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1.
Compensation pumping is used to alleviate deficiencies in streamflow discharge during dry seasons. Short-term groundwater pumping can use aquifer storage instead of catchment-zone water until the drawdown reaches the edge of the stream. The capacitance is a complex, dimensionless parameter of an aquifer system that defines the delayed effect on streamflow when there is groundwater pumping. This parameter is a function of aquifer hydraulic characteristics, pumping time, and distance between the well and stream edge; the latter can involve stream leakance and vertical leakance of an associated aquitard. Three typical hydraulic cases of combined water systems (major catchment-zone wells close to the stream and compensation pumping wells) were classified depending on their capacitance structure (i.e. the relationship between surface water and groundwater): (1) perfect hydraulic connection between the stream and aquifer; (2) imperfect hydraulic connection between the stream and aquifer; and (3) essentially imperfect hydraulic connection between the stream and the underlying confined aquifer. The impact of various hydraulic characteristics and engineering factors on stream depletion was examined by conceptual and numerical modeling. To predict the suitability and efficiency of a combined water system application, regression tests were undertaken on unit stream depletion and capacitance, and power dependencies were defined.  相似文献   

2.
Groundwater pumping and changes in climate-induced recharge lead to lower groundwater levels and significant changes in the water balance of a catchment. Water previously discharged as evapotranspiration can become a source of pumpage. Neglecting this effect leads to overestimated streamflow depletion. A small river basin (Sudogda River Basin, Russia) with a boreal climate and with long-term records of groundwater head and streamflow rate (showing that the measured stream depletion is less than the pumping rate) was investigated. The role of evapotranspiration in the water balance was analyzed by a hydrogeological model using MODFLOW-2005 with the STR package; the annual variation in recharge was obtained with the codes Surfbal and HYDRUS. The Sudogda River Basin was classified according to landscape and unsaturated-zone texture classes, and for each classified zone, the unsaturated-zone flow simulation was used to calculate the annual recharge dynamics for the observation period. Calibration of the regional flow model was conducted using flow and head observations jointly for two steady-state flow conditions—natural (before pumping started) and stressed (pumping). The simulations showed that pumped water originates from three sources: intercepted baseflow (75% of the annual total pumping rate), the capture of groundwater evapotranspiration discharge plus increased groundwater recharge (17%), and induced stream infiltration (8%). Additionally, multi-year precipitation records were analyzed to detect any long-term recharge and pumping water-budget changes. The results showed that increasing groundwater recharge by natural precipitation leads to (1) decreased intercepted baseflow and induced streamflow infiltration and (2) increased intercepted evapotranspiration discharge, thereby reducing stream depletion.  相似文献   

3.
The Mancha Oriental System (MOS, 7,260?km2) is one of the largest aquifers within Spain, and is encompassed by the Jucar River Basin. Over the past 30?years, socioeconomic development within the region has been largely due to intensive use of groundwater resources for irrigating crops (1,000?km2). Groundwater pumping (406 million m3/year) has provoked a steady drop in the groundwater level and a reduction of MOS discharge to the Jucar River. The study aims to characterize the river?Caquifer relationship, to determine the influence that groundwater abstraction has on the river discharge. This research has advanced a three-dimensional large-scale numerical groundwater-flow model (MODFLOW 2000) in order to spatially and temporally evaluate, quantify and predict the river?Caquifer interactions that are influenced by groundwater abstraction in MOS. It is demonstrated that although groundwater abstraction increased considerably from the early 1980s to 2000, the depletion of water stored in the aquifer was lower than might be expected. This is mainly due to aquifer recharge from the Jucar River, induced by groundwater abstraction. The area of disconnection between the river and the water table (i.e. where groundwater head is lower than the riverbed) is found to have spread 20?km downstream from its position before pumping started.  相似文献   

4.
把城市污水净化处理为符合回灌标准的再生水并安全回灌补给地下水, 对于实现污水资源化、含水层恢复、缓解我国水资源供需矛盾和环境污染态势具有重要意义.针对再生水回灌地下水存在的水质安全问题, 通过理论分析、系列实验和技术集成形成了再生水地表回灌补给地下水的水质安全保障体系及关键技术.该安全保障体系包括场地选择与勘查、高效低成本的再生水处理技术、土壤—含水层系统数学模型和回灌方案设计技术、水质监控系统、安全评价技术以及回灌管理法规等.这些要素相互依赖、相互作用, 构成一个完整的体系.郑州郊区示范工程证实了该水质安全保障体系的可行性.2年示范工程表明, 处理的再生水水质达到《城市污水再生利用地下水回灌水质》(GB/T 19772-2005)标准, 优于场地背景地下水水质, 补给含水层后的地下水基本达到《地下水质量标准》(GB/T 14818-1993)Ⅲ类水标准.建议有关政府部门把再生水利用及回灌补给地下水, 纳入水资源开发利用及环境保护规划的整体框架中, 尽快制定或完善再生水回灌补给地下水的相关法律、法规和标准体系, 建立再生水回灌许可证制度, 有序推进再生水回灌工程.   相似文献   

5.
A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ～80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.  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.
Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997–2006, followed by validation (2007–2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems.  相似文献   

8.
The paper aims at evaluating the interaction between ground and surface water along the Langat River in Malaysia through the development of a numerical simulation. Malaysia has been experiencing a rapid economic growth since the last few decades, driven by many factors such as agriculture, industry, and the like. The demand for water in these sectors has increased so tremendously that surface water has been utilized in conjunction to groundwater. Approximately 18,184 m3 of water per day is obtained from the aquifer to supply to the steel factory. There are also workshops, petroleum stations, and houses in the area thus causing the water quantity and quality to degrade. In terms of quantity, the pumping activity has altered the interaction between the groundwater and surface water. Therefore, a numerical model was proposed and two aquifer layers were simulated, with the first layer being approximately >20 m in depth and the second layer >100 m. The recharge estimated from the tank model was input into the groundwater modeling. The effects of the surface water to the aquifer were included in the simulation by defining the river conductance, river bed, and river level. The calibrated model (error about 0.9 m) was achieved and applied to predict the flow pattern in its natural state without the pumping and with the pumping states. As a result, in the first scenario, the stream was in an effluent condition influenced by the groundwater from the northeast to the west. A hyporheic flow occurred and was observed from the contour map. The flow system was changed in the second scenario when the pumping activity was included in the simulation. The groundwater lost its original function but received leakage from the stream near the pumping sites. The findings of this study will help the local authorities and other researchers to understand the aquifer system in the area and assist in the preparation of a sustainable groundwater management.  相似文献   

9.
The study area Hindon -Yamuna interfluve region is underlain by a thick pile of unconsolidated Quaternary alluvial deposits and host multiple aquifer system. Excessive pumping in the last few decades, mainly for irrigation, has resulted in a significant depletion of the aquifer. Therefore, proper groundwater management of Hindon-Yamuna interfluve region is necessary. For effective groundwater management of a basin it is essential that careful zone budget study should be carried out. Keeping this in view, groundwater flow modelling was attempted to simulate the behavior of flow system and evaluate zone budget. Visual MODFLOW, pro 4.1 is used in this study to simulate groundwater flow. The model simulates groundwater flow over an area of about 1345 km2 with a uniform grid size of 1000 m by 1000 m and contains three layers, 58 rows and 37 columns. The horizontal flows, seepage losses from unlined canals, recharge from rainfall and irrigation return flows were applied using different boundary packages available in Visual MODFLOW, pro 4.1. The river — aquifer interaction was simulated using the river boundary package. Simulated pumping rates of 500 m3/day, 1000 m3/day and 1500 m3/day were used in the pumping well package.The zone budget for the steady state condition of study area indicated that the total annual direct recharge is 416.10 MCM and the total annual groundwater draft through pumping is of the order of 416.63 MCM. Two scenarios were considered to predict aquifer system response under different conditions. Sensitivity analysis on model parameters was conducted to quantitatively evaluate the impact of varying model inputs. Based on the results obtained from the sensitivity analysis, it was found that the model is more sensitive to hydraulic conductivity and recharge parameter. Present study deals with importance of groundwater modelling for planning, design, implementation and management of groundwater resources.  相似文献   

10.
陆徐荣  杨磊  陆华 《江苏地质》2014,38(2):293-297
从淮河江苏段与地下水含水层关系出发,认为淮河河床切割了地下水承压含水层。地下水的水动力特征表明地下水接受了淮河水的补给。从水质研究的角度印证了地表水与地下水的补排关系。将淮河水与潜水、微承压、承压水之间进行聚类分析,印证了微承压、承压水与淮河水同源。  相似文献   

11.
In arid regions of western China, water resources come from mountain watersheds and disappear in the desert plain. The exchange of surface water and groundwater takes place two or three times in a basin. It is essential to analyze the interaction of groundwater with surface water to use water resources effectively and predict the change in the water environment. The conventional method of analysis, however, measures only the flow of a stream and cannot determine groundwater seepage accurately. As the concentration of Radon-222 (222Rn) in groundwater is much higher than in surface water, the use of 222Rn was examined as an indicator for the analysis of the interaction between surface water and groundwater. Measurement of the 222Rn concentration in surface water was conducted to detect groundwater seepage into a stream in the middle Heihe Basin of northwestern China. Furthermore, the simultaneous groundwater flow into and out of a stream from the aquifers was quantified by solving the 222Rn mass balance equation, in which the losses of gas exchange and radioactive decay of 222Rn are considered. Meanwhile, river runoff was gauged to determine the exchange rates between surface water and groundwater. The result shows that 222Rn isotope can be used as a good environmental tracer with high sensitivity for the interaction between surface water and groundwater, especially in the fractured aquifer system, karst aquifer system and discharge basins.  相似文献   

12.
Identification and quantification of groundwater and surface-water interactions provide important scientific insights for managing groundwater and surface-water conjunctively. This is especially relevant in semi-arid areas where groundwater is often the main source to feed river discharge and to maintain groundwater dependent ecosystems. Multiple field measurements were taken in the semi-arid Bulang sub-catchment, part of the Hailiutu River basin in northwest China, to identify and quantify groundwater and surface-water interactions. Measurements of groundwater levels and stream stages for a 1-year investigation period indicate continuous groundwater discharge to the river. Temperature measurements of stream water, streambed deposits at different depths, and groundwater confirm the upward flow of groundwater to the stream during all seasons. Results of a tracer-based hydrograph separation exercise reveal that, even during heavy rainfall events, groundwater contributes much more to the increased stream discharge than direct surface runoff. Spatially distributed groundwater seepage along the stream was estimated using mass balance equations with electrical conductivity measurements during a constant salt injection experiment. Calculated groundwater seepage rates showed surprisingly large spatial variations for a relatively homogeneous sandy aquifer.  相似文献   

13.
根据焉耆盆地开都河水及其两岸地下水中的氢氧稳定同位素资料及氘过量参数(d)值,分析了焉耆盆地内不同水体的δ(D)、δ(18O)和d值的分布规律,并得到地下水的主要补给来源及其与开都河水的相互作用关系;地下水的δ(D)在-87.60‰～-61.82‰间,δ(18O)在-10.90‰～-9.73‰间;开都河水的δ(D)在-71.95‰～-58.58‰间,δ(18O)在-9.57‰～-8.64‰间。结果表明:焉耆盆地内地下水和地表水同源于山区的降水和冰雪融水,且经历了较强的蒸发作用;地下水与地表水之间的直接水力联系较弱,深层地下水主要接受开都河水在洪积扇区的入渗补给,浅层地下水主要接受河流引水灌溉入渗;不同深度地下水之间的水力联系较为密切,为统一的地下水系统。  相似文献   

14.
The response of a multi-layered coastal aquifer in southeast Australia to decades of groundwater pumping, and the groundwater age, flow paths and salinization processes were examined using isotopic tracers. Groundwater radiocarbon and tritium contents decline with distance and depth away from basin margins; however, in the main zone of pumping, radiocarbon activities are generally homogeneous within a given depth horizon. A lack of tritium and low radiocarbon activities (<25 pMC) in groundwater in and around the pumping areas indicate that seasonal recovery of water levels is related to capture of old water with low radioisotope activities, rather than arrival of recently recharged water. Mechanisms facilitating seasonal recovery include release of water from low-permeability layers and horizontal transfer of water from undeveloped parts of the basin. Overall stability in seasonally recovered water levels and salinities for the past three decades indicate that the system has reached a dynamic equilibrium with respect to water balance and salinity, following a major change in flow paths and solute distributions after initial development. Groundwater δ18O, δ2H and chloride contents indicate mixing between fresh meteoric-derived groundwater and marine water at the coast, with the most saline groundwater approximating an 80:20 mixture of fresh to oceanic water.  相似文献   

15.
The present study concerns the application of a numerical approach to describe the influence of anthropogenic modifications in surface flows (operation of a projected reservoir) on the freshwater-seawater relationships in a downstream coastal aquifer which has seasonal seawater intrusion problems (River Verde alluvial aquifer, Almuñécar, southern Spain). A steady-state finite element solution to the partial differential equation governing the regional motion of a phreatic surface and the resulting sharp interface between fresh water and salt water was used to predict the regional behavior of the River Verde aquifer under actual surface flow conditions. The present model approximates, with simple triangular elements, the regional behavior of a coastal aquifer under appropriate sinks, sources, Neumann and open boundary conditions. A steady-state solution to this numerical approach has been shown to precisely calculate freshwater heads, saltwater thicknesses, and freshwater discharges along steeply sloping coasts. Hence, the adequate treatment and interpretation of the hydrogeological data which are available for the River Verde aquifer have been of main concern in satisfactorily applying the proposed numerical model. Present simulated conditions consider steady-state yearly averaged amounts of external supplies of fresh water in order to determine the influences of the projected Otívar reservoir on the further behavior of the River Verde coastal aquifer. When recharges occur at the coastline, essentially because of freshwater deficits due to groundwater overexploitation, a hypothesis of mixing for the freshwater-saltwater transition zone is made in order to still allow the model to continue calculating groundwater heads under the sea level, and, as a consequence, the resulting seawater intrusion and recharges of saltwater from the sea. Simulations show that a considerable advance in seawater intrusion would be expected in the coastal aquifer if current rates of groundwater pumping continue and a significant part of the runoff from the River Verde is channeled from the Otívar reservoir for irrigation purposes.  相似文献   

16.
受气候变化和人类活动等因素的综合影响,地下水超采和含水层水量亏空已成为备受关注的全球性问题。为了弥补含水层水量亏空和促进地下水资源涵养,已探索出多种人为干预地下水补给的措施,其中通过河道开展地下水人工补给由于具有明显优势而受到重视。已有实践表明,受渗漏补给潜力和包气带调蓄能力等的限制,并不是所有河流或河段都适宜开展地下水人工补给工作。目前缺乏为大家广泛接受的适宜性评估方法。本研究以永定河生态补水为契机,以北京平原段河道和下伏含水层为研究区开展了案例研究,并用实测数据对研究结果进行了检验。应用指标体系法建立的适宜性评估模型（LMBGITSC模型）包括河床土地利用类型、河床介质类型、河床宽度、河床地形坡度、包气带介质类型、包气带厚度、包气带给水度、包气带水平渗透性等8个指标。案例研究结果表明,沿河流流向,通过河道渗漏补给地下水的适宜性由好变差（防渗河段除外）。该规律主要受渗漏补给潜力和包气带调蓄能力控制,因此适宜性也呈现出“阶梯式”演变规律。检验结果表明所建的评估方法适用性较好。该方法具有可移植性,因此也可为其他同类地区提供参考。  相似文献   

17.
Influence of flooding on groundwater flow in central Cambodia   总被引：2，自引：1，他引：1  
Cambodia is affected by flooding from the Mekong, Tonle Sap and Bassac rivers every year, which harms human populations and damages property, as well as alters the water quality in aquifer systems. The objective of this paper is to highlight the effects of river flooding on groundwater flow using numerical simulation. A two-dimensional groundwater flow model coupled with a groundwater recharge model was applied to the research area in central Cambodia. River level variation was included in model processes, and flood areas and periods were assigned. The results showed that during flooding periods, floodwater from the three rivers played an important role in recharging groundwater. During the dry season, Tonle Sap River received groundwater supply from the northwest, and levels in the Bassac and Mekong River dropped to lower than the groundwater level. This study improves understanding of the surface water and groundwater flow system in the study area.  相似文献   

18.
This paper uses Visual MODFLOW to simulate potential impacts of anthropogenic pumping and recharge variability on an alluvial aquifer in semi-arid northwestern Oklahoma. Groundwater withdrawal from the aquifer is projected to increase by more than 50% (relative to 1990) by the year 2050. In contrast, climate projections indicate declining regional precipitation over the next several decades, creating a potential problem of demand and supply. The following scenarios were simulated: (1) projected groundwater withdrawal, (2) a severe drought, (3) a prolonged wet period, and (4) a human adjustment scenario, which assumes future improvements in water conservation measures. Results indicate that the combined impacts of anthropogenic pumping and droughts would create drawdown of greater than 12 m in the aquifer. Spatially, however, areas of severe drawdown will be localized around large-capacity well clusters. The worst impacts of both pumping and droughts will be on stream–aquifer interaction. For example, the projected aquifer pumpage would lead to a total streamflow loss of 40%, creating losing stream system regionally. Similarly, a severe drought would lead to a total streamflow loss of >80%. A post-audit of the model was also carried out to evaluate model performance. By simulating various stress scenarios on the alluvial aquifer, this study provides important information for evaluating management options for alluvial aquifers.  相似文献   

19.
A FEFLOW three-dimensional (3D) groundwater model is developed to enhance the understanding of groundwater processes in the complex alluvial stratigraphy of Maules Creek Catchment (New South Wales, Australia). The aquifer vertical heterogeneity is replicated by indexing 204 lithological logs into units of high or low hydraulic conductivity, and by developing a 3D geological conceptual model with a vertical resolution based on the average lithological unit thickness for the region. The model mesh is populated with the indexed geology using nearest neighbour gridding. The calibrated model is successful in simulating the observed flow dynamics and in quantifying the important water-budget components. This indicates that the lateral groundwater flow from the mountainous region is the main inflow component of the system. Under natural conditions, the Namoi River acts as a sink of water, but groundwater abstraction increasingly removes a large amount of water each year causing dewatering of the system. The pumping condition affects the river–aquifer interaction by reversing the flow, from gaining to losing river conditions during the simulation period. The procedure is relevant for the development of groundwater models of heterogeneous systems in order to improve the understanding of the interplay between aquifer architecture and groundwater processes.  相似文献   

20.
Effective evaluation, management and abstraction of groundwater resources of any aquifer require accurate and reliable estimates of its hydraulic parameters. This study, therefore, looks at the determination of hydraulic parameters of an unconfined aquifer using both analytical and numerical approaches. A long-duration pumping test data obtained from an unconfined aquifer system within the Tailan River basin in Xinjiang Autonomous Region in the northwest of China is used, in this study, to investigate the best method for estimating the parameters of the aquifer. The pumping test was conducted by pumping from a radial collector well and measuring the response in nine observation wells; all the wells used in the test were partially penetrating. Using two well-known tools, namely AquiferTest and MODFLOW, as an aid for the analytical and numerical approaches, respectively, the parameters of the aquifer were determined and their outputs compared. The estimated horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield for the analytical approach are 38.1–50.30 m/day, 3.02–9.05 m/day and 0.204–0.339, respectively, while the corresponding numerical estimates are 20.50–35.24 m/day, 0.10–3.40 m/day, and 0.27–0.31, respectively. Comparing the two, the numerical estimates were found to be more representative of the aquifer in the study area since it simulated the groundwater flow conditions of the pumping test in the aquifer system better than the analytical solution.  相似文献   

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