Finite-difference Ground-water Flow Model Research Articles

Simulation of coupled groundwater flow and contaminant transport using quintic B-spline collocation method

PurposeThe purpose of this study is to introduce a new numerical scheme with no stability condition and high-order accuracy for the solution of two-dimensional coupled groundwater flow and transport simulation problems with regular and irregular geometries and compare the results with widely acceptable programs such as Modular Three-Dimensional Finite-Difference Ground-Water Flow Model (MODFLOW) and Modular Three-Dimensional Multispecies Transport Model (MT3DMS).Design/methodology/approachThe newly proposed numerical scheme is based on the method of lines (MOL) approach and uses high-order approximations both in space and time. Quintic B-spline (QBS) functions are used in space to transform partial differential equations, representing the relevant physical phenomena in the system of ordinary differential equations. Then this system is solved with the DOPRI5 algorithm that requires no stability condition. The obtained results are compared with the results of the MODFLOW and MT3DMS programs to verify the accuracy of the proposed scheme.FindingsThe results indicate that the proposed numerical scheme can successfully simulate the two-dimensional coupled groundwater flow and transport problems with complex geometry and parameter structures. All the results are in good agreement with the reference solutions.Originality/valueTo the best of the authors' knowledge, the QBS-DOPRI5 method is used for the first time for solving two-dimensional coupled groundwater flow and transport problems with complex geometries and can be extended to high-dimensional problems. In the future, considering the success of the proposed numerical scheme, it can be used successfully for the identification of groundwater contaminant source characteristics.

Estimating natural groundwater recharge taking into consideration temporal and spatial variability for arid unconfined aquifer

ABSTRACT Water scarcity is one of the major critical affecting arid climate countries. In addition, population growth and climate change are threatening the sustainable development of water resources in the upcoming decades. Therefore, managing groundwater can solve water scarcity such that sustainable development is ensured for future generations. Hence, it is crucial to assess the current quantity of groundwater by analyzing groundwater variables. Thus, natural groundwater recharge could be utilized as an indicator to assess groundwater quantity conditions. This study aims to estimate natural groundwater recharge in an arid unconfined aquifer. El-Qaa plain in Sinai, Egypt was chosen as a case study. Recharge was estimated taking into consideration spatial and temporal variability. To accomplish this, the WetSpass (Water and Energy Transfer between Soil, Plants, and Atmosphere under quasi-Steady State) model was applied. The model was run using morphological, landuse – land cover and climate data from 1986 to 2015 with a monthly time step. To calibrate the model, the isotope signature of δ18O and δ2 H of water was analyzed to determine the natural groundwater recharge of the aquifer. The obtained recharge value was utilized as a reference value for the calibration process. The results were validated using a finite-difference groundwater flow model (MODFLOW). The recharge values were imported to MODFLOW followed via a transient run from 2000 to 2011. The validation was conducted by comparing the simulated groundwater level with the observed ones. After validation process, the inter-annual and seasonal variability of recharge were determined, and a relationship between recharge and other hydrological parameters was deduced. In addition, the recharge distribution was mapped to depict the recharge spatial variability. The results show that the current recharge rate ranges from approximately 8.10 to 16.62 mm/yr, with a mean annual recharge rate of nearly 12.36 mm/yr. The study might be useful for hydrogeologists for determining potential recharge in the study area, groundwater modelers for developing a reliable groundwater flow model, and decision-makers for planning appropriate future sustainable development through water resources management.

River Bank Filtration Process Using Groundwater Flow Modeling and Particle Tracking Approach in a Saline Coastal Aquifer

River bank filtration (RBF), as one of the sustainable natural treatment techniques, can provide risk-free drinking water supply to rural villages where piped water supply through conventional treatment schemes is very expensive. The main purpose of this paper is to report the results of a RBF production well implemented in a complex hydrogeological setting under the ephemeral Varaha river influenced by the saline coastal aquifer in the Visakhapatnam district of Andhra Pradesh (India) for the supply of drinking water to the nearby rural habitats that have no organized water supply. To understand and identify the hydraulics of the river–aquifer exchanged water, particle tracking analysis to determine the travel times of river water path lines, capture zones, the proportion of bank filtrate and river water, and groundwater into RBF production well consequent to pumping were carried out using modular finite difference groundwater flow model (MODFLOW) in conjunction with a particle-tracking model for MODFLOW (MODPATH). The river–aquifer and well field interaction were studied by developing a two-dimensional two-layer groundwater flow model with a partially penetrating well in an unconfined aquifer. The flow modeling simulation results together with MODPATH particle tracking analyses revealed that the installed RBF production well could yield about 61% river water through bank filtration and the remainder from the groundwater. The flow model was also used to optimize the pumping duration from the RBF production well without compromising the water quality of the bank filtrate water. The optimum pumping duration was estimated to be 5 h a day at the rate of 31.2 m3/h from continuous pumping during the monsoon period. The performance and quality of the bank filtrate from the well demonstrated that the RBF technique could also be a potential and viable approach for the supply of safe drinking water from an ephemeral river-induced bank filtrate influenced by the saline coastal aquifer.

An Investigation of Recharging Groundwater Levels through River Ponding: New Strategy for Water Management in Sutlej River

Groundwater is an essential water resource in the current era, and studying its sustainability and management is highly necessary nowadays. In the current area of research interest, the reduced mean annual Sutlej River flow, the increase in the population/built-up areas, and enhanced groundwater abstractions have reduced groundwater recharge. To address this issue, groundwater recharge modeling through ponding of the Sutlej River was carried out using a modular three-dimensional finite-difference groundwater flow model (MODFLOW) in a 400 km2 area adjacent to Sutlej River. The mean historical water table decline rate in the study area is 139 mm/year. The population and urbanization rates have increased by 2.23 and 1.62% per year in the last 8 years. Domestic and agricultural groundwater abstraction are increasing by 1.15–1.30% per year. Abstraction from wells and recharge from the river, the Fordwah Canal, and rainfall were modeled in MODFLOW, which was calibrated and validated using observed data for 3 years. The model results show that the study area’s average water table depletion rate will be 201 mm/year for 20 years. The model was re-run for this scenario, providing river ponding levels of 148–151 m. The model results depict that the water table adjacent to the river will rise by 3–5 m, and average water table depletion is expected to be reduced to 151 to 95 mm/year. The model results reveal that for ponding levels of 148–151 m, storage capacity varies from 26.5–153 Mm3, contributing a recharge of 7.91–12.50 million gallons per day (MGD), and benefiting a 27,650–32,100-acre area; this means that for areas benefitted by dam recharge, the groundwater abstraction rate will remain sustainable for more than 50 years, and for the overall study area, it will remain sustainable for 7–12.3 years. Considering the current water balance, a recharging mechanism, i.e., ponding in the river through the dam, is recommended for sustainable groundwater abstraction.

高寒内陆河流域植被覆盖增加对地下水补给的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 高寒内陆河流域植被覆盖增加对地下水补给的影响 DOI: 10.5846/stxb202207212098 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（42161020）；青海省科技厅应用基础研究项目（2021-ZJ-705） Impacts of the increasing vegetation coverage on groundwater recharge in an alpine and arid endorheic river watershed Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:地下水是干旱区内陆河流域的主要基础性资源，对流域生态安全、可持续发展等具有重要意义。干旱/半干旱区的地下水补给比湿润地区更易受到地表覆盖条件的影响。为揭示干旱区内陆河流域植被覆盖增加对地下水补给的影响，以巴音河中下游为例，针对土壤和水评价工具（SWAT）模型未有效考虑降水、地形等因素对植被覆盖影响的缺陷，改进SWAT模型，采用全球地表卫星叶面积指数（GLASS LAI）数据代替其LAI计算模块，再结合SWAT土地利用更新模块，准确刻画区域植被覆盖变化。将改进后的SWAT模型与模块化有限拆分地下水流耦合（MODFLOW）模型耦合，准确模拟并分析植被覆盖增加对流域地下水补给的影响。结果表明：基于植被动态变化的土壤和水评价工具与模块化有限拆分地下水流耦合模型（DVSWAT-MODFLOW）模型的月蒸散发及月地下水位模拟效果较好；巴音河中下游2019年林地及草地面积以及LAI较2001年明显增加；2019年植被覆盖情况对应的年际及月际尺度地下水补给量较2001年分别减少了6.1-26.52 mm以及0-15.03 mm；植被覆盖增加对年际尺度地下水补给量的影响强弱在一定程度上取决于年降水量，对月际尺度地下水补给量影响较强的月份集中于植物生长旺盛且降水较多时期。 Abstract:The groundwater is one of the most important basic resources in arid land. The groundwater recharge is easier to be affected by vegetation coverage in the arid and semi-arid areas than the wet areas. Bayin River Basin, a typical alpine and arid endorheic river watershed is located in the northeast of the Qaidam Basin. In the past 20 years, because of the warmer and more humid climate and human activities, the vegetation coverage condition of the watershed was becoming better. Calculation of the groundwater recharge in endorheic watershed is difficult. Soil and Water Assessment Tool (SWAT) is one of the most important tools that can simulate the watershed hydrological processes and its impact factors. However, it has considerable limitations in vegetation coverage and groundwater processes simulation. For the vegetation coverage simulation (leaf area index, LAI), it neglects the precipitation and terrain, which is important in arid land; For the groundwater simulation, it only is based on a simple linear mathematical formula without consideration of the physical processes. To better reveal the impacts of the vegetation coverage increasing on groundwater recharge in arid inland river, this research modified the SWAT model by replacing the LAI module with Global Land Surface Satellite (GLASS) based on LAI. The land use/cover change of the Middle and Lower Reaches of the Bayin River was further considered to better simulate the vegetation dynamics. After that, the modified SWAT model (named Dynamic Vegetation SWAT, DVSWAT) was coupled with the MODFLOW (MODular finite difference groundwater FLOW model), a professional groundwater processes simulation model. The latest GLEAM (Global Land Evaporation Amsterdam Model) v3 based on monthly evapotranspiration data and the observed groundwater level data were used to calibrate the DVSWAT-MODFLOW. We further used the variable-controlling approach to analyze the impacts of the vegetation coverage increasing on groundwater recharge based on the simulation results of the calibrated DVSWAT-MODFLOW. The results showed that the performance of the DVSWAT-MODFLOW in modelling the monthly evapotranspiration was good, with the R2 value of over 0.83, NSE value of over 0.68, and PBIAS value within -22%-22% for each subbasin. The performance of the DVSWAT-MODFLOW in modelling the monthly groundwater level was good as well, with the R2 value of over 0.95 and absolute bias of below 1 m for each groundwater level observation well. The area of the forest land and grassland in the study area increased 5.41 times and 98.96%, respectively, in 2019 compared to 2001. In addition, the annually average LAI of the study in 2019 increased 28.83% than 2001. The yearly and monthly groundwater recharge reduced about 6.1-26.52 mm and 0-15.03 mm, respectively, under the impacts of the increased vegetation coverage. The influence of the increasing vegetation coverage on the annual groundwater recharge depends on the annual precipitation to a certain extent. The months with strong influence on the monthly groundwater recharge are concentrated in the period of vigorous plant growth and more precipitation. 参考文献 相似文献 引证文献

Specifying the hydrogeological parameters range for a groundwater flow model in El-Qaa Plain aquifer, Sinai, Egypt

Hydrogeological parameters are very uncertain to specify in the groundwater flow models. Hence, it is important to specify a range for these parameters to be further utilized by the groundwater model users. In El-Qaa Plain, previous researchers have determined the hydrogeological parameters such as transmissivity, hydraulic conductivity, and mean annual recharge rate using geophysical methods, pumping tests, hydrological models, and groundwater flow models. However, they are also limited to specific locations and do not spatially distribute. In this paper, an effort has been accomplished to specify a specific range for the aquifer hydrogeological parameters using inverse groundwater modeling taking into account the spatial heterogeneity. These ranges could be taken into consideration during modeling groundwater flow. Hence, a finite-difference groundwater flow model has been applied using the ModFLOW model. Regularized pilot points method (RPPM) has been chosen as an inverse modeling technique to specify the accurate values of the aquifer parameters. Model-independent parameter estimation and uncertainty analysis (PEST) has been utilized to estimate the parameters. The results show that the geometric mean of the hydraulic conductivity in the study area ranges from proximity 1 to 2 m/day. Additionally, the geometric mean of the transmissivity ranges from nearly 200 to 500 m2/day. A relationship between the mean annual recharge rate and hydrogeological parameters has been determined. Besides, maps have been generated showing the spatial heterogeneity of the hydraulic conductivity. These maps could be further utilized by groundwater flow modelers to predict the potential of groundwater flow and pollution in the future.

Analysis of Water Supply Capacity of a Sand Dam

A sand dam is an old technology used to trap sand materials and store water in dry riverbeds. Besides the volume of sand stored, the water storage and supply capacity of the sand dam depends principally on material properties including hydraulic conductivity (K) and the specific yield (Sy). In this study, the water supply capacity of a sand dam, applied in South Korea with a modified scheme, was analyzed. Imported sand materials were placed in three layers, and perforated drain pipes were installed to abstract the water to a collection tank. Using a Modular Finite-Difference Groundwater Flow (MODFLOW) model, the drain pipe discharge related to aquifer properties and supply capacity of a sand dam was evaluated. Using the model, the productivity of the sand storage with several cases of inflow conditions was assessed. For the period from 9 March 2020 to 16 May 2022, the results of calculation of water supply for the installation and operation of new sand dam are as follows. Regarding the actual inflow condition, compared to the average water supply of the existing water intake source, the sand dam installation increased water supply by 61.6%, and the sand dam installation showed an effect of improving the water supply by 36.0% for the minimum water supply. The calculated water supply for the condition where the inflow was reduced by 50% showed an effect of improving water supply by over 70% on average due to the installation of the sand dam. The findings would be a benchmark for future expansions of the scheme in related places, and management and maintenance of the system.

A Dynamic Modeling Approach to Predict Water Inflow during Karst Tunnel Excavation

During tunnel construction in strongly developed karst terrain, water inrush hazards often occur due to the complex hydrogeological conditions, which require accurate prediction of water inflow. In this study, a dynamic modeling approach for water inflow prediction of karst tunnels using the conduit flow process (CFP) is developed that considers both karst duality and changing boundary conditions of the tunnel. The CFP model has a good agreement with field-observed hydraulic head after calibration, and the Nash–Sutcliffe model efficiency (NSE) for the CFP model is 97.3%. Numerical calculation of water inflow was conducted in a successive drilling scenario with permeability change of the surrounding rocks. Additionally, a modular three-dimensional finite-difference ground-water flow model (MODFLOW) has been applied to predict the water inflow, for comparison with the CFP model. The prediction results obtained from the CFP model are generally in close agreement with the field-observed results; the percentage errors were 13.3% and 5.4%, respectively. For the MODFLOW model, the percentage errors were 34.2% and 36.8%, respectively. The proposed CFP model is both closer to reality and more reasonable than the MODFLOW model in predictive analysis of water inflow into karst tunnels, reflecting the influence of karst conduits on the water inflow process.

Identification and Prediction of Crop Waterlogging Risk Areas under the Impact of Climate Change

Waterlogging refers to the damage to plants by water stress due to excess soil water in the crop’s root zone that exceeds the maximum water holding capacity of the field. It is one of the major disasters affecting agricultural production. This study aims to add a crop waterlogging identification module to the coupled SWAT (Soil and Water Assessment Tools)-MODFLOW (Modular Finite Difference Groundwater Flow Model) model and to accurately identify and predict crop waterlogging risk areas under the CMIP6 (Coupled Model Intercomparison Project 6) climate scenarios. The result showed that: (1) The SWAT-MODFLOW model, which coupled with a crop waterlogging identification module, had good simulation results for LAI (Leaf Area Index), ET (Evapotranspiration), spring wheat yield, and groundwater level in the middle and lower reaches of the Bayin River; (2) The precipitation showed an overall increasing trend in the Bayin River watersheds over the next 80 years under the SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios. The temperature showed a clear increasing trend over the next 80 years under the SSP2-4.5 and SSP5-8.5 scenarios; (3) Under the SSP1-2.6 scenario, the mountain runoff from the upper reaches of the Bayin River was substantially higher than in other scenarios after 2041. The mountain runoff in the next 80 years will decrease substantially under the SSP2-4.5 scenario. The mountain runoff over the next 80 years showed an initial decrease and then an increasing trend under the SSP5-8.5 scenario; (4) During the historical period, the crop waterlogging risk area was 10.9 km2. In the next 80 years, the maximum crop waterlogging area will occur in 2055 under the SSP1-2.6 scenario. The minimum crop waterlogging area, 9.49 km2, occurred in 2042 under the SSP2-4.5 scenario. The changes in the area at risk of crop waterlogging under each scenario are mainly influenced by the mountain runoff from the upper reaches of the Bayin River.

Flood Control and Aquifer Recharge Effects of Sponge City: A Case Study in North China

Sponge City is an integrated urban stormwater management approach and practice to tackle waterlogging, flooding, water scarcity, and their related problems. Despite many positive effects of Sponge City on flood control that have been investigated and revealed, the effect on aquifer recharge is still less known. Considering maximizing the function of natural elements such as surface water bodies and subsurface storage space, to minimize the use of a gray drainage system, a Sponge City design was proposed to substitute the planning development scheme in the study area. The stormwater management model of SWMM (storm water management model) and the groundwater flow model of MODFlow (Modular Three-dimensional Finite-difference Groundwater Flow Model) were adopted to evaluate the flood-control effect and aquifer-recharge effect, respectively. Compared with the traditional planning scenario, the peak runoff is approximately 92% less than that under the traditional planning scenario under the condition of a 5-year return period. Due to the increase in impervious areas of urban construction, the total aquifer recharge from precipitation and surface water bodies was decreased both in the present planning scenario and the Sponge City design scenario. However, the Sponge City design has a positive impact on maintaining groundwater level stabilization and even raises the groundwater level in some specific areas where stormwater seepage infrastructure is located.

Evaluating the Impacts of Pumping on Aquifer Depletion in Arid Regions Using MODFLOW, ANFIS and ANN

In arid regions, the groundwater drawdown consistently increases, and even for a constant pumping rate, long-term predictions remain a challenge. The present research applies the modular three-dimensional finite-difference groundwater flow (MODFLOW) model to a unique aquifer facing challenges of undefined boundary conditions. Artificial neural networks (ANN) and adaptive neuro fuzzy inference systems (ANFIS) have also been investigated for predicting groundwater levels in the aquifer. A framework is developed for evaluating the impact of various scenarios of groundwater pumping on aquifer depletion. A new code in MATLAB was written for predictions of aquifer depletion using ANN/ANFIS. The geotechnical, meteorological, and hydrological data, including discharge and groundwater levels from 1980 to 2018 for wells in Qassim, were collected from the ministry concerned. The Nash–Sutcliffe efficiency and mean square error examined the performance of the models. The study found that the existing pumping rates can result in an alarming drawdown of 105 m in the next 50 years. Appropriate water conservation strategies for maintaining the existing pumping rate can reduce the impact on aquifer depletion by 33%.

A NUMERICAL GROUNDWATER FLOW MODEL OF WADI SAMAIL CATCHMENT USING MODFLOW SOFTWARE

The climate in most of Gulf Cooperation Council (GCC) countries is considered arid with limited water resources. Proper management of scarce water resources is therefore necessary for sustainable water supply while meeting the growing water demands. A three-dimensional finite-difference groundwater flow model of Wadi Samail Catchment was developed to simulate groundwater flow and to evaluate the sensitivity of the model to the varying of input parameters. Model inputs include lithology of the aquifer derived from borehole data, observed groundwater levels, rainfall, and initial hydraulic conductivity values from pumping tests. The aquifer was divided into four layers. The steady-state calibration was carried out using data in 14 monitoring wells in July 2016. The hydraulic conductivity (k) and recharge values were calibrated using observed groundwater levels with the estimated root mean squared error (RMSE) of 0.8m. The estimated parameters were verified with groundwater levels in October 2016. The RMSE between observed and simulated water levels was 0.81m. The calibrated model was then used to assess the sensitivity of the model to the changes in pumping rate, hydraulic conductivity (k), and recharge. Results showed that the water levels were most sensitive to the changes in hydraulic conductivity of the first layer. While pumping rates and recharge were less sensitive compared to the hydraulic conductivity. In conclusion, the sensitivity analysis results can be used as a management tool for sustainable water resources.

Climate change scenarios and its effect on groundwater level in the Hiranyakeshi watershed

The availability of groundwater resources is depleting due to growth of population, urbanization, industrialization and climate change. With increasing concern on global climate change all over the world, there has been raising interest on water resource conservation. Similarly, Hukkeri (lies within Hiranyakeshi watershed) is one such town under Belagavi, Karnataka is facing severe groundwater problems from the past few years due to uneven rainfall, climate change and over exploitation of groundwater for irrigation activities. This study focused to measure and evaluate groundwater resources by modelling approach for the Hiranyakeshi watershed using Visual MODFLOW Flex software (Modular Finite Difference Groundwater Flow Model). The model calibration achieved by Parameter Estimation (PEST), and the model performance was checked by using coefficients R2, RMSE and NRMSE. It is observed that the coefficients of R2, RMSE and NRMSE obtained are 0.98, 1.68 and 3.41% respectively. The results from the model simulation gives increase in head of 1.8 m during 5years simulation period. The model was again simulated for the A1B climate change scenarios for the period 2021–2050 using Hadley Regional Model 3 (HadRM3) data for the Hiranyakeshi watershed to measure the effects of climate change on the groundwater recharge. Based on the long term output analysis, it is expected that there is an increase in the average annual temperature by 2.59 °C, precipitation by 81.50% and groundwater recharge by 24.91%.

Modeling groundwater flow and seawater intrusion in the Terkos Lake aquifer due to Canal Istanbul excavation

A navigational canal is planned to be constructed to link the Black Sea with the Marmara Sea in Istanbul, Turkey. This canal will be built beside an important freshwater lake, with a minimum distance of 1.0 km between them. This lake is an essential source of freshwater for the city of Istanbul. To evaluate the effects of canal construction on the freshwater aquifer between the lake and the canal, a 2D finite difference groundwater flow and solute transport model were developed to quantify the possible seepage flow and to simulate the spatial variations of the salinity distribution in the coastal aquifer, taking into consideration the transition zone between the freshwater and seawater bodies. The numerical model was calibrated by the average hydrologic conditions of 18 years of well records. Arc GIS was used to prepare the spatial datasets for the conceptual model in MODFLOW. The results indicated that, after canal implementation and the attaining of a steady state, 25% of the annual available water in the lake will be drained to the canal in terms of seepage. It was also found that the length of the seawater intrusion in the aquifer is strongly related to the hydraulic gradients, when the lake water level declines for 1 m above the mean sea level, for example, the length of the saltwater extends to halfway between Terkos Lake and Canal Istanbul.

Determining hydrogeological parameters of an aquifer in Sirjan Basin using Envisat ASAR interferometry and groundwater modelling

ABSTRACT Excessive groundwater exploitation in Sirjan plain, located in south of Iran, has caused severe land subsidence. The main purpose of this paper is to determine the hydrogeological parameters of the aquifer system in Sirjan plain. To this end, the groundwater flow was simulated in both steady and transient states using the United States Geological Survey Modular Three-Dimensional Finite-Difference Groundwater Flow Model, MODFLOW. The hydraulic conductivity parameter of the aquifer system was first estimated and calibrated in the steady state by simulating the hydraulic head at 63 piezometric wells. The specific yield and recharge parameters were then calibrated in the transient state by simulating the drawdown within a period of interest, i.e. 23 September 2004 to 22 September 2005. The main innovation of this paper, however, is to use the potential of Synthetic Aperture Radar (SAR) interferometry time-series analysis in the last step of the proposed algorithm. Small Baseline Subset (SBAS) time-series analysis was applied using Envisat Advanced SAR (ASAR) images acquired from 1 June 2004 to 28 September 2010. The merit of SBAS time series is that it enables us to calculate the amount of subsidence in each period of interest while minimizing the temporal decorrelation effect. In the last step, the SBAS time-series analysis results were obtained to extract the accumulated subsidence from 19 October 2004 to 30 August 2005. The aquifer compaction due to this period was calculated in the Interbed Storage Package (IBS1) for MODFLOW in order to calibrate storage coefficient in a trial-and-error manner so as the calculated subsidence and the observed one by SAR interferometry be in a good agreement. The Root Mean Square Error (RMSE) between the simulated subsidence and the observed one is calculated as 0.019 m which is an indication of the high performance of modelling.

Providing decision support system in groundwater resources management for the purpose of sustainable development

Decision support system (DSS) for sustainable development is an efficient tool in managing aquifers, since an aquifer as a complex system is not a structural issue due to varied components. In this article, software entitled DSS-SMGW-01 is developed based on the so-called DSS to realize sustainable management of groundwater. This system includes a database, a simulation model, and a decision-making model controlled through a graphical user interface. This software controls exploitation of groundwater in managing subunits and integrated management of water resources and consumptions. Furthermore, management options are evaluated by the software according to aquifer sustainability and socio-economic indicators. In this system, WEAP-MODFLOW linked model (Water Evaluation And Planning system dynamically linked to the United States Geological Survey modular finite-difference groundwater flow model), Analytic Hierarchy method, and Simple Additive Weighting method are utilized for simulation of groundwater resources system, weighting indicators and prioritizing options, respectively. In order to evaluate efficiency of the exerted system, Qazvin plain data was used and 68 experts from different parts of water industry in Iran were consulted to have the best analysis on weighting the indicators. Consequently, the prepared system was found to be successful in designing and prioritizing the seven managing indices.

Predicting the impacts of climate change on groundwater recharge in an arid environment using modeling approach

PurposeGroundwater is an important source of water supply in arid and semi-arid areas. The purpose of this study is to predict the impact of climate change on groundwater recharge in an arid environment in Ilam Province, west of Iran.Design/methodology/approachA three-dimensional transient groundwater flow model (modular finite difference groundwater FLOW model: MODFLOW) was used to simulate the impacts of three climate scenarios (i.e. an average of a long-term rainfall, predicted rainfall in 2015-2030 and three years moving average rainfall) on groundwater recharge and groundwater levels. Various climate scenarios in Long Ashton Research Station Weather Generator were applied to predict weather data.FindingsHadCM3 climatic model and A2 emission scenario were selected as the best methods for weather data generation. Based on the results of these models, annual precipitation will decrease by 3 per cent during 2015-2030. For three emission scenarios, i.e. an average of a long-term rainfall, predicted rainfall in 2015-2030 and three years moving average rainfall, precipitation in 2030 is estimated to be 265, 257 and 247 mm, respectively. For the studied aquifer, predicted recharge will decrease compared to recharge calculated based on the average of long-term rainfall.Originality/valueThe decline of groundwater level in the study area was 11.45 m during the past 24 years or 0.48 m/year. Annual groundwater depletion should increase to 0.75 m in the coming 16 years via climate change. Climate change adaptation policies in the basin should include changing the crop type, as well as water productivity and irrigation efficiency enhancement at the farm and regional scales.

Groundwater Modeling Under Variable Operating Conditions Using SWAT, MODFLOW and MT3DMS: a Catchment Scale Approach to Water Resources Management

This paper presents an integrated modeling approach by linking soil and water application tool (SWAT), modular finite difference groundwater flow (MODFLOW) and modular 3-dimensional multi-species transport (MT3DMS) models capable of predicting a groundwater system response, in terms of flow and salt concentrations, to current and future development conditions. SWAT, a semi-distributed hydrologic model, estimates the spatio-temporal distribution of groundwater recharge rates. These rates are then input to MODFLOW using an interface module developed that maps the HRU-based spatial resolution of SWAT outflows into the cell-based spatial structure of inputs to MODFLOW and MT3DMS. The integrated SWAT-MODFLOW-MT3DMS model is used in modeling Dehloran aquifer system located in the arid western region of Iran, experiencing changes in land-use, irrigation system and pumping locations and loads. The results illustrate the significance of the developed integrated modeling tool in quantifying the impact of changes in land and surface water resources on its subsurface water system.

Stochastic groundwater modeling of a sedimentary aquifer: evaluation of the impacts of abstraction scenarios under conditions of reduced recharge

A transient finite difference groundwater flow model has been calibrated for the Nasia sub-catchment of the White Volta Basin. This model has been validated through a stochastic parameter randomization process and used to evaluate the impacts of groundwater abstraction scenarios on resource sustainability in the basin. A total of 1500 equally likely model realizations of the same terrain based on 1500 equally likely combinations of the data of the key aquifer input parameters were calibrated and used for the scenario analysis. This was done to evaluate model non-uniqueness arising from uncertainties in the key aquifer parameters especially hydraulic conductivity and recharge by comparing the realizations and statistically determining the degree to which they differ from each other. Parameter standard deviations, computed from the calibrated data of the key parameters of hydraulic conductivity and recharge, were used as a yardstick for evaluating model non-uniqueness. All model realizations suggest horizontal hydraulic conductivity estimates in the range of 0.03–78.4 m/day, although over 70 % of the area has values in the range of 0.03–14 m/day. Low standard deviations of the horizontal hydraulic conductivity estimates from the 1500 solutions suggest that this range adequately reflects the properties of the material in the terrain. Lateral groundwater inflows and outflows appear to constitute significant components of the groundwater budgets in the terrain, although estimated direct vertical recharge from precipitation amounts to about 7 % of annual precipitation. High potential for groundwater development has been suggested in the simulations, corroborating earlier estimates of groundwater recharge. Simulation of groundwater abstraction scenarios suggests that the domain can sustain abstraction rates of up to 200 % of the current estimated abstraction rates of 12,960 m3/day under the current recharge rates. Decreasing groundwater recharge by 10 % over a 20-year period will not significantly alter the results of this abstraction scenario. However, increasing abstraction rates by 300 % over the period with decreasing recharge by 10 % will lead to drastic drawdowns in the hydraulic head over the entire terrain by up to 6 m and could cause reversals of flow in most parts of the terrain.

Optimal positioning of groundwater supply wells in residential areas with uncertain information

A simulation-optimisation based methodology has been proposed for identifying economically and ecologically optimal locations for new groundwater supply wells. The purpose of optimisation was to find cost effective extraction locations with a minimum possibility of getting contaminated or drying out within a reasonable time period. A simulation model developed with MODFLOW (modular three dimensional finite-difference groundwater flow model) and MT3DMS (modular three dimensional multispecies transport model) was used to determine the spatiotemporal effects of potential pollution sources and water withdrawals. Monte Carlo method was used with the simulation models to incorporate the uncertainty in the behaviour of potential pollution sources and water extractions. This integrated methodology was illustrated using a small hypothetical case study. The results indicate that readily invisible hydro-geological factors such as heterogeneous characteristics of subsurface strata, irregular gradients, and varying aquifer thickness have a significant influence on the sustainability of a water supply well. The well positioning decisions recommended by the proposed model can be explained and justified based on scientific data. It finds potentially feasible and sustainable locations for new water supply wells, given uncertain information on future events. Since the uncertainty of available information is taken into account, this methodology is suitable for locating wells in poorly understood aquifers utilised for residential supply. The same methodology can be used to determine landfill locations, minimising negative environmental impacts.