Showing papers in "Hydrogeology Journal in 2015"
TL;DR: In this paper, an integrated approach is implemented using remote sensing and geographic information system (GIS)-based multi-criteria evaluation to identify promising areas for groundwater exploration in Raya Valley, northern Ethiopia.
Abstract: Sustainable development and management of groundwater resources require application of scientific principles and modern techniques. An integrated approach is implemented using remote sensing and geographic information system (GIS)-based multi-criteria evaluation to identify promising areas for groundwater exploration in Raya Valley, northern Ethiopia. The thematic layers considered are lithology, lineament density, geomorphology, slope, drainage density, rainfall and land use/cover. The corresponding normalized rates for the classes in a layer and weights for thematic layers are computed using Saaty’s analytical hierarchy process. Based on the computed rates and weights, aggregating the thematic maps is done using a weighted linear combination method to obtain a groundwater potential (GP) map. The GP map is verified by overlay analysis with observed borehole yield data. Map-removal and single-parameter sensitivity analyses are used to examine the effects of removing any of the thematic layers on the GP map and to compute effective weights, respectively. About 770 km2 (28 % of the study area) is designated as ‘very good’ GP. ‘Good’, ‘moderate’ and ‘poor’ GP areas cover 630 km2 (23 %), 600 km2 (22 %) and 690 km2 (25 %), respectively; the area with ‘very poor’ GP covers 55 km2 (2 %). Verification of the GP map against observed borehole yield data shows 74 % agreement, which is fairly satisfactory. The sensitivity analyses reveal the GP map is most sensitive to lithology with a mean variation index of 6.5 %, and lithology is the most effective thematic layer in GP mapping with mean effective weight of 52 %.
136 citations
TL;DR: In this article, a generalized conceptual gravity-driven regional groundwater flow (GDRGF) model is proposed for an unconfined and confined carbonate region in the Transdanubian Range (TR), Hungary.
Abstract: Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock–water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.
80 citations
TL;DR: In this article, the authors examined the economic costs of pumping replacement groundwater during drought and the potential loss of pumping capacity as groundwater levels drop in California's Central Valley, showing that places without access to groundwater and with uncertain surface-water deliveries during drought are the most economically vulnerable in terms of crop revenues, employment and household income.
Abstract: As in many places, groundwater in California (USA) is the major alternative water source for agriculture during drought, so groundwater’s availability will drive some inevitable changes in the state’s water management. Currently, agricultural, environmental, and urban uses compete for groundwater, resulting in substantial overdraft in dry years with lowering of water tables, which in turn increases pumping costs and reduces groundwater pumping capacity. In this study, SWAP (an economic model of agricultural production and water use in California) and C2VISim (the California Department of Water Resources groundwater model for California’s Central Valley) are connected. This paper examines the economic costs of pumping replacement groundwater during drought and the potential loss of pumping capacity as groundwater levels drop. A scenario of three additional drought years continuing from 2014 show lower water tables in California’s Central Valley and loss of pumping capacity. Places without access to groundwater and with uncertain surface-water deliveries during drought are the most economically vulnerable in terms of crop revenues, employment and household income. This is particularly true for Tulare Lake Basin, which relies heavily on water imported from the Sacramento-San Joaquin Delta. Remote-sensing estimates of idle agricultural land between 2012 and 2014 confirm this finding. Results also point to the potential of a portfolio approach for agriculture, in which crop mixing and conservation practices have substantial roles.
77 citations
TL;DR: In this article, the authors present a review of the state-of-the-art tools for coastal groundwater management (CGM) in terms of their performance and choice of robust tools such as EAs, surrogate models, and parallel processing techniques.
Abstract: Decision models are essential tools for coastal groundwater management (CGM). A combined simulation-optimization framework is employed to develop these models. One of the main barriers in the widespread application of these models for real-world cases is their large computational burden. Recent advances in efficient computational approaches and robust optimization methods can crack this barrier. This study surveys the scientific basis of CGM to provide an overview on this subject and reviews the-state-of-the-art to clarify recent developments and to outline ideas for improving the computational performance. Key details are presented on the performance and choice of possible robust tools such as efficient evolutionary algorithms (EAs), surrogate models, and parallel processing techniques. Then, the potential challenges remaining in this context are scrutinized, demonstrating open fields for further research, which include issues related to advances in simulating and optimizing phases such as introducing new robust algorithms and considering multi-objective purposes, implementing novel and high-performance tools, considering global concerns (e.g. climate change impacts), enhancing the existing models to fit the real world, and taking into account the complexities of real-world applications (e.g. uncertainties in the modeling parameters, and data acquisition). Finally, the outcomes of the systematic review are applied to solve a real-world CGM problem in Iran, to quantitatively examine the performance of combined implementation of some of the suggested tools. It is revealed that the required computational time is considerably reduced by as much as three orders of magnitude when correct combinations of robust EAs, surrogate model, and parallelization technique are utilized.
73 citations
TL;DR: In this article, a replicable multidisciplinary approach for science-based groundwater management practices is presented for sustainable management practices: Bir Al-Nas (Bottom-up Integrated Approach for sustainabLe grouNdwater management in rural areaS).
Abstract: A replicable multidisciplinary approach is presented for science-based groundwater management practices: Bir Al-Nas (Bottom-up IntegRated Approach for sustainabLe grouNdwater mAnagement in rural areaS). This approach provides a practical example of the concept of “socio-hydrogeology”, a way of incorporating the social dimension into hydrogeological investigations, as reinforced by the translation of the Arabic bir al-nas: “the people’s well”. To achieve this, hydrogeologists act as “social hydrologists” during their monitoring activities, which often bring them into contact with local communities and end users (and polluters) of water. Not only can they retrieve reliable information about traditional know-how and local issues, but they can also change the public perception of science/scientists to create the basis for mutual collaboration and understanding in view of implementing improved integrated groundwater management. The final outcomes are expected to be an increased awareness of communities at the local level and a clear understanding of their water issues and needs from the very early stages of the investigation. Although the importance of using such methods in groundwater analysis and management is widely recognized, hydrogeological investigations are currently dominated by sectorial approaches that are easier to implement but less sustainable. The pressure of population growth, the shift towards more water-dependent economies, climate change and its impact on water availability will require scientists to use a more integrated approach, such as Bir Al-Nas, when dealing with increasing water pollution and water-scarcity issues.
72 citations
TL;DR: In this article, the authors review the literature on the application of simulation-optimization approaches for management and monitoring of coastal aquifers and provide an efficient framework for preliminary designs of saltwater-intrusion management schemes.
Abstract: The literature on the application of simulation-optimization approaches for management and monitoring of coastal aquifers is reviewed. Both sharp- and dispersive-interface modeling approaches have been applied in conjunction with optimization algorithms in the past to develop management solutions for saltwater intrusion. Simulation-optimization models based on sharp-interface approximation are often based on the Ghyben-Herzberg relationship and provide an efficient framework for preliminary designs of saltwater-intrusion management schemes. Models based on dispersive-interface numerical models have wider applicability but are challenged by the computational burden involved when applied in the simulation-optimization framework. The use of surrogate models to substitute the physically based model during optimization has been found to be successful in many cases. Scalability is still a challenge for the surrogate modeling approach as the computational advantage accrued is traded-off with the training time required for the surrogate models as the problem size increases. Few studies have attempted to solve stochastic coastal-aquifer management problems considering model prediction uncertainty. Approaches that have been reported in the wider groundwater management literature need to be extended and adapted to address the challenges posed by the stochastic coastal-aquifer management problem. Similarly, while abundant literature is available on simulation-optimization methods for the optimal design of groundwater monitoring networks, applications targeting coastal aquifer systems are rare. Methods to optimize compliance monitoring strategies for coastal aquifers need to be developed considering the importance of monitoring feedback information in improving the management strategies.
67 citations
TL;DR: In this paper, various optimization methods have been used for solving the inverse problem of parameter identification (estimation), experimental design, and groundwater planning and management, including linear programming, quadratic programming, dynamic programming, stochastic programming, nonlinear programming, and global search algorithms such as genetic algorithms, simulated annealing, and tabu search.
Abstract: Optimization methods have been used in groundwater modeling as well as for the planning and management of groundwater systems. This paper reviews and evaluates the various optimization methods that have been used for solving the inverse problem of parameter identification (estimation), experimental design, and groundwater planning and management. Various model selection criteria are discussed, as well as criteria used for model discrimination. The inverse problem of parameter identification concerns the optimal determination of model parameters using water-level observations. In general, the optimal experimental design seeks to find sampling strategies for the purpose of estimating the unknown model parameters. A typical objective of optimal conjunctive-use planning of surface water and groundwater is to minimize the operational costs of meeting water demand. The optimization methods include mathematical programming techniques such as linear programming, quadratic programming, dynamic programming, stochastic programming, nonlinear programming, and the global search algorithms such as genetic algorithms, simulated annealing, and tabu search. Emphasis is placed on groundwater flow problems as opposed to contaminant transport problems. A typical two-dimensional groundwater flow problem is used to explain the basic formulations and algorithms that have been used to solve the formulated optimization problems.
66 citations
TL;DR: A detailed groundwater geochemistry survey was undertaken in the Outaouais Region (Quebec, Canada) in order to identify the primary processes responsible for groundwater quality and to develop a conceptual model for groundwater flow and geochemical evolution as mentioned in this paper.
Abstract: As part of a province-wide groundwater characterization program, a detailed groundwater geochemistry survey was undertaken in the Outaouais Region (Quebec, Canada) in order to identify the primary processes responsible for groundwater quality and to develop a conceptual model for groundwater flow and geochemical evolution During the summers of 2011 and 2012, 139 samples were collected from municipal and private wells which were analysed for major ions, nutrients, trace elements and sulphides About 70 % of the samples were obtained from bedrock wells, mainly in the silicate rocks of the Canadian Shield and the remainder from wells screened in Quaternary deposit aquifers Hydrogeochemical facies distributions were determined from 127 of these samples which had anion-cation charge balance errors within ±10 % The classification by facies was also supported by a multivariate statistical analysis, namely factor analysis combined with hierarchical cluster analysis The study identified Champlain Sea invasion, cation exchange and freshwater recharge as the main geochemical processes affecting groundwater chemistry in this region Secondary processes, related to the bedrock geology, are responsible for exceedances of Canadian drinking-water standards, namely for fluoride, uranium, iron and manganese
63 citations
TL;DR: For example, HydrogeoSieveXL as mentioned in this paper is a spreadsheet program that calculates hydraulic conductivity (K) from grain-size distribution curves using 15 different methods, using the published grain size distribution curves.
Abstract: For over a century, hydrogeologists have estimated hydraulic conductivity (K) from grain-size distribution curves. The benefits of the practice are simplicity, cost, and a means of identifying spatial variations in K. Many techniques have been developed over the years, but all suffer from similar shortcomings: no accounting of heterogeneity within samples (i.e., aquifer structure is lost), loss of grain packing characteristics, and failure to account for the effects of overburden pressure on K. In addition, K estimates can vary by an order of magnitude between the various methods, and it is not generally possible to identify the best method for a given sample. The drawbacks are serious, but the advantages have seen the use of grain-size distribution curves for K estimation continue, often using a single selected method to estimate K in a given project. In most cases, this restriction results from convenience. It is proposed here that extending the analysis to include several methods would be beneficial since it would provide a better indication of the range of K that might apply. To overcome the convenience limitation, an Excel-based spreadsheet program, HydrogeoSieveXL, is introduced here. HydrogeoSieveXL is a freely available program that calculates K from grain-size distribution curves using 15 different methods. HydrogeoSieveXL was found to calculate K values essentially identical to those reported in the literature, using the published grain-size distribution curves.
61 citations
TL;DR: In this paper, a combined SWAT-MODFLOW model was employed to integratively simulate surface-water and groundwater flows in the Neishaboor watershed, Iran, to compute spatial and temporal distributions of hydrologic components.
Abstract: Increased irrigation in the Neishaboor watershed, Iran, during the last few decades has caused serious groundwater depletion, making the development of comprehensive mitigation strategies and tools increasingly important. In this study, SWAT and MODFLOW were employed to integratively simulate surface-water and groundwater flows. SWAT and MODFLOW were iteratively executed to compute spatial and temporal distributions of hydrologic components. The combined SWAT-MODFLOW model was calibrated (2000–2010) and validated (2010–2012) based on streamflow, wheat yield, groundwater extraction, and groundwater-level data. This multi-criteria calibration procedure provided greater confidence for the partitioning of water between soil storage, actual evapotranspiration, and aquifer recharge. The SWAT model provided satisfactory predictions of the hydrologic budget for the watershed outlet. It also provided good predictions of irrigated wheat yield and groundwater extraction. The 10-year mean annual recharge rate estimated using the combined model varied greatly, ranging from 0 to 960 mm, with an average of 176 mm. This result showed good agreement with the independently estimated annual recharge rate from an earlier study. The combined model provides a robust tool for the sustainable planning and management of water resources for areas with stressed aquifers where interaction between groundwater and surface water cannot be easily assessed.
60 citations
TL;DR: In this article, the characteristics and mechanism of land subsidence and uplift are analyzed and discussed on the basis of field and laboratory data, and the deformation of aquifer and aquitard units consists of elastic, plastic, visco-elastic components.
Abstract: Increasing artificial water recharge and restriction on groundwater pumpage have caused land displacements in Shanghai (China) to shift from subsidence to uplift. On the basis of field and laboratory data, the characteristics and mechanism of land subsidence and uplift are analyzed and discussed. Under the condition of long-term groundwater extraction, the deformation of aquifer and aquitard units consists of elastic, plastic, visco-elastic, and visco-plastic components. The recoverable elastic and visco-elastic deformation is only a small portion of the total deformation for both aquitard and aquifer units, especially when the groundwater level in the units is lower than the historically lowest values. When the groundwater level in aquifer and aquitard units rises, whether their expansion occurs immediately or not, depends on the changing modes of groundwater level they have experienced. Even aquifer units do not always rebound closely following the rise of groundwater level in them. The lagging of the occurrence of arrested land subsidence and uplift, clearly behind the rise of groundwater level in aquifer units, can be attributed to the visco-plastic deformation of all units and the consolidation deformation of aquitard units. Artificial recharge and limitation of pumpage are efficient measures for controlling land subsidence, but earlier actions are necessary to keep groundwater levels in all aquifer units above their historically lowest values all the time, if a more effective outcome is expected.
TL;DR: In this paper, the analytical and empirical approaches available to describe the flow of groundwater towards a well are summarized, and the most commonly used parameter of well design is the entrance velocity, however, considerable debate about which value from the literature should be used.
Abstract: Water wells are an indispensable tool for groundwater extraction. The analytical and empirical approaches available to describe the flow of groundwater towards a well are summarized. Such flow involves a strong velocity increase, especially close to the well. The linear laminar Darcy approach is, therefore, not fully applicable in well hydraulics, as inertial and turbulent flow components occur close to and inside the well, respectively. For common well set-ups and hydraulic parameters, flow in the aquifer is linear laminar, non-linear laminar in the gravel pack, and turbulent in the screen and the well interior. The most commonly used parameter of well design is the entrance velocity. There is, however, considerable debate about which value from the literature should be used. The easiest way to control entrance velocity involves the well geometry. The influence of the diameter of the screen and borehole is smaller than that of the screen length. Minimizing partial penetration can help to curb head losses.
TL;DR: In this article, an accurate model was developed for solving problems of groundwater-pollution-source identification, and the numerical simulations of flow and pollutant transport in groundwater were carried out using MODFLOW and MT3DMS software.
Abstract: In this study, an accurate model was developed for solving problems of groundwater-pollution-source identification. In the developed model, the numerical simulations of flow and pollutant transport in groundwater were carried out using MODFLOW and MT3DMS software. The optimization processes were carried out using a differential evolution algorithm. The performance of the developed model was tested on two hypothetical aquifer models using real and noisy observation data. In the first model, the release histories of the pollution sources were determined assuming that the numbers, locations and active stress periods of the sources are known. In the second model, the release histories of the pollution sources were determined assuming that there is no information on the sources. The results obtained by the developed model were found to be better than those reported in literature.
TL;DR: In this article, the authors demonstrated that the raw water-balance estimates of recharge had a negative bias of 45mm/yr when compared to 190 recharge estimates using the water-table fluctuation method over a 10-year period (2001-2010).
Abstract: Using a water balance to estimate groundwater recharge through the use of remotely sensed evapotranspiration offers a spatial and temporal density of data that other techniques cannot match. However, the estimates are uncertain and therefore ground truthing of the recharge estimates is necessary. This study, conducted in the south-east of South Australia, demonstrated that the raw water-balance estimates of recharge had a negative bias of 45 mm/yr when compared to 190 recharge estimates using the water-table fluctuation method over a 10-year period (2001–2010). As this bias was not related to the magnitude of the recharge estimated using the water-table fluctuation method, a simple offset was used to bias-correct the water-balance recharge estimates. The bias-corrected recharge estimates had a mean residual that was not significantly different from an independent set of 99 historical recharge estimates but did have a large mean absolute residual indicating a lack of precision. The value in this technique is the density of the data (250-m grid over 29,000 km2). The relationship between the water-table depth and net recharge under different vegetation types was investigated. Under pastures, there was no relationship with water-table depth, as the shallow roots do not intercept groundwater. However, under plantation forestry, there was a relationship between net recharge and water-table depth. Net recharge under plantation forestry growing on sandy soils was independent of the water table at around 6 m depth but, under heavier textured soils, the trees were using groundwater from depths of more than 20 m.
TL;DR: In this article, five data-driven models were examined for the forecasting of groundwater levels as a result of recharge via tailings from an abandoned mine in Quebec, Canada, for lead times of 1 day, 1 week and 1 month.
Abstract: Several groundwater-level forecasting studies have shown that data-driven models are simpler, faster to develop, and provide more accurate and precise results than physical or numerical-based models. Five data-driven models were examined for the forecasting of groundwater levels as a result of recharge via tailings from an abandoned mine in Quebec, Canada, for lead times of 1 day, 1 week and 1 month. The five models are: a multiple linear regression (MLR); an artificial neural network (ANN); two models that are based on de-noising the model predictors using the wavelet-transform (W-MLR, W-ANN); and a W-ensemble ANN (W-ENN) model. The tailing recharge, total precipitation, and mean air temperature were used as predictors. The ANN models performed better than the MLR models, and both MLR and ANN models performed significantly better after de-noising the predictors using wavelet-transforms. Overall, the W-ENN model performed best for each of the three lead times. These results highlight the ability of wavelet-transforms to decompose non-stationary data into discrete wavelet-components, highlighting cyclic patterns and trends in the time-series at varying temporal scales, rendering the data readily usable in forecasting. The good performance of the W-ENN model highlights the usefulness of ensemble modeling, which ensures model robustness along with improved reliability by reducing variance.
TL;DR: In this paper, the storage-discharge relationship of 26 watersheds in the inland Pacific Northwest of the United States were analyzed and four fitting methods were used to obtain the baseflow coefficients: lower envelope, organic correlation, and ordinary and inverse least squares.
Abstract: The storage-discharge relationships of 26 watersheds in the inland Pacific Northwest of the United States were analyzed Four fitting methods were used to obtain the baseflow coefficients: lower envelope, organic correlation, and ordinary and inverse least squares Several climatic and terrain attributes were evaluated as predictors of baseflow coefficients Watersheds dominated by basalt and flatter landscapes exhibited the smallest recession time scales (K) (125–200 days) Greater K values (333–667 days) were obtained over catchments dominated by metamorphic and sedimentary rocks Mean basin slope and the aridity index were found to be the best estimators of baseflow coefficients Baseflow in flat basalt landscapes, located in dry warm climates, decrease rapidly during summer months and are most sensitive to future droughts and warming climates Groundwater systems feeding streams during the driest months can drop to less than 1 mm of effective storage in these sensitive systems In contrast, the minimum annual storage in mountainous systems can have greater than 10 mm effective storage By understanding the main factors controlling baseflow recession characteristics, environmental agencies could prioritize efforts in areas where future droughts and land use changes may affect ecological assemblages and socio-economic activities
TL;DR: In this paper, the authors presented an approach to calibrate a large-scale groundwater flow model using the monthly Gravity Recovery and Climate Experiment (GRACE) satellite data, which have been available globally on a spatial grid of 1° in the geographic coordinate system since 2002.
Abstract: Traditional numerical models usually use extensive observed hydraulic-head data as calibration targets. However, this calibration process is not applicable in remote areas with limited or no monitoring data. This study presents an approach to calibrate a large-scale groundwater flow model using the monthly Gravity Recovery and Climate Experiment (GRACE) satellite data, which have been available globally on a spatial grid of 1° in the geographic coordinate system since 2002. A groundwater storage anomaly isolated from the terrestrial water storage (TWS) anomaly is converted into hydraulic head at the center of the grid, which is then used as observed data to calibrate a numerical model to estimate aquifer hydraulic conductivity. The aquifer system in the remote and hyperarid Qaidam Basin, China, is used as a case study to demonstrate the applicability of this approach. A groundwater model using FEFLOW is constructed for the Qaidam Basin and the GRACE-derived groundwater storage anomaly over the period 2003–2012 is included to calibrate the model, which is done using an automatic estimation method (PEST). The calibrated model is then run to output hydraulic heads at three sites where long-term hydraulic head data are available. The reasonably good fit between the calculated and observed hydraulic heads, together with the very similar groundwater storage anomalies from the numerical model and GRACE data, demonstrate that this approach is generally applicable in regions of groundwater data scarcity.
TL;DR: In this article, a three-dimensional numerical model was developed and applied, to predict the plume dynamics and pressure propagation, and in the assessment of storage safety, and the model was assembled with the most recent data and the simulations are calibrated to the latest available observations.
Abstract: Saline formations are considered to be candidates for carbon sequestration due to their great depths, large storage volumes, and widespread occurrence. However, injecting carbon dioxide into low-permeability reservoirs is challenging. An active demonstration project for carbon dioxide sequestration in the Ordos Basin, China, began in 2010. The site is characterized by a deep, multi-layered saline reservoir with permeability mostly below 1.0 × 10−14 m2. Field observations so far suggest that only small-to-moderate pressure buildup has taken place due to injection. The Triassic Liujiagou sandstone at the top of the reservoir has surprisingly high injectivity and accepts approximately 80 % of the injected mass at the site. Based on these key observations, a three-dimensional numerical model was developed and applied, to predict the plume dynamics and pressure propagation, and in the assessment of storage safety. The model is assembled with the most recent data and the simulations are calibrated to the latest available observations. The model explains most of the observed phenomena at the site. With the current operation scheme, the CO2 plume at the uppermost reservoir would reach a lateral distance of 658 m by the end of the project in 2015, and approximately 1,000 m after 100 years since injection. The resulting pressure buildup in the reservoir was below 5 MPa, far below the threshold to cause fracturing of the sealing cap (around 33 MPa).
TL;DR: In this paper, the authors quantified the spatio-temporal distribution of the recharge, through combined use of isotopic characterization of the different components of the water cycle and a rainfall-runoff model.
Abstract: Closed basins are catchments whose drainage networks converge to lakes, salt flats or alluvial plains. Salt flats in the closed basins in arid northern Chile are extremely important ecological niches. The Salar del Huasco, one of these salt flats located in the high plateau (Altiplano), is a Ramsar site located in a national park and is composed of a wetland ecosystem rich in biodiversity. The proper management of the groundwater, which is essential for the wetland function, requires accurate estimates of recharge in the Salar del Huasco basin. This study quantifies the spatio-temporal distribution of the recharge, through combined use of isotopic characterization of the different components of the water cycle and a rainfall-runoff model. The use of both methodologies aids the understanding of hydrological behavior of the basin and enabled estimation of a long-term average recharge of 22 mm/yr (i.e., 15 % of the annual rainfall). Recharge has a high spatial variability, controlled by the geological and hydrometeorological characteristics of the basin, and a high interannual variability, with values ranging from 18 to 26 mm/yr. The isotopic approach allowed not only the definition of the conceptual model used in the hydrological model, but also eliminated the possibility of a hydrogeological connection between the aquifer of the Salar del Huasco basin and the aquifer that feeds the springs of the nearby town of Pica. This potential connection has been an issue of great interest to agriculture and tourism activities in the region.
TL;DR: In this article, the authors analyzed the contribution of individual components to total head loss (drawdown) in the well and found that well development is the most important measure to influence well performance and energy efficiency.
Abstract: Knowledge about the hydraulics of water wells is important to optimize their energy efficiency. By minimizing head losses around the well, energy consumption and ageing processes can be limited, thereby prolonging the well’s service life. The contribution of the individual components to total head loss (drawdown) in the well is analyzed in detail. The single most important contributor to drawdown is commonly the aquifer. Its hydraulic conductivity can only be improved slightly through development. The second most important contributor is the formation of a wellbore skin layer. This occurs if no proper well development was performed after drilling; the layer contains remnants of drilling-fluid additives or mobilized fine aquifer particles. The head loss caused by groundwater flow in the gravel pack, through the screen slots and inside the well, was found to be small. Thus, well development is the most important measure to influence well performance and energy efficiency. For longer operation times and pumped volumes, the energy gains outperform the cost for the development.
TL;DR: In this article, a combination of hydrogeochemical tracers, stable isotopes, and radiocarbon methods was used to investigate the groundwater recharge and evolution in the Shule River basin, Northwest China.
Abstract: Groundwater recharge and evolution in the Shule River basin, Northwest China, was investigated by a combination of hydrogeochemical tracers, stable isotopes, and radiocarbon methods. Results showed the general chemistry of the groundwater is of SO4
2− type. Water–rock reactions of halite, Glauber’s salt, gypsum and celestite, and reverse ionic exchange dictated the groundwater chemistry evolution, increasing concentrations of Cl−, Na+, SO4
2−, Ca2+, Mg2+ and Sr2+ in the groundwater. The δ18O and δ2H values of groundwater ranged from −10.8 to −7.7 and −74.4 to −53.1 ‰, respectively. Modern groundwater was identified in the proluvial fan and the shallow aquifer of the fine soil plain, likely as a result of direct infiltration of rivers and irrigation returns. Deep groundwater was depleted in heavy isotopes with 14C ages ranging from 3,000 to 26,000 years, suggesting palaeowater that was recharged during the late Pleistocene and middle Holocene epochs under a cold climate. These results have important implications for groundwater management in the Shule River basin, since large amounts of groundwater are effectively being mined and a water-use strategy is urgently needed.
TL;DR: In this paper, the authors explore the individual effect of flow velocity and layered lenses on a DNAPL (PCE) migration in porous media, and show that large flow velocity significantly promotes lateral and vertical migration of the low-viscosity phase liquids, while when layered lenses exist, the infiltration rate decreases and horizontal spread increases.
Abstract: Understanding the migration of dense non-aqueous phase liquids (DNAPLs) in complex subsurface systems is important for evaluating contamination source zones and designing remediation schemes after spill events. Six sandbox experiments were performed to explore the individual effect of flow velocity, and the combined effect of flow velocity and layered lenses on a DNAPL (PCE) migration in porous media. DNAPL saturation was measured using a light transmission system, and saturation distribution was quantified by spatial moments. The experimental results show that large flow velocity significantly promotes lateral and vertical migration of the low-viscosity DNAPL, while when layered lenses exist, the infiltration rate decreases and horizontal spread increases. Migration processes were numerically simulated, and the modelling results tested against experimental results. Furthermore, migration of DNAPLs with different viscosities was simulated to explore the combined effects of flow velocity and geological heterogeneity. Simulation results show that enhanced heterogeneity makes low-viscosity DNAPLs migrate along preferential pathways, resulting in irregular DNAPL morphology. Layered lenses combined with heterogeneity complicate the effect of flow velocity on the migration of low-viscosity DNAPLs by changing percolation paths. Results also demonstrate that flow velocity exhibits relatively little influence on the migration of medium/high-viscosity DNAPLs, which is predominantly controlled by viscosity and heterogeneity. Enhanced heterogeneity has a larger effect on migration behavior. Findings indicate that the migration paths and position of the source zone could change significantly, due to the combined effect of groundwater flow velocity and geological heterogeneity; thus, comprehensive hydrogeological investigation is needed to characterize the source zone.
TL;DR: In this article, a field experiment was carried out in southern Xinjiang, China, to reveal soil-water flow pattern beneath a combined plastic-mulch (film) and drip-irrigation system using brackish water.
Abstract: A field experiment was carried out in southern Xinjiang, China, to reveal soil-water flow pattern beneath a combined plastic-mulch (film) and drip-irrigation system using brackish water. The soil-water flow system (SWFS) was characterized from soil surface to the water table based on observed spatio-temporal distribution of total soil-water potential, water content and electric conductivity. Root suction provided a strong inner sink. The results indicated that SWFS determined the soil salinity and moisture distribution. Drip-irrigation events could leach excess salts from the root zone and provide soil conditions with a tolerable salinity level that supports the growth of cotton. High-salinity strips were formed along the wetting front and at the bare soil surface. Hydrogeology conditions, irrigation regime, climate, plant growth and use of mulch would affect potential sources and sinks, boundary conditions and the size of the SWFS. At depth 0–60 cm, the soil salinity at the end of the irrigation season was 1.9 times that at the beginning. Beneath the mulch cover, the soil-water content in the ‘wide rows’ zone (55 cm between the two rows with no drip line) was higher than that in the ‘narrow rows’ zone (15 cm between the two rows with a drip line) due to the strong root-water uptake. The downward water flow below the divergent curved surface of zero flux before irrigation, and the water-table fluctuation with irrigation events, indicated that excessive irrigation occurred.
TL;DR: In this paper, a simple and efficient method for estimating seawater-groundwater exchange rate was proposed, based on field measurements of groundwater hydraulic head, temperature and salinity, and the results were interpolated and integrated along the whole transect.
Abstract: The exchange rate between seawater and groundwater in a tidal flat was investigated at Laizhou Bay, China, where there are large-scale seepage faces with horizontal extension of several hundred meters developed during low tides. Taking into account the effects of seepage face and density, a simple and efficient method for estimating seawater–groundwater exchange rate is proposed, based on field measurements of groundwater hydraulic head, temperature and salinity. First, the exchange rate at each well was obtained using the generalized Darcy’s law, then the results were interpolated and integrated along the whole transect. The total submarine groundwater discharge (SGD) and inflow were estimated to be 8.8 and 15.3 m3 d−1 m−1, respectively. The spatial distributions of SGD and inflow were different from those of sandy or gravel beaches possibly owing to the low-permeability sediment (silty sand with mud), very gentle slope, and the large-scale seepage faces. A freshwater discharge tube was identified near the low-tide line, as evidenced by significant increase in outflow and low salinity of groundwater observed there. The SGD from the seepage faces accounted for ∼21 % of the total SGD. The outflow rate that occurred from the seepage faces, and the ratio of the outflow from the seepage faces to the total outflow, decreased seaward significantly and monotonically.
TL;DR: In this paper, the evolution of hydrodynamic parameters (transmissivity and storage coefficient) by depth in the south Indian context is quantified using falling-head borehole permeameter tests, injection tests, flowmeter profiles, singlepacker tests and pumping tests were carried out in the unsaturated saprolite and saturated fractured granite.
Abstract: Due to extensive irrigation, most crystalline aquifers of south India are overexploited. Aquifer structure consists of an upper weathered saprolite followed by a fractured zone whose fracture density decreases with depth. To achieve sustainable management, the evolution of hydrodynamic parameters (transmissivity and storage coefficient) by depth in the south Indian context should be quantified. Falling-head borehole permeameter tests, injection tests, flowmeter profiles, single-packer tests and pumping tests were carried out in the unsaturated saprolite and saturated fractured granite. Results show that the saprolite is poorly transmissive (T fs = 3 × 10–7 to 8.5 × 10–8 m2 s–1) and that the most conductive part of the aquifer corresponds to the bottom of the saprolite and the upper part of the fractured rock (T = 1.0 × 10–3 to 7.0 × 10–4 m2 s–1). The transmissivity along the profile is mostly controlled by two distinct conductive zones without apparent vertical hydraulic connection. The transmissivity and storage coefficient both decrease with depth depending on the saturation of the main fracture zones, and boreholes are not exploitable after a certain depth (27.5 m on the investigated section). The numerous investigations performed allow a complete quantification with depth of the hydrodynamic parameters along the weathering profile, and a conceptual model is presented. Hydrograph observations (4 years) are shown to be relevant as a first-order characterization of the media and diffusivity evolution with depth. The evolution of these hydrodynamic parameters along the profile has a great impact on groundwater prospecting, exploitation and transport properties in such crystalline rock aquifers.
TL;DR: In this article, structural and hydrogeological data are combined to interpret the hydraulic-head drop measured across a fault with tens of meters of oblique-slip, which is interpreted to be a result of the low-permeability shaley fault rock.
Abstract: Faults influence groundwater flow paths. The transport of groundwater contaminants within the faulted sandstones and shales of Chatsworth Formation exposed in southern California, USA, have been investigated. Structural and hydrogeological data are combined to interpret the hydraulic-head drop measured across a fault with tens of meters of oblique-slip. The fault zone architecture was delineated at two locations: an outcrop and a borehole intersecting the fault at depth. At the first station, the fault juxtaposes sandstones against shales with a fault core mostly consisting of deformed shale. A series of shale beds striking parallel to the fault zone and dipping ∼50° toward the fault zone provides evidence that the shale was incorporated into the fault zone. At the second station, borehole images show a plane juxtaposing fractured sandstone against shale-rich fault rock. Hydraulic heads measured at 30 wells show a drop of 75 m across the fault, which is interpreted to be a result of the low-permeability shaley fault rock. It is proposed that the shale was incorporated into the fault zone by shale smearing. These results are consistent with numerical modeling, which requires a low-permeability fault core to simulate the observed hydraulic head differences. Understanding the hydraulic nature of this fault provides a critical constraint for evaluating the future migration of contaminants in the groundwater system.
TL;DR: In this article, a one-dimensional sedimentation-transport model was developed to simulate the historical conservative transport of the reconstructed pore-water chloride in the marine Quaternary system in Hong Kong.
Abstract: Offshore hydrogeology has been much less studied compared to onshore hydrogeology. The marine Quaternary system in Hong Kong (China) consists of interlayers of aquitards and aquifers and was part of the Pearl River Delta when the sea level was low before the Holocene. Core samples from six offshore boreholes were collected to measure the chloride concentration in the system by adding deionized water. A method was proposed to convert the sediment chloride into that of the original pore water. A one-dimensional sedimentation-transport model was developed to simulate the historical conservative transport of the reconstructed pore-water chloride. The model integrates present knowledge of stratigraphy and the historical evolution of the geological system. The chloride concentration profiles show that the chloride decreases from an average of 13,800 mg/L in the first marine unit to an average of 5,620 mg/L in the first aquifer. At the bottom of one borehole, the concentration is only 1,420 mg/L. The numerical model shows that the vertical chloride distribution is due to diffusion-controlled downward migration of seawater. The second marine unit obstructs the downward migration, indicating its low permeability and good aquitard integrity. The relatively fresh or brackish water in deep aquifers protected by the aquitard has the potential to be used as drinking water following some treatment, or at least as raw water with much cheaper desalinization compared with using seawater. The methodology and findings in this study are instructional for other coastal areas with similar geology and history in the South China Sea.
TL;DR: In this article, a conceptual approach for the study of urban hydrogeological systems is presented, which is based on the features of Bucharest city (Romania) and can be adapted to other urban areas showing similar characteristics.
Abstract: Management of groundwater systems in urban areas is necessary and can be reliably performed by means of mathematical modeling combined with geospatial analysis. A conceptual approach for the study of urban hydrogeological systems is presented. The proposed approach is based on the features of Bucharest city (Romania) and can be adapted to other urban areas showing similar characteristics. It takes into account the interaction between groundwater and significant urban infrastructure elements that can be encountered in modern cities such as subway tunnels and water-supply networks, and gives special attention to the sewer system. In this respect, an adaptation of the leakage factor approach is proposed, which uses a sewer-system zoning function related to the conduits’ location in the aquifer system and a sewer-conduits classification function related to their structural and/or hydraulic properties. The approach was used to elaborate a single-layered steady state groundwater flow model for a pilot zone of Bucharest city.
TL;DR: In this article, a feedback-based methodology is implemented, integrating sequential-monitoring-network design and a source identification method, in order to improve the efficiency of source characterization, and the simulated annealing (SA) optimization algorithm is used to solve the models for optimal source identification and the monitoring-network-design optimization.
Abstract: Often, when pollution is first detected in groundwater, very few spatiotemporal pollutant concentration measurements are available. The contaminant concentration measurement data initially available are generally sparse and insufficient for accurate source characterization. This requires development of a contaminant monitoring plan and its field implementation to collect more data. The location of scientifically chosen monitoring points and the number of measurements are important considerations in improving the source-characterization process, especially in a complex contamination scenario. In order to improve the efficiency of source characterization, a feedback-based methodology is implemented, integrating sequential-monitoring-network design and a source identification method. The simulated annealing (SA) optimization algorithm is used to solve the models for optimal source identification and the monitoring-network-design optimization. This sequence is repeated a few times to improve the accuracy of source characterization. The methodology is based on the premise that concentration measurements from a sequence of implemented monitoring networks provide feedback information on the actual concentration in the site. This additional information, obtained as feedback from monitoring networks designed and implemented based on intermediate source characterization, can result in sequential improvement in the resulting source characterization. The performance of this methodology is evaluated by application to a contaminated aquifer site in New South Wales, Australia, where source location, source-activity initiation time and source-flux (mass per unit time) release history are considered as unknown variables. The performance evaluation results demonstrate potential applicability of the proposed sequential methodology.
TL;DR: In this article, a modified convection-dispersion model for particle transport and deposition was developed, considering dispersive flux on the deposition kinetics, and the experimental breakthrough curves fit well with the analytical solution of the model.
Abstract: Saturated soil column experiments were conducted to determine the influences of flow direction, flow rate, and particle-size distribution characteristics on the transport and deposition of particles in saturated porous media. Two bimodal-distribution particles and one unimodal-distribution particle were employed in these studies, and soil column experiments were performed using a variety of particle-size distributions and flow conditions. In addition, a modified convection–dispersion model for particle transport and deposition was developed, considering dispersive flux on the deposition kinetics. The experimental breakthrough curves fit well with the analytical solution of the modified convection–dispersion model. Regardless of particle-size distribution, the particles’ mean velocity increases linearly with the mean interstitial fluid velocity. The particles’ mean velocity in horizontal flow is lower than that in vertical flow. Furthermore, dispersivity decreases with increasing flow rate in vertical flow. The range of the particles’ dispersivity in vertical flow is larger than that in horizontal flow. Finally, the rate of particle deposition increases with particle size. Overall, this study highlights the complicated interdependence of the effects of flow rate, flow direction, and particle-size distribution on particulate transportation and deposition.