Modeling Groundwater Flow and Seawater Intrusion in the Coastal Aquifer of Wadi Ham,UAE

Groundwater pumping from Kalbha and Fujairah coastal aquifer of the United Arab Emirates (UAE) has increased significantly during the last two decades to meet the agriculture water demands. Due to the lack of natural replenishment from rainfall and the excessive pumping, groundwater levels have declined significantly causing an intrusion of seawater in the coastal aquifer of Wadi Ham. As a result, many pumping wells in the coastal zone have been terminated and a number of farms have been abandoned. In this paper, MODFLOW was used to simulate the groundwater flow and assess the seawater intrusion in the coastal aquifer of Wadi Ham. The model was calibrated against a five-year dataset of historical groundwater levels and validated against another eleven-year dataset. The effects of pumping on groundwater levels and seawater intrusion were investigated. Results showed that reducing the pumping from Khalbha well field will help to reduce the seawater intrusion into the southeastern part of the aquifer. Under the current groundwater pumping rates, the seawater will continue to migrate inland.     

Simulation-Optimization Modeling for Sustainable Groundwater Development: A Moroccan Coastal Aquifer Case Study

A transient simulation model characterizing groundwater flow in the coastal aquifer of Rhis-Nekor was constructed and calibrated. The flow model was then used in conjunction with a genetic algorithm based optimization model to explore the optimal pumping schemes that meet current and future water demands while minimizing the risks for several adverse environmental impacts, such as saltwater intrusion prevention, avoiding excessive drawdown, as well as controlling waterlogging and salinity problems. Modeling results demonstrate the importance of this combined simulation-optimization methodology for solving groundwater management problems associated with the Rhis-Nekor plain.     

Upconing and Saline Water Intrusion and the Need for Water Conservation in the Lower Part of Wadi Fatimah,Western Saudi Arabia

Shallow aquifers were exploited in western Saudi Arabia a long time ago in history. In the last five decades, and under the conditions of an increasing supply of water, many new wells were drilled at relatively deeper intervals than the hand-dug wells of the time. In the downstream part of Wadi Fatimah, and over time, more saline water has been brought up in a number of wells. Overexploitation of groundwater for industrial and agricultural purposes has led to the appearance of two phenomena responsible for the salinization-upconing and saline water intrusion. Upconing occurs in separate pockets while saline water encroachment affects the lower part of Wadi Fatimah and the area towards the Red Sea coast. This article deals with the identification and delineation of areas affected by each of the two phenomena. The methodologies used in this work are mainly hydrogeological and hydrochemical. Resistivity surveys helped in delineating the fresh water-saline water interface. Methods to control upconing and saline water intrusion are suggested to safeguard the aquifer from further contamination. Effective conservation measures are recommended for the protection of groundwater resources in Wadi Fatimah.     

3D Variable Density Flow Simulation to Evaluate Pumping Schemes in Coastal Aquifers

A three dimensional model is presented for the simulation of seawater intrusion in coastal aquifers by considering the development of a transition zone and thus the variable density flow approach. The model is applied to a heterogeneous coastal aquifer to study the effects of the pumping rate, the salinity of freshwater inflow and the thickness of the aquifer, on the degradation of pumped water quality through wells in certain location. Even for an optimum pumping scheme solution based on a simple two-dimensional flow model, we simulate freshwater degradation in pumped water which depends on the salinity of freshwater inflow and aquifer thickness.     

Groundwater Flow Modeling of the Arlington Basin to Evaluate Management Strategies for Expansion of the Arlington Desalter Water Production

Water supply reliability in Southern California is facing serious problems because of reduction in the availability of water from the State Water Project and Colorado River, drought, and growing concerns about environmental restoration. Groundwater sources supply more than fifty-five percent of domestic demands in the Western Riverside County. Western Municipal Water District is planning to increase water supply reliability by expanding the Arlington Desalter production which requires additional groundwater pumping from the Arlington Basin. Western was concerned that increasing groundwater pumping will cause excessive decline in groundwater levels, leading to decreased yields at existing Desalter wells. Three-dimensional groundwater flow model was developed for the Arlington Basin to investigate different water management strategies. Five groundwater management scenarios were run for a 30-year time period. The five model runs were used to determine the feasibility of the Arlington aquifer system to supply groundwater to the Arlington Desalter over the 30-year life of the facility. Model simulation results showed that long-term groundwater pumping from the existing Desalter wells is not sustainable without artificial recharge. However two of the modeling scenarios which incorporated a combination of artificial recharge and new production wells, were shown to meet the increased Desalter yield requirements as well as minimize adverse impacts.     

Simulation-Optimization Modelling for Sustainable Groundwater Management in a Coastal Basin of Orissa, India

The Balasore coastal groundwater basin of Orissa in eastern India is under a serious threat of overdraft and seawater intrusion. Two optimization models were developed in this study for the efficient utilization of water resources in Balasore basin during non-monsoon periods: (a) a non-linear hydraulic management model for optimal pumpage, and (b) a linear optimization model for optimal cropping pattern in integration with a calibrated and validated groundwater flow simulation model. Based on the simulation-optimization modeling results, optimal pumping schedules, cropping patterns, and corresponding groundwater conditions are presented for three scenarios viz., wet, normal and dry years. It was found that optimal pumping schedules and corresponding cropping patterns differed significantly under the three scenarios, and the groundwater levels improved significantly under the optimal hydraulic conditions compared to the existing condition. In dry years, the groundwater levels under the present pumping pattern and the optimal pumpage indicated that the non-monsoon pumpage should not exceed the optimal pumpage in the absence of remedial measures in the basin. It is concluded that in order to ensure sustainable groundwater utilization in the basin, the optimal cropping pattern and pumping schedule should be adopted by the farmers.     

Regional management modeling of a complex groundwater system for land subsidence control

The three-dimensional groundwater flow model MODFLOW and the one-dimensional consolidation model are coupled and calibrated to simulate the piezometric levels and land subsidence in the complex multi-aquifer system of the lower Central Plain of Thailand. The mathematical models are calibrated against historical data for the period 1955–1990 by considerably updating the system conditions used by previous studies. The aquifer system responses to different pumping schemes are then predicted for the period 1991–2010. The modeling procedure is carried out in close consultation with the Department of Mineral Resources (DMR), Royal Thai Government. The conclusions of the study will allow the DMR to develop and implement updated groundwater management policies, land subsidence control strategies and action programs in the Bangkok Metropolitan Area.     

Alternatives to Reduce Pumping Effects in Glacial Stratified Drift Aquifers During Periods of Low Stream Flow

Low stream flows in the Fenton River, part of a hydrogeological setting characterized by glacial stratified drift, forces the University of Connecticut to frequently reduce groundwater withdrawals during the months of June–October. The objective of this study was to investigate stream/aquifer interactions in such a hydrogeologic system in order to increase water withdrawals while minimizing adverse impacts to in-stream flow. A groundwater flow model was developed using MODFLOW to investigate the influence of well location and pumping timing on in-stream flow in the vicinity of the water supply wells. The numerical model comprised detailed geophysical data and decadal hydrologic data (2000–2009) to assess well placement, rest periods and cyclical pumping. The relocation of a water supply well up to 228 m from the river had a positive but minimal improvement to stream flows (<2.83 L/s). When the well field was shut off for more than 45 days, stream flows returned to the no pumping condition with only slight impact at 30 days, whereas a 30 day rest period gave 4 weeks of dampened pumping influence on stream flows. A management scenario of 1 week cyclical pumping between two water supply wells following a 45 day rest period can allow for current restriction thresholds to be reduced by 28.3 L/s with minimal impact to stream flows (7.36 L/s) and would allow additional water to be pumped for all years in which there was a demand for water.     

Spatial Optimisation Technique for Planning Groundwater Supply Schemes in a Rapid Growing Urban Environment

Uneven distribution of domestic water in space and time is a major concern in many fast growing cities due to improper planning and lack of scientific approach. This problem is much severe where the maximum domestic water requirements are met from the groundwater resources. Optimising a single groundwater pumping scheme may be an easy task using simple linear programming technique but, if the number of pumping schemes and constraints are more, solutions for identifying such groundwater schemes are more difficult and laborious using conventional methods as the constraints varies in space and time. In this paper, a new technique was developed to identify new groundwater pumping schemes to meet the present and future domestic water requirements in space and time by integrating spatial optimisation technique with the groundwater model. The approach considers the possible optimum rate of groundwater pumping, minimising the cost of water supply scheme and having minimum impact on the downstream side groundwater table using high resolution satellite data (IKONOS), Geographical Information System (GIS) tools and optimisation techniques. Dehradun, which is one of the fast growing cities in India, was considered as a study area to demonstrate the proposed new technique. Domestic water demand for next two decades (up to 2,031) was forecasted and compared with the existing supplies. Nearly 48 additional groundwater pumping schemes were identified to cater the present and future demands. Its impact on the groundwater table was also studied using groundwater modelling technique.     

Optimal Locations of Groundwater Extractions in Coastal Aquifers

A regional water supply management model for coastal aquifers was developed. One of its outcomes is the definition of the optimized locations for groundwater withdrawal. Such a tool permits the analysis of alternative plans for groundwater extraction and the sustainable use of water resources in a coastal aquifer subject to saltwater intrusion. The principal components are the evolutionary optimization and the analytical/numerical simulation models. The optimization technique looks for the best well locations taking into consideration the economic results and the satisfaction of the societal water demand. However these two concerns are conditioned by trying to control the saltwater intrusion, i.e., preserving the environmental equilibrium. The simulation model uses the governing mathematical equations for groundwater movement to find the interface between freshwater and saltwater. Because of the non-linearity in the system and the possibility of a jumping interface, a security distance was defined. This is a controlling variable which can be set by the decision makers. The model was applied to a typical case with interesting results. For example, diagrams showing the relationship between the location of the wells and the security distance(s) are of importance to the managers. It was also crucial to have an understanding of the tradeoffs between groundwater withdrawals, positions of the wells from the coast line, and the security distance. The model was also applied to a real case in order to relate the extractions, distances and artificial recharge (not presented in this paper).     

松花江佳木斯市区段江水对地下水补给程度分析

采用MODFLOW软件,在佳木斯市区建立了地下水流模拟模型。在地下水开采井正常运行和全部关闭两种情况下,分别对现状年和设计典型年,运用所建模型求解松花江水对研究区地下水的补给量,分析补给程度,从一个侧面探讨江水污染对地下水水质的影响程度。计算结果表明:从求解的年内总量上,通过关闭开采井的方式能够抑制近1/4的江水侧渗补给;关闭开采井初期并不能迅速降低江水的侧渗补给量。     

Quantifying a Sustainable Management Space for Human Use of Coastal Groundwater under Multiple Change Pressures

In the densely populated coastal regions of the world, loss of groundwater due to seawater intrusion, driven by changes of climate, sea level, land use and water use, may critically impact many people. We analytically investigate and quantify the limits constraining a coastal aquifer’s sustainable management space, in order to avoid critical loss of the coastal groundwater resource by seawater intrusion. Limiting conditions occur when the intrusion toe reaches the pumping wells, well intrusion, or the marine-side groundwater divide, complete intrusion; in both cases the limits are functions of the seaward groundwater flow remaining after the human groundwater extractions. The study presents a screening-level approach to the quantification of the key natural and human-determined controls and sustainability limits for the human use of coastal groundwater. The physical and geometrical characteristics of the coastal aquifer along with the natural conditions for recharge and replenishment of the coastal groundwater are the key natural controls of the sustainable management space for the latter. The groundwater pumping rates and locations are the key human-determined controls of this space. The present approach to combining and accounting for both of these types of controls is simple, yet general. The approach is applicable across different scales and regions, and for historic, current and projected future conditions of changing hydro-climate, sea level, and human freshwater use. The use of this approach is also concretely demonstrated for the natural and human-determined controls and limits of the sustainable management space for two specific Mediterranean aquifers.     

Integration of Optimal Dynamic Control and Neural Network for Groundwater Quality Management

This study integrates an artificial neural network (ANN) and constrained differential dynamic programming (CDDP) to search for optimal solutions to a nonlinear time-varying groundwater remediation-planning problem. The proposed model (ANN-CDDP) determines optimal dynamic pumping schemes to minimize operating costs and meet water quality requirements. The model uses two embedded ANNs, including groundwater flow and contaminant transport models, as transition functions to predict groundwater levels and contaminant concentrations under time-varying pumping. Results demonstrate that ANN-CDDP is a simplified management model that requires considerably less computation time to solve a fine mesh problem. For example, the ANN-CDDP computing time for a case involving 364 nodes is 1/26.5 that of the conventional optimization model.     

Assessment of lake–groundwater interactions and anthropogenic stresses,using numerical groundwater flow model,for a Rift lake catchment in central Ethiopia

A steady-state groundwater flow model (MODFLOW) was used to study lake and groundwater interactions in a complex rift volcanic catchment. It also was used to assess the effects of water pumping from wells, and of variable recharge rates associated with climate and lake level changes, on the dynamics of the volcanic aquifers surrounding Lake Awassa. The model simulations were made after first developing a reasonable conceptual model, on the basis of conventional hydrogeological mapping, pumping test and hydrometeorological data analyses, and from ancillary information obtained from hydrochemical and isotope techniques. The model results indicated that the lakes and Rift aquifers are fed by large groundwater inputs that originate in the highlands. The lakes and rivers have important roles in recharging the aquifers in some locations. Lake Awassa receives a major groundwater inflow from its southern and eastern shorelines, while substantial water leakage from the lake occurs along the northern shoreline. The annual groundwater outflow from the catchment is estimated to 52.5 × 10⁶ m³. Scenario analyses revealed that increasing the current pumping rate from wells by fourfold will substantially reduce the groundwater level substantially, although the regional flow pattern would remain the same. There appears to be no immediate danger to the Rift aquatic environment from the current water pumping rate. Drying the small Lake Shalo and associated swamps, however, will cause a large change in the water balance of the larger Lake Awassa. Slight changes in groundwater recharge can cause large differences in groundwater levels for most of the Rift caldera floor far from the lake shores. This study provides a reasonable foundation for developing detailed transient predictive models, which can then readily be used as a decision support tool for development and implementation of sustainable water resources practices.     

Simulation Modeling for Efficient Groundwater Management in Balasore Coastal Basin,India

The Balasore coastal groundwater basin in Orissa, India is under a serious threat of overdraft and seawater intrusion. The overexploitation resulted in abandoning many shallow tubewells in the basin. The main intent of this study is the development of a 2-D groundwater flow and transport model of the basin using the Visual MODFLOW package for analyzing the aquifer response to various pumping strategies. The simulation model was calibrated and validated satisfactorily. Using the validated model, the groundwater response to five pumping scenarios under existing cropping conditions was simulated. The results of the sensitivity analysis indicated that the Balasore aquifer system is more susceptible to the river seepage, recharge from rainfall and interflow than the horizontal and vertical hydraulic conductivities and specific storage. Finally, based on the modeling results, salient management strategies are suggested for the long-term sustainability of vital groundwater resources of the Balasore groundwater basin. The most promising management strategy for the Balasore basin could be: a reduction in the pumpage from the second aquifer by 50% in the downstream region and an increase in the pumpage to 150% from the first and second aquifer at potential locations.     

Application of the high performance computing techniques of parflow simulator to model groundwater flow at Azraq basin

Being one of the largest groundwater basins in Jordan, the Azraq basin is considered to be an important domestic and agricultural water source. Lately, there have been growing concerns about the continuous depletion and deterioration in groundwater quality in the basin due to intensive pumping beyond the safe yield of the basin. This is where assessment studies equipped with the proper modeling tools come into the picture. The highly advanced groundwater model, ParFlow, was utilized in this project in order to model groundwater flow in the basin. ParFlow employs the latest numerical techniques along with the massive power of parallel computing to utilize three-dimensional heterogeneity in groundwater flow modeling. This was tested against the homogeneous assumptions employed in more commonly used models such as Processing Modflow. Modeling results were compared to those produced by the PM5 modeling studies conducted by relevant official agencies in Jordan. Furthermore, the calibrated flow model was used to predict the aquifer system's response to a pumpage scheme of 55.5 MCM/year. The results showed that the maximum drawdown predicted by ParFlow was greater than the amount predicted by Modflow for the same pumping scheme. One of the causes of this difference in predictions may be attributed to the fact that ParFlow gives a general, more comprehensive picture of the system at hand, as opposed to the point dependent results obtained via Modflow.     

陕西省吴堡县岔上水源地地下水允许开采量评价

根据陕西省吴堡县岔上水源地水文地质条件,确定了研究范围和边界条件,建立了研究区水文地质概念模型和地下水二维非稳定流数学模型,利用基于有限差分法的Visual MODFLOW进行地下水流数值模拟计算。经过模型的识别和验证,获取可靠的水文地质参数,然后对水源地地下水资源进行定量评价。通过对比设计了9种开采方案,选取了最为合理的开采方案,最终得到岔上水源地平枯期允许开采量均为6 880m3/d。根据模型预报结果,水源地目前的设计开采量是可行的。研究结果为研究区地下水资源的合理开发利用提供了依据。     

Distributed Simulation‐optimization Model for Conjunctive Use of Groundwater and Surface Water Under Environmental and Sustainability Restrictions

Evolving optimal management strategies are essential for the sustainable development of water resources. A coupled simulation-optimization model that links the simulation and optimization models internally through a response matrix approach is developed for the conjunctive use of groundwater and surface water in meeting irrigation water demand and municipal water supply, while ensuring groundwater sustainability and maintaining environmental flow in river. It incorporates the stream-aquifer interactions, and the aquifer response matrix is generated from a numerical groundwater model. The optimization model is solved by using MATLAB. The developed model has been applied to the Hormat-Golina valley alluvial stream-aquifer system, Ethiopia, and the optimal pumping schedules were obtained for the existing 43 wells under two different scenarios representing with and without restrictions on stream flow depletion, and satisfying the physical, operational and managerial constraints arising due to hydrological configuration, sustainability and ecological services. The study reveals that the total annual optimal pumping is reduced by 19.75?% due to restrictions on stream flow depletion. It is observed that the groundwater pumping from the aquifer has a significant effect on the stream flow depletion and the optimal conjunctive water use plays a great role in preventing groundwater depletion caused by the extensive pumping for various purposes. The groundwater contribution in optimal conjunctive water use is very high having a value of 92?% because of limited capacity of canal. The findings would be useful to the planners and decision makers for ensuring long-term water sustainability.

     

三峡与南水北调工程对长江口水源地的影响

利用Delft3D-Flow建立了长江口二维潮流和盐度数学模型,并利用现场实测的水流、盐度数据对模型进行率定验证,较好地模拟了长江口盐水入侵的周期性变化规律.在此基础上,分别将枯水期三峡工程和南水北调工程各调水方案与外海的典型潮波进行组合模拟多种水文条件下的盐度场,并对宝钢水库、陈行水库以及在建的青草沙水库的取水口盐度进行了分析.结果表明:南水北调东线工程的预期最大调水量为1000 m3/s的调水方案将加剧长江口的盐水入侵,水库取水口附近的盐度变大;三峡工程枯水期下泄流量增加,有利于缓解长江口水源地的盐水入侵.     

A Cost-Effective Method to Control Seawater Intrusion in Coastal Aquifers

Intrusion of seawater into coastal aquifers is considered one of the most important processes that degrade water-quality by raising the salinity to levels exceeding acceptable drinking standards. Therefore saltwater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents a cost-effective method to control seawater intrusion in coastal aquifers. This methodology ADR (Abstraction, Desalination and Recharge) includes; abstraction of saline water and recharge to the aquifer after desalination. A coupled transient density-dependent finite element model is developed for simulation of fluid flow and solute transport and used to simulate seawater intrusion. The simulation model has been integrated with an optimization model to examine three scenarios to control seawater intrusion including; abstraction, recharge and a combination system, ADR. The main objectives of the models are to determine the optimal depths, locations and abstraction/recharge rates for the wells to minimize the total costs for construction and operation as well as salt concentrations in the aquifer. A comparison between the combined system (ADR) and the individual abstraction or recharge system is made in terms of total cost and total salt concentration in the aquifer and the amount of repulsion of seawater achieved. The results show that the proposed ADR system performs significantly better than using abstraction or recharge wells alone as it gives the least cost and least salt concentration in the aquifer. ADR is considered an effective tool to control seawater intrusion and can be applied in areas where there is a risk of seawater intrusion.