% of the annual rainfall. Recharge value estimated based on the chloride method varies between 16.24 and 236.95 mm/year with an average value of 108.45 mm/year. It represents 7% of the mean annual precipitation. The discrepancy observed between recharge value estimated by the hybrid water fluctuation and the chloride mass balance methods appears to be very important, which could imply the ineffectiveness of the chloride mass balance method for this present humid environment.  相似文献   

5.
以辽宁省平原区为研究背景,建立了典型区地下水系统数学模型。提出了可变的开采含水层等效渗透系数和平均给水度的水文地质参数模拟方法,对常规分区法进行了改进,并应用于建立的数学模型中,提高了模型精度。用修正有限元法对数学模型进行数值离散,利用Visual Basic软件编制计算程序,对地下水系统进行模拟,取得了较好的模拟结果。建立的模型为进一步研究辽宁省平原区地下水状况和可持续利用提供了条件,研究方法对同类地区的模型研究具有重要参考价值。  相似文献   

6.
Groundwater flow in the Leon-Chinandega aquifer was simulated using transient and steady-state numerical models. This unconfined aquifer is located in an agricultural plain in northwest Nicaragua. Previous studies were restricted to determining groundwater availability for irrigation, overlooking the impacts of groundwater development. A sub-basin was selected to study the groundwater flow system and the effects of groundwater development using a numerical groundwater flow model (Visual MODFLOW). Hydrological parameters obtained from pumping tests were related to each hydrostratigraphic unit to assign the distribution of parameter values within each model layer. River discharge measurements were crucial for constraining recharge estimates and reducing the non-uniqueness of the model calibration. Steady-state models have limited usefulness because of the major variation of recharge and agricultural pumping during the wet and dry seasons. Model results indicate that pumping induces a decrease in base flow, depleting river discharge. This becomes critical during dry periods, when irrigation is highest. Transient modeling indicates that the response time of the aquifer is about one hydrologic year, which allows the development of management strategies within short time horizons. Considering further development of irrigated agriculture in the area, the numerical model can be a powerful tool for water resources management.  相似文献   

7.
Pollution and overexploitation of scarce groundwater resources is a serious problem in the Zarqa River catchment, Jordan. To estimate this resource’s potential, the amount and spatial distribution of groundwater recharge was calculated by applying the hydrological model J2000. The simulation period is composed of daily values gathered over a 30-year period (July 1977 to June 2007). The figure finally obtained for estimated groundwater recharge of the Zarqa River catchment is 105 × 106 m3 per year (21 mm a?1). This is 19 % higher than the value previously assumed to be correct by most Jordanian authorities. The average ratio of precipitation to groundwater recharge is 9.5 %. To directly validate modelled groundwater recharge, two independent methods were applied in spring catchments: (1) alteration of stable isotope signatures (δ18O, δ2H) between precipitation and groundwater and (2) the chloride mass balance method. Recharge rates determined by isotopic investigations are 25 % higher, and recharge rates determined by chloride mass balance are 9 % higher than the modelled results for the corresponding headwater catchments. This suggests a reasonably modelled safe yield estimation of groundwater resources.  相似文献   

8.
Modeling of groundwater flow for Mujib aquifer, Jordan   总被引：4，自引：0，他引：4  
Jordan is an arid country with very limited water resources. Groundwater is the main source for its water supply. Mujib aquifer is located in the central part of Jordan and is a major source of drinking water for Amman, Madaba and Karak cities. High abstraction rates from Mujib aquifer during the previous years lead to a major decline in water levels and deterioration in groundwater quality. Therefore, proper groundwater management of Mujib aquifer is necessary; and groundwater flow modeling is essential for proper management. For this purpose, Modflow was used to build a groundwater flow model to simulate the behavior of the flow system under different stresses. The model was calibrated for steady state condition by matching observed and simulated initial head counter lines. Drawdown data for the period 1985–1995 were used to calibrate the transient model by matching simulated drawdown with the observed one. Then, the transient model was validated by using drawdown data for the period 1996–2002. The results of the calibrated model showed that the horizontal hydraulic conductivity of the B2/A7 aquifer ranges between 0.001 and 40m/d. Calibrated specific yield ranges from 0.0001 to 0.15. The water balance for the steady state condition of Mujib aquifer indicated that the total annual direct recharge is 20.4 × 106m3, the total annual inflow is 13.0 × 106 m3, springs discharge is 15.3 × 106 m3, and total annual outflow is 18.7 × 106 m3. Different scenarios were considered to predict aquifer system response under different conditions. The results of the sensitivity analysis show that the model is highly sensitive to horizontal hydraulic conductivity and anisotropy and with lower level to the recharge rates. Also the model is sensitive to specific yield  相似文献   

9.
Groundwater resource potential is the nation’s primary freshwater reserve and accounts for a large portion of potential future water supply. This study focused on quantifying the groundwater resource potential of the Upper Gilgel Gibe watershed using the water balance method. This study began by defining the project area’s boundary, reviewing previous works, and collecting valuable primary and secondary data. The analysis and interpretation of data were supported by the application of different software like ArcGIS 10.4.1. Soil water characteristics of SPAW (Soil-plant-air-water) computer model, base flow index (BFI+3.0), and the water balance model. Estimation of the areal depth of precipitation and actual evapotranspiration was carried out through the use of the isohyetal method and the water balance model and found to be 1 664.5 mm/a and 911.6 mm/a, respectively. A total water volume of 875 829 800 m3/a is estimated to recharge the aquifer system. The present annual groundwater abstraction is estimated as 10 150 000 m3/a. The estimated specific yield, exploitable groundwater reserve, and safe yield of the catchment are 5.9%, 520 557 000 m3/a, and 522 768 349 m3/a respectively. The total groundwater abstraction is much less than the recharge and the safe yield of the aquifer. The results show that there is a sufficient amount of groundwater in the study area, and the groundwater resources of the area are considered underdeveloped.  相似文献   

10.
基于地下水流数值模型的改进DRASTIC方法   总被引：1，自引：0，他引：1       下载免费PDF全文
地下水脆弱性评价作为地下水资源保护和地下水开发利用规划的一个重要工具,被广泛的应用于实际工作中。尝试利用地下水数值模型为改进的DRASTIC方法提供数据支持,并以北京市平原区为例探讨地下水脆弱性评价方法。评价结果与传统方法在高值区和低值区具有很好的对应性,而基于模型的方法在地下水水位计算、含水层介质和水力传导系数确定上较传统方法更具优势,如地下水位的计算上较传统方法更为客观地体现含水介质对地下水运动的影响,且能够方便地获得模拟期内任意时间的流场数据;经由模型调试后的含水层参数数据,较传统方法更为准确。评价结果分区之间的变化较传统方法更为平滑,更符合水文地质条件渐变的特性。  相似文献   

11.
Groundwater recharge was investigated in the most extensive sand and gravel aquifer (area of approximately 200 km2) in the Republic of Ireland as part of a wider study seeking to derive recharge estimates using aquifer vulnerability mapping. The proportion of effective rainfall (total rainfall minus actual evapotranspiration) that leads to recharge is known as the recharge coefficient. The recharge investigation involved a variety of approaches, including soil moisture budgeting, well hydrograph analysis, numerical modelling and a catchment water balance. The adoption of multiple techniques provided insights on recharge and also on aquifer properties. Comparison of two soil moisture budgeting approaches (FAO Penman-Monteith with Penman-Grindley) showed how variations in the effective rainfall values from these methods influence groundwater levels simulated in a numerical groundwater model. The catchment water balance estimated the recharge coefficient to be between 81 and 85%, which is considered a reasonable range for this aquifer, where overland flow is rarely observed. The well hydrograph analysis, using a previous estimate of specific yield (0.13), gave recharge coefficients in the range of 40–80%, considered low for this aquifer: a revised specific yield of 0.19 resulted in a more reasonable range of recharge coefficients of between 70 and 100%.  相似文献   

12.
An integrated GIS-based approach for establishing a spatial and temporal prediction system for groundwater flow and land subsidence is proposed and applied to a subsidence-progressed Japanese coastal plain. Various kinds of fundamental data relating to groundwater flow and land subsidence are digitized and entered into a GIS database. A surface water hydrological cycle simulation is performed using a GIS spatial data operation for the entire plain, and the spatial and temporal groundwater infiltration quantity is hereby obtained. Through the data transformation from the GIS database to a groundwater flow code (MODFLOW), a 3D groundwater flow model is established and unsteady groundwater flow simulation for the past 21 years is conducted with results which compare satisfactorily with observed results. Finally, a Visual Basic code is developed for land subsidence calculations considering aquifer and aquitard deformation. Future land subsidence in the plain is predicted assuming different water pumping scenarios, and the results provide important information for land subsidence mitigation decision-making.  相似文献   

13.
In addition to spatial distribution of groundwater-flow parameters, aquifer properties of location and shape are also significant for assessing groundwater resources because they strongly affect water flow. We present a selection of geologic data suitable for aquifer analysis, a mathematical method of processing them, and a combination of several maps produced by it. The data used in the analysis are typically obtained by borehole investigation. Our targets are the areas underlain by geologic bodies with different ages and lithologies; the spatial correlation structures of geologic data over the areas tend to change locally. The processing method should be a versatile one that is applicable to areas where geostatistical stationarity is not satisfied. The aquifer analysis consistent with that requirement consists of two steps: the first is the transformation of screen locations, locations of sand and gravel layers, and resistivity by electric logging into indicator values, and the second is three-dimensional interpolation of these using the optimization principle method to produce three kinds of distribution models. A stochastic simulation is also used for modeling the resistivity distribution. The three distribution models are integrated to generate a value for evaluating the possibility of aquifer existence. A case study of an alluvial coastal plain, situated in southwest Japan, describes an aquifer model that contains three permeable layers. Each layer has about 10-m thickness and is lens shaped. To confirm the validity of the model, we have drilled two wells that reached one of the middle and bottom permeable layers, observing the water level change. Low correlation of the temporal changes of levels between the wells indicates that the two layers are hydrologically independent of each other. Additionally, groundwater-flow patterns have been estimated by transforming the simulation model parameter into hydraulic conductivity through a simple function and using a finite difference method for flow analysis. The procedure proposed by this study can be applied to other areas by changing the weights assigned to each geologic and geotechnical factor in the generation of the coefficient for aquifer existence, considering the reliability of each factor and hydrologic properties of study area.  相似文献   

14.

Three-dimensional transient groundwater flow and saltwater transport models were constructed to assess the impacts of groundwater abstraction and climate change on the coastal aquifer of Tra Vinh province (Vietnam). The groundwater flow model was calibrated with groundwater levels (2007–2016) measured in 13 observation wells. The saltwater transport model was compared with the spatial distribution of total dissolved solids. Model performance was evaluated by comparing observed and simulated groundwater levels. The projected rainfalls from two climate models (MIROC5 and CRISO Mk3.6) were subsequently used to simulate possible effects of climate changes. The simulation revealed that groundwater is currently depleted due to overabstraction. Towards the future, groundwater storage will continue to be depleted with the current abstraction regime, further worsening in the north due to saltwater intrusion from inland trapped saltwater and on the coast due to seawater intrusion. Notwithstanding, the impact from climate change may be limited, with the computed groundwater recharge from the two climate models revealing no significant change from 2017 to 2066. Three feasible mitigation scenarios were analyzed: (1) reduced groundwater abstraction by 25, 35 and 50%, (2) increased groundwater recharge by 1.5 and 2 times in the sand dunes through managed aquifer recharge (reduced abstraction will stop groundwater-level decline, while increased recharge will restore depleted storage), and (3) combining 50% abstraction reduction and 1.5 times recharge increase in sand dune areas. The results show that combined interventions of reducing abstraction and increasing recharge are necessary for sustainable groundwater resources development in Tra Vinh province.

  相似文献   

15.
The groundwater flow system and the flow velocity in the alluvial fan plain of the Hutuo River, China, have been studied, with an emphasis on relating geochemical characteristics and isotopes factors. Seven stretches of one river, six springs and 31 wells, with depths ranging from 0 m (river waters) to 150 m, were surveyed. The groundwater has a vertical two-layer structure with a boundary at about 80–100 m depth, yielding an upper and a lower groundwater layer. The δ18O and δD values range from ?10.56 to ?7.05‰ and ?81.83 to ?59‰, respectively. The groundwater has been recharged by precipitation, and has not been subjected to significant evaporation during infiltration into the aquifer in the upper layer. Using a tritium model, the groundwater flow in the alluvial fan plain showed horizontal flow velocity to be greater than vertical velocity. Groundwater in the upper layer is characterized by Ca–HCO3 type. From the spatial distribution characteristics of the stable isotope and chemical composition of the groundwater, agricultural irrigation was considered to have an influence on the aquifer by causing excessive groundwater abstraction and irrigation return.  相似文献   

16.
Karst aquifers can have a complex flow as a result of the formation of large conduits from dissolution features. As a result, a three-dimensional finite-difference groundwater flow model (equivalent porous media) may not apply as the dual porosity nature of karst features and the effects of turbulent flow cannot be directly simulated. Statistical analysis of karst hydrographs of the Trifilia aquifer in Greece showed the existence of a slightly karstified mass with high primary porosity that regulates the flow. An equivalent porous media model was developed to simulate the Trifilia karst aquifer using MODFLOW. Steady state and transient state calibration gave encouraging results for the equivalent porous media approach, which does not consider pipe flow or turbulence. Detailed hydrogeological research conducted in the area helped define the aquifer hydraulic conductivity zones and extent; and flux to/from the aquifer. Only hydraulic conductivity and specific yield were adjusted during calibration, as the flux to/from the system was considered known and applied as boundary conditions. Small mean absolute and RMS piezometric head error of the model under both steady and transient state conditions were achieved.  相似文献   

17.
The unconfined aquifer supported by the extensive Holocene coastal plain of southern Brazil is found dissected at several places by tidally forced streams. One such unit of coastal plain, falling within the watershed limits of Perequê Stream in Paraná state, was analyzed using MODFLOW to assess the surface and subsurface water components under different stress conditions. The steady-state simulation suggests that ~23,000 m3/day of water forms the total budget of the designated aquifer zone and this zone discharges ~16,000 m3/day across the interface between the freshwater aquifer zone and the sea as direct submarine discharge. The maximum evaporation loss was assumed to be 2,700 m3/day. Any change in effective aquifer storage was insignificant, as there is no large-scale exploitation of local groundwater reserves. A calibration exercise, based on field measurements lasting 1 year, supports validity of the model considered. Simulations representing two different transient conditions point to the dynamic hydraulic response exhibited by the aquifer. A schematic map, showing directions and velocity of subsurface flows, and a three-dimensional model of the groundwater reserve helped to visualize the hydrogeologic changes and to formulate management plans.  相似文献   

18.
区域地下水系统防污性能评价,面临影响因子多又复杂、评价指标难以客观性选定和权重不易确定等难题,以至严重影响评价结果的可信性。本文以鲁北平原为例,在以往地下水脆弱性评价常用的DRASTIC模型基础上,采用创新的迭置指数方法,改进为"DRITCS法",选择地下水位埋深、包气带综合岩性、地表2 m内单层厚度大于0.5 m的粘土层厚、含水砂层厚度及其渗透系数、和地下水净补给量等因子,组成区域地下水系统防污性能评价模型。合理地确定了区域地下水系统防污性能评价中关键指标——包气带粘性土层变化影响,并在鲁北平原示范性应用和通过以面源污染为主的三氮污染现状验证的结果表明:本文提出的方法能够客观地反映流域性相变造成的地下水系统防污性能空间差异性和区位分布特征,具有较强的实用性。  相似文献   

19.
This study evaluates the alternative conceptual models for groundwater modelling. A true model was created with a synthetic alluvial fan-plain hydrogeological framework. Various alternative conceptual models were evaluated for groundwater flow simulations. The first alternative model is a single aquifer layer model; the second alternative model is a 3-layer aquifer model; and the third model is a 5-layer model consisting of 3 aquifers separated by 2 aquitards. All models could fit very well to the observations with optimized values of hydraulic conductivities. However, the single aquifer layer model can only compute water balance components with good accuracy. The 3-layer aquifer model can be used for water balance computation and groundwater head simulation with small errors. The 5-layer model is capable of simulating water budget, groundwater head distribution and travel times with high accuracy. Multi-model analysis found only the 3rd alternative model superior.  相似文献   

20.
李霞  文章  梁杏  马腾  陈晨 《地球科学》2017,42(5):743-750
含水层的水文地质参数是进行地下水资源计算、地下水污染防控等所必需的基础数据,结合数值模拟技术进行含水层参数反演很有必要.按照1:5万水文地质调查规范在江汉平原仙桃市杨林尾镇复兴水厂不同含水层位开展抽水试验,包括深层含水层单孔抽水试验以及浅层含水层中群孔(2孔)抽水试验.对于单孔抽水试验,应用第1类越流系统井流理论进行参数反演;对于群孔抽水试验,推导了特定综合井函数,并利用特定标准曲线匹配法和直线图解法求解了含水层参数.随后利用FEFLOW软件建立了相应数值模型,拟合了含水层参数.结果表明:浅层含水层的渗透系数变化范围为21.66~54.00 m/d,贮水率变化范围为1.28×10-5~8.00×10-4 m-1;深层含水层渗透系数变化范围为1.27~7.00 m/d,贮水率变化范围为3.90×10-6~5.00×10-6 m-1.对于深层承压含水层而言,越流补给量较大.采用数值模拟方法结合抽水试验数据求参,综合考虑了含水层结构,拟合效果好,所得结果更加可靠.   相似文献   

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