Modular Finite-difference Ground-water Flow Research Articles

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.

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

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.

Assessing the effect of urbanization on regional-scale surface water-groundwater interaction and nitrate transport

Identifying regional-scale surface water-groundwater interactions (SGI) is vital for predicting anthropogenic effects on surface water bodies and underlying aquifers. However, large-scale water and nutrient flux studies rely on surface water or groundwater-focused models. This study aims to model the effect of urbanization, which is usually accompanied by high groundwater abstraction and surface water pollution, particularly in the developing world, on a regional-scale SGI and nitrate loading. In the study area, the urban expansion increased by over 3% in the last decade. The integrated SWAT-MODFLOW model, Soil and Water Assessment Tool (SWAT) and Modular Finite-Difference Groundwater Flow (MODFLOW) coupling code, was used to assess SGI. By coupling SWAT-MODFLOW with Reactive Transport in 3-Dimensions, the nutrient loading to the river from point and non-point sources was also modeled. Basin average annual results show that groundwater discharge declined with increasing groundwater abstraction and increased with Land use/Land cover (LULC) changes. Groundwater recharge decreased significantly in the Belge season (February to May), and the river seepage and groundwater discharge decreased correspondingly. High spatiotemporal changes in SGI and nitrate loading were found under the combined LULC and groundwater abstraction scenarios. The water yield decreased by 15%. In a large part of the region, the nitrate loading increased by 17–250%. Seasonally controlled groundwater abstraction and water quality monitoring are essential in this region.

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.

Assessing the Effect of Land/Use Land Cover and Climate Change on Water Yield and Groundwater Recharge in East African Rift Valley using Integrated Model

Study regionEast African Rift Valley basin. Study focusWater availability in the rift valley relies heavily on the discharge from the highlands to rivers that run to the rift floor. This research explores the effect of Land use/Land cover (LULC) and climate change on water yield and groundwater recharge (WYGR) using coupled SWAT-MODFLOW, which integrates Soil and Water Assessment Tool (SWAT) and Newton Modular Finite Difference Groundwater Flow (MODFLOW-NWT). The LULC change was analyzed using artificial neural network-based cellular automata. New hydrological insightsThe dominant LULC is cultivated land and expanded by 5% to the forest and grassland areas. The average temperature and precipitation are expected to rise by 8–11% and 3–6%, respectively. Climate change affects the spatiotemporal distribution of WYGR significantly, while LULC change has a trivial effect. Under the baseline scenario, the recharge was 10% of the average annual precipitation, but climate change is projected to reduce it by 47–53%. Water yield reduction up to 48% and change of perennial rivers to intermittent are expected in the coming decades. The region will experience water scarcity, emerging mainly from climate change.

Recent progress in coupled surface–ground water models and their potential in watershed hydro-biogeochemical studies: A review

Abstract Interactions between surface water (SW) and groundwater (GW) have been a focus of watershed hydrology research for a long time. A holistic perspective on integrated SW–GW modeling approach is necessary to understand the hydrological and biogeochemical processes of these two interconnected systems within the watershed. This paper reviewed the progress and coupling strategy of one important SW model (Soil and Water Assessment Tool, SWAT) and GW model (Modular Finite Difference Groundwater Flow, MODFLOW) since 1999. Three main stages of development of coupled SWAT–MODFLOW model are reflected by the high citation of publications by three pioneer studies, which are Sophocleous et al. (1999), Kim et al. (2008) and Bailey et al. (2016). Currently, the research scope of coupled SWAT–MODFLOW models is focused on hydrologic processes, solute transport and the effects of climate change and human activity on water resources. Major uncertainties of SWAT–MODFLOW from model structure, database and parameterization are discussed. In an era of big data, the coupled SWAT–MODFLOW model has great potential to improve understanding of hydro-biogeochemical processes and support sustainable water and ecological management in the watershed.

Assessment of Groundwater Recharge in Agro-Urban Watersheds Using Integrated SWAT-MODFLOW Model

Numerical models are employed widely to evaluate the hydrological components of a watershed but, traditionally, watershed models simplify either surface or subsurface flow module. In this setup, as a bridge between groundwater and surface water regimes, aquifer recharge is the most affected segment of the water balance. Since the watershed processes are increasingly changed, the need for a comprehensive model with detailed conceptualizing capacity of both groundwater and surface water flow systems is growing. This work focuses on the spatiotemporal groundwater recharge assessment in gauged and ungauged agro-urban watersheds in South Korea using the updated SWAT-MODFLOW model, which integrates the Soil and Water Assessment Tool (SWAT2012) and Newton–Raphson formulation for Modular Finite Difference Groundwater Flow (MODFLOW-NWT) in a single executable code. Before coupling, the setup, calibration, and verification of each model were performed separately. After integration, irrigation pumps and drain cells mapping to SWAT auto-irrigation and subbasins were initiated. Automatic calibration techniques were used for SWAT and MODFLOW-NWT models, but a manual calibration was used for the integrated model. A physical similarity approach was applied to transfer parameters to the ungauged watershed. Statistical model performance indicators revealed that the low streamflow estimation was improved in SWAT-MODFLOW. The spatiotemporal aquifer recharge distribution from both the stream seepage and precipitation showed a substantial change, and most of the aquifer recharge occurs in July–September. The areal annual average recharge reaches about 18% of the precipitation. Low-lying areas receive higher recharge consistently throughout a year. Overall, SWAT-MODFLOW exhibited reasonable versatility in evaluating watershed processes and produced valuable results with reasonable accuracy. The results can be an important input for policymakers in the development of sustainable groundwater protection and abstraction strategies for the region.

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%.

Investigating effects of climate change, urbanization, and sea level changes on groundwater resources in a coastal aquifer: an integrated assessment

Urbanization and climate change are causing numerous side effects on groundwater resources. In this study, an integrated modeling approach by linking soil and water application tool (SWAT), modular finite difference groundwater flow (MODFLOW), and three-dimensional variable-density groundwater flow coupled with multi-species solute and heat transport (SEAWAT) models were used to exhibit responses of groundwater systems, in terms of flow and salt concentrations to current and future climatic and anthropogenic changes. Future climate scenarios for periods of 2010-2040 were generated from the Canadian Global Coupled Model (CGCM) for scenarios A1B, B1, and A2 which was downscaled by the Long Ashton Research Station weather generator (LARS-WG) providing precipitation and temperature patterns for the period 2018-2040. The GCM's outputs were applied to SWAT model to estimate recharge rate for the ten scenarios designed to assess the sensitivity of the aquifer to urbanization and climate change. The estimated recharge rate from SWAT was utilized as an input in numerical groundwater model to evaluate saltwater intrusion (SWI), changes in freshwater storage within the aquifer system, and changes in groundwater level. Based on the results of each scenario's simulation, increase of pumping rate yield by future population growth will have more adverse effects on the unconfined aquifer. The derived information from this study can be used to improve future works by developing a better understanding of the managed and unmanaged response of freshwater storage and unconfined groundwater systems to climate change and anthropogenic activities.

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.

Modeling hydrology, groundwater recharge and non-point nitrate loadings in the Himalayan Upper Yamuna basin

The mountainous Himalayan watersheds are important hydrologic systems responsible for much of the water supply in the Indian sub-continent. These watersheds are increasingly facing anthropogenic and climate-related pressures that impact spatial and temporal distribution of water availability. This study evaluates temporal and spatial distribution of water availability including groundwater recharge and quality (non-point nitrate loadings) for a Himalayan watershed, namely, the Upper Yamuna watershed (part of the Ganga River basin). The watershed has an area of 11 600km2 with elevation ranging from 6300 to 600m above mean sea level. Soil and Water Assessment Tool (SWAT), a physically-based, time-continuous model, has been used to simulate the land phase of the hydrological cycle, to obtain streamflows, groundwater recharge, and nitrate (NO3) load distributions in various components of runoff. The hydrological SWAT model is integrated with the MODular finite difference groundwater FLOW model (MODFLOW), and Modular 3-Dimensional Multi-Species Transport model (MT3DMS), to obtain groundwater flow and NO3 transport. Validation of various modules of this integrated model has been done for sub-basins of the Upper Yamuna watershed. Results on surface runoff and groundwater levels obtained as outputs from simulation show a good comparison with the observed streamflows and groundwater levels (Nash–Sutcliffe and R2 correlations greater than +0.7). Nitrate loading obtained after nitrification, denitrification, and NO3 removal from unsaturated and shallow aquifer zones is combined with groundwater recharge. Results for nitrate modeling in groundwater aquifers are compared with observed NO3 concentration and are found to be in good agreement. The study further evaluates the sensitivity of water availability to climate change. Simulations have been made with the weather inputs of climate change scenarios of A2, B2, and A1B for end of the century. Water yield estimates under climate change scenarios have been made and implications on groundwater and groundwater quality have been assessed. The delicate groundwater resource balance that connects livelihoods of millions of people seems to be under tremendously increasing pressure due to the dynamic conditions of the natural environment of the region and the future climate changes.

Mathematical modelling of effects of Irawan irrigation project water abstractions on the Murzuq aquifer systems in Libya

The Murzuq basin in southwest Libya contains some of the main aquifers providing water for meeting the various water demands in the country. In particular, the Murzuq basin serves a number of irrigation agricultural development projects, including the large-scale Irawan Agricultural project. However, despite its strategic significance for the overall water balance in the country, very limited studies have been undertaken on the Murzuq to determine the long term impacts of the extensive water abstractions taking place in the basin. The aim of this study was to develop and apply a modular finite-difference groundwater flow (MODFLOW) model of the Murzuq. Extensive validation of the model showed it to be capable of adequately reproducing historic water levels within the aquifer. The validated transient model was then used to assess the impacts of medium and long-term water abstractions at Irawan on the piezometric levels in the aquifer. The results show that, with current farming practices at Irawan, the piezometric surface in the centre of the field closest to the cluster of the pumping wells will stabilize in year 2033 at 470 m.a.s.l., representing a maximum drawdown of 30 m. Further significant depression may not occur unless agricultural practices change, such as through an increase in the area cultivated or change in crops grown.

Simulation of groundwater flow and environmental effects resulting from pumping

In coastal lowland plains, increased water demand on a limited water resource has resulted in declining groundwater levels, land subsidence and saltwater encroachment. In southwestern Kyushu, Japan, a sinking of the land surface due to over pumping of groundwater has long been recognized as a problem in the Shiroishi lowland plain. In this paper, an integrated model was established for the Shiroishi site using the modular finite difference groundwater flow model, MODFLOW, by McDonald and Harbaugh (1988) and the modular three-dimensional finite difference groundwater solute transport model, MT3D, by Zheng (1990) to simulate groundwater flow hydraulics, land subsidence, and solute transport in the alluvial lowland plain. Firstly, problems associated with these groundwater resources were discussed and then the established model was applied. The simulated results show that subsidence rapidly occurs throughout the area with the central prone in the center part of the plain. Moreover, seawater intrusion would be expected along the coast if the current rates of groundwater exploitation continue. Sensitivity analysis indicates that certain hydrogeologic parameters such as an inelastic storage coefficient of soil layers significantly contribute effects to both the rate and magnitude of consolidation. Monitoring the present salinization process is useful in determining possible threats to fresh groundwater supplies in the near future. In addition, the integrated numerical model is capable of simulating the regional trend of potentiometric levels, land subsidence and salt concentration. The study also suggests that during years of reduced surface-water availability, reduction of demand, increase in irrigation efficiency and the utilization of water exported from nearby basins are thought to be necessary for future development of the region to alleviate the effects due to pumping.