Model-Based Analysis of the Link between Groundwater Table Rising and the Formation of Solute Plumes in a Shallow Stratified Aquifer

Groundwater table rising (GTR) represents a well-known issue that affects several urban and agricultural areas of the world. This work addresses the link between GTR and the formation of solute plumes from contaminant sources that are located in the vadose zone, and that water table rising may help mobilize with time. A case study is analyzed in the stratified pyroclastic-alluvial aquifer near Naples (Italy), which is notoriously affected by GTR. A dismissed chemical factory generated a solute plume, which was hydraulically confined by a pump-and-treat (P&T) system. Since 2011, aqueous concentrations of 1,1-dichloroethene (1,1-DCE) have been found to exceed regulatory maximum concentration levels in monitoring wells. It has been hypothesized that a 1,1-DCE source may occur as buried waste that has been flushed with time under GTR. To elucidate this hypothesis and reoptimize the P&T system, flow and transport numerical modeling analysis was developed using site-specific data. The results indicated that the formulated hypothesis is indeed plausible. The model shows that water table peaks were reached in 2011 and 2017, which agree with the 1,1-DCE concentration peaks observed in the site. The model was also able to capture the simultaneous decrease in the water table levels and concentrations between 2011 and 2014. Scenario-based analysis suggests that lowering the water table below the elevation of the hypothesized source is potentially a cost-effective strategy to reschedule the pumping rates of the P&T system.

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A New Approach in Determining the Decadal Common Trends in the Groundwater Table of the Watershed of Lake “Neusiedlersee”

Water ◽

10.3390/w13030290 ◽

2021 ◽

Vol 13 (3) ◽

pp. 290

Author(s):

Norbert Magyar ◽

István Gábor Hatvani ◽

Miklós Arató ◽

Balázs Trásy ◽

Alfred Paul Blaschke ◽

...

Keyword(s):

Water Table ◽

Water Resource Management ◽

Shallow Groundwater ◽

Groundwater Table ◽

Water Levels ◽

Driving Factors ◽

Dynamic Factor ◽

Linear Discriminant ◽

Monitoring Wells

Shallow groundwater is one of the primary sources of fresh water, providing river base-flow and root-zone soil water between precipitation events. However, with urbanization and the increase in demand for water for irrigation, shallow groundwater bodies are being endangered. In the present study, 101 hydrographs of shallow groundwater monitoring wells from the watershed of the westernmost brackish lake in Europe were examined for the years 1997–2012 using a combination of dynamic factor and cluster analyses. The aims were (i) the determination of the main driving factors of the water table, (ii) the determination of the spatial distribution and importance of these factors, and (iii) the estimation of shallow groundwater levels using the obtained model. Results indicate that the dynamic factor models were capable of accurately estimating the hydrographs (avg. mean squared error = 0.29 for standardized water levels), meaning that the two driving factors identified (evapotranspiration and precipitation) describe most of the variances of the fluctuations in water level. Both meteorological parameters correlated with an obtained dynamic factor (r = −0.41 for evapotranspiration & r = 0.76 for precipitation). The strength of these effects displayed a spatial pattern, as did the factor loadings. On this basis, the monitoring wells could be objectively distinguished into two groups using hierarchical cluster analysis and verified by linear discriminant analysis in 98% of the cases. This grouping in turn was determined to be primarily related to the elevation and the geology of the area. It can be concluded that the application of the data analysis toolset suggested herein permits a more efficient, objective, and reproducible delineation of the primary driving factors of the shallow groundwater table in the area. Additionally, it represents an effective toolset for the forecasting of water table variations, a quality which, in the view of the likelihood of further climate change to come, is a distinctive advantage. The knowledge of these factors is crucial to a better understanding of the hydrogeological processes that characterize the water table and, thus, to developing a proper water resource management strategy for the area.

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A Stationary Packer System for Layerwise Groundwater Sampling in Monitoring Wells – Technique and Results

Water Science & Technology ◽

10.2166/wst.1991.0454 ◽

1991 ◽

Vol 23 (1-3) ◽

pp. 545-553

Author(s):

M. Rödelsperger ◽

U. Rohmann ◽

F. Frimmel

Keyword(s):

Groundwater Discharge ◽

Groundwater Table ◽

Experimental Results ◽

Concentration Profiles ◽

Sampling Device ◽

Local Conditions ◽

Monitoring Wells ◽

Deep Aquifers ◽

Groundwater Sampling ◽

Groundwater Samples

A sampling device was designed as a stationary equipment for deep monitoring wells in order to obtain representative groundwater samples from different layers of the aquifer. The device consists of several packer units which can be combined at variable distances, allowing adaption to the local conditions of the aquifer and of the well. The pumps are situated below the groundwater table. Each of the drawing tubes ends between two packers at the concerning depth. Experimental results demonstrate the importance of the application of a stationary packer system instead of a mobile doublepacker in deep aquifers of inhomogeneous structure. Examples of concentration profiles obtained from layerwise groundwater sampling are given and a technique for selective groundwater discharge is described.

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The Use of Subsidence to Estimate Carbon Loss from Deforested and Drained Tropical Peatlands in Indonesia

Forests ◽

10.3390/f12060732 ◽

2021 ◽

Vol 12 (6) ◽

pp. 732

Author(s):

Gusti Z. Anshari ◽

Evi Gusmayanti ◽

Nisa Novita

Keyword(s):

Water Table ◽

Carbon Emission ◽

Bottom Layer ◽

Groundwater Table ◽

Microbial Oxidation ◽

Tropical Peat ◽

Subsidence Rate ◽

Tier 1 ◽

Tropical Peatlands ◽

Physical Changes

Drainage is a major means of the conversion of tropical peat forests into agriculture. Accordingly, drained peat becomes a large source of carbon. However, the amount of carbon (C) loss from drained peats is not simply measured. The current C loss estimate is usually based on a single proxy of the groundwater table, spatially and temporarily dynamic. The relation between groundwater table and C emission is commonly not linear because of the complex natures of heterotrophic carbon emission. Peatland drainage or lowering groundwater table provides plenty of oxygen into the upper layer of peat above the water table, where microbial activity becomes active. Consequently, lowering the water table escalates subsidence that causes physical changes of organic matter (OM) and carbon emission due to microbial oxidation. This paper reviews peat bulk density (BD), total organic carbon (TOC) content, and subsidence rate of tropical peat forest and drained peat. Data of BD, TOC, and subsidence were derived from published and unpublished sources. We found that BD is generally higher in the top surface layer in drained peat than in the undrained peat. TOC values in both drained and undrained are lower in the top and higher in the bottom layer. To estimate carbon emission from the top layer (0–50 cm) in drained peats, we use BD value 0.12 to 0.15 g cm−3, TOC value of 50%, and a 60% conservatively oxidative correction factor. The average peat subsidence is 3.9 cm yr−1. The range of subsidence rate per year is between 2 and 6 cm, which results in estimated emission between 30 and 90 t CO2e ha−1 yr−1. This estimate is comparable to those of other studies and Tier 1 emission factor of the 2013 IPCC GHG Inventory on Wetlands. We argue that subsidence is a practical approach to estimate carbon emission from drained tropical peat is more applicable than the use of groundwater table.

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Direct Push Technology and Application to Vertical Profiling of Hydraulic Conductivity in Unconsolidated Formations

9th ASME International Conference on Radioactive Waste Management and Environmental Remediation: Volumes 1, 2, and 3 ◽

10.1115/icem2003-4590 ◽

2003 ◽

Author(s):

Wesley McCall ◽

Thomas M. Christy ◽

James J. Butler

Keyword(s):

Hydraulic Conductivity ◽

Test Data ◽

Small Diameter ◽

Cost Effective ◽

Depth Interval ◽

Contaminant Migration ◽

Slug Tests ◽

Monitoring Wells ◽

Direct Push ◽

Vertical Profiling

Direct push (DP) methods provide a cost-effective alternative to conventional rotary drilling for investigations in unconsolidated formations. DP methods are commonly used for sampling soil gas, soil and groundwater; installing small-diameter monitoring wells; electrical logging; cone penetration testing; and standard penetration tests. Most recently, DP methods and equipment for vertical profiling of formation hydraulic conductivity (K) have been developed. Knowledge of the vertical and lateral variations in K is integral to understanding contaminant migration and, therefore, essential to designing an adequate and effective remediation system. DP-installed groundwater sampling tools may be used to access discrete intervals of the formation to conduct pneumatic slug tests. A small-diameter (38mm OD) single tube protected screen device allows the investigator to access one depth interval per advancement. Alternatively, a larger diameter (54mm OD) dual-tube groundwater profiling system may be used to access the formation at multiple depths during a single advancement. Once the appropriate tool is installed and developed, a pneumatic manifold is installed on the top of the DP rod string. The manifold includes the valving, regulator, and pressure gauge needed for pneumatic slug testing. A small-diameter pressure transducer is inserted via an airtight fitting in the pneumatic manifold, and a data-acquisition device connected to a laptop computer enables the slug test data to be acquired, displayed, and saved for analysis. Conventional data analysis methods can then be used to calculate the K value from the test data. A simple correction for tube diameter has been developed for slug tests in highly permeable aquifers. The pneumatic slug testing technique combined with DP-installed tools provides a cost-effective method for vertical profiling of K. Field comparison of this method to slug tests in conventional monitoring wells verified that this approach provides accurate K values. Use of this new approach can provide data on three-dimensional variations in hydraulic conductivity at a level of detail that has not previously been available. This will improve understanding of contaminant migration and the efficiency and quality of remedial system design, and ultimately, should lead to significant cost reductions.

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Seeking optimal groundwater pumping strategies at Pinggu District in Beijing, China

Journal of Hydroinformatics ◽

10.2166/hydro.2012.006 ◽

2012 ◽

Vol 15 (2) ◽

pp. 607-619 ◽

Cited By ~ 2

Author(s):

A. L. Yang ◽

G. H. Huang ◽

X. S. Qin ◽

L. Li ◽

W. Li

Keyword(s):

Groundwater Management ◽

Fuzzy Optimization ◽

Cost Effective ◽

Optimization Method ◽

Chance Constrained Programming ◽

Groundwater Pumping ◽

Simulation And Optimization ◽

Study Results ◽

Pumping Rates ◽

Beijing China

A simulation-based fuzzy optimization method (SFOM) was proposed for regional groundwater pumping management in considering uncertainties. SFOM enhanced the traditional groundwater management models by incorporating a response matrix model (RMM) into a fuzzy chance-constrained programming (FCCP) framework. RMM was used to approximate the input–output relationship between pumping actions and subsurface hydrologic responses. Due to its explicit expression, RMM could be easily embedded into an optimization model to help seek cost-effective pumping solutions. A groundwater management case in Pinggu District of Beijing, China, was used to demonstrate the method's applicability. The study results showed that the obtained system cost and pumping rates would vary significantly under different confidence levels of constraints satisfaction. The decision-makers could identify the best groundwater pumping strategy through analyzing the tradeoff between the risk of violating the related water resources conservation target and the economic benefit. Compared with traditional approaches, SFOM was particularly advantageous in linking simulation and optimization models together, and tackling uncertainties using fuzzy chance constraints.

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A delayed differentiation multiproduct model with the outsourcing of common parts, overtime strategy for end products, and quality reassurance

International Journal of Industrial Engineering Computations ◽

10.5267/j.ijiec.2021.1.001 ◽

2021 ◽

pp. 143-158 ◽

Cited By ~ 1

Author(s):

Singa Wang Chiu ◽

Victoria Chiu ◽

Ming-Hon Hwang ◽

Yuan-Shyi Peter Chiu

Keyword(s):

Cost Effective ◽

Sensitivity Analyses ◽

Optimization Approach ◽

Limited Capacity ◽

Numerical Illustration ◽

Delayed Differentiation ◽

Modeling Analysis ◽

End Products ◽

Effective Decision ◽

Effective Decision Making

Production planners today must simultaneously face with the time and quality demands of various goods externally and meet limited capacity internally. This study presents a two-stage delayed- differentiation multiproduct model that considers the outsourcing options for common parts, overtime strategy for end products, and quality reassurance to assist in making fabrication runtime decisions that are cost-effective. Stage one produces all necessary common intermediate components for end products. To reduce stage one’s utilization/uptime, this study adopts a partial outsourcing option. Stage two uses an overtime strategy to fabricate end products that further shorten the uptime. The production processes in both phases are assumed to be imperfect. This study employs the reworking/scrapping of random faulty items to reassure product quality. The researchers build a model to depict the proposed problem’s characteristics and used the mathematical modeling, analysis, and optimization approach to determine the best rotation cycle length that minimizes the system’s expenses. Further, in this study, the researchers provide sensitivity analyses and a numerical illustration, which validate the result’s applicability and exhibit its capability. This result contributes to practical multiproduct-fabrication by (1) deriving the optimal manufacturing policy for a delayed-differentiation multiproduct system with dual uptime reduction policies and quality reassurance; and (2) offering a decisional model that allows production planners to explore the collective/separate effect of a quality-ensured and dual uptime reduction strategy on a problem’s operating policy and crucial system performance indicators, which assists in cost-effective decision-making.

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Design of a hydrodynamic leachate containment system

Canadian Journal of Civil Engineering ◽

10.1139/l89-096 ◽

1989 ◽

Vol 16 (5) ◽

pp. 615-626 ◽

Cited By ~ 1

Author(s):

M. D. Haug ◽

D. J. L. Forgie ◽

S. L. Barbour

Keyword(s):

Contaminant Transport ◽

Water Table ◽

High Water ◽

Groundwater Table ◽

Cutoff Wall ◽

Transport Modelling ◽

High Water Table ◽

Cutoff Walls ◽

A Site

This paper presents the design concept for a case study sanitary landfill on a site that would not normally have been approved owing to the presence of a high water table. In this design, the base of the landfill was intentionally placed below the water table. A massive 2.5 m wide, 2.5 m high cutoff wall and a 0.3 m thick liner with hydraulic conductivities of approximately 5 × 10−10 m/s were constructed of recompacted glacial till to limit both groundwater intrusion into the landfill and leachate migration out of the landfill. In this case study, the landfill base was placed below the water table to (i) provide a relatively inexpensive source of cover material and (ii) use the hydrodynamic gradient from the high water table to help contain the leachate. Finite element modelling of the seepage and contaminant transport, for alternate designs for lined and unlined landfills placed above and below the groundwater table, is shown to confirm a previous, less-sophisticated, estimation that placing a lined landfill below the groundwater table has definite advantages in reducing both leachate seepage and contaminant transport. Key words: landfill, leachate, hydrodynamic containment, liners, compacted earth cutoff walls, seepage and contaminant transport modelling.

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CONTAINMENT AND REMOVAL OF FUEL OIL FROM GROUNDWATER BENEATH A DENSELY POPULATED HOUSING DEVELOPMENT

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1985-1-267 ◽

1985 ◽

Vol 1985 (1) ◽

pp. 267-271 ◽

Cited By ~ 2

Author(s):

Joseph T. McNally ◽

Craig G. Robertson ◽

Ned E. Wehler

Keyword(s):

Water Table ◽

Product Recovery ◽

Water Levels ◽

Housing Development ◽

Fuel Oil ◽

Monitoring Wells ◽

Irrigation Pond ◽

New Castle County ◽

Periodic Monitoring ◽

Product Thickness

ABSTRACT A leak from a buried pipeline resulted in the loss of approximately 30,000 gallons of No. 2 fuel oil beneath a housing development in suburban New Castle County, Delaware. After seeping to the water table, the resultant hydrocarbon plume threatened the homes as well as a downgradient stream and an irrigation pond. Site geology consisted of a highly-weathered metamorphic rock overlain by varying thicknesses of fill material. A steep water table gradient existed; the depth to the water table ranged between 6 and 17 feet below grade. Two-inch monitoring wells were installed in public easements and the back yards of private residences. The extent of the oil plume was determined by measuring product thicknesses, which ranged from a few inches to over 5 feet, in monitoring wells. To establish hydrodynamic control and prevent further migration of the plume, two eight-inch recovery wells were drilled and configured with water-table depression pumps. For product recovery, Auto-Skimmers were selected because of the variable water levels and need to leave no measurable product thickness in the wells. The potential for product recovery in other parts of the site was determined by performing unattended one-week recovery tests in the two-inch monitoring wells under non-pumping conditions using an Auto-Skimmer. Based on these results, three additional six-inch recovery wells were drilled. The recovery operation successfully halted the advancement of the contaminant plume and protected the downgradient stream and irrigation pond. In addition, more than 3,000 gallons of fuel oil were recovered from the subsurface. After 18 months, the recovery equipment was removed and only periodic monitoring of the monitoring wells was required.

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IDENTIFICATION AND INITIAL RECOVERY OF JET A FUEL FROM THE GROUND UNDERLYING A TANK FARM AT PALM BEACH INTERNATIONAL AIRPORT

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1985-1-277 ◽

1985 ◽

Vol 1985 (1) ◽

pp. 277-283

Author(s):

Kenneth M. Ries

Keyword(s):

Water Table ◽

Fine Sand ◽

The State ◽

State Agency ◽

Monitoring Wells ◽

Monitoring Well ◽

Tank Farm ◽

Product Flow ◽

Water Pumping ◽

Initial Recovery

ABSTRACT A recent surface fuel spill incident by tank overflow at a 220,000 gal above-ground airport tank farm led to a single monitoring well installed at the request of the state. This well disclosed previously spilled Jet A fuel at the water table, 5 ft below grade. Eight monitoring wells averaging 7 ft deep were completed in 3 days, revealing a surprisingly confined pool of fuel in fine sand estimated at 24,000 ft2 but with over 30 in. of fuel in some wells. Monitoring wells 40 ft away showed a complete absence of fuel. Leaking from underground piping was tested and eliminated as a possible source. Above-ground spills, it was concluded, were insufficient as a source. Inventory records failed to show any losses. Gas chromatic analysis of the product confirmed that it was Jet A, and therefore not JP-4 from an abandoned Air Force fuel main. The source of fuel was concluded as primarily from the practice of daily fuel tank sumping to the ground, which ceased in 1974. Significantly, the spill was 10 years old and had not moved. Initial recovery was by slotted drum, later replaced by a 70 ft by 3 ft trench to the water table, gravel backfilled. Recovery of product only, without water pumping, was by an electrical chemical metering pump, continuously, at the rate of product flow to the trench, averaging 23 gal per day. Investigations of groundwater quality in nearby monitoring wells by the state agency failed to show any hydrocarbons, analyzed down to 5 parts per billion. The closest water well, 1,800 ft away, showed no contamination. Bench scale testing demonstrated that monitoring well fuel thickness overstates fuel thickness in the ground, and that trenches concentrate fuel thicknesses like monitoring wells. Tight cost control was maintained, with monitoring wells costing under $50 each, a recovery trench under $2,000, and recovery pumping under $1,000. By-product recovery revenue has offset some recovery costs.

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Evaluation of three global gradient-based groundwater models in the Mediterranean region

10.5194/egusphere-egu2020-8237 ◽

2020 ◽

Author(s):

Nahed Ben-Salem ◽

Alexander Wachholz ◽

Michael Rode ◽

Dietrich Borchardt ◽

Seifeddine Jomaa

Keyword(s):

Water Table ◽

Mediterranean Region ◽

Global Scale ◽

Groundwater Table ◽

Groundwater Depletion ◽

Groundwater Model ◽

Anthropogenic Pressures ◽

Groundwater Levels ◽

Gradient Based ◽

The Mediterranean

The Mediterranean region is recognized as one of the most sensitive regions in the world to water scarcity, due to both climate change and consistently increasing anthropogenic pressures. Groundwater is considered as a strategic freshwater reserve in the Mediterranean region; however, its status remains poorly characterized and its total budget uncertain. In recent years, groundwater modelling has moved from local to regional/global scale, offering insights into the status of data-scarce regions. However, it remains unclear to what extent those models can be used to support management decisions. This study aims to compare and evaluate the performance of three groundwater models to represent the steady-state groundwater levels in the Mediterranean region. Thus, the groundwater models of Reinecke et al. (2019), de Graaf et al. (2017) and Fan et al. (2013) will be utilized in this study. The preliminary results indicate that, in the northern part of the Mediterranean region, the models of Reinecke et al. (2019) and de Graaf et al. (2017) predict similar water table patterns. However, both models simulate completely different groundwater regimes in the desert regions; the predicted groundwater table of de Graaf et al. (2017) model is significantly deeper than of Reinecke et al. (2019) model. This could be, probably, because of the calibration of de Graaf et al. (2017) model compared to Reinecke et al. (2019) model, which is not yet calibrated. A detailed comparison between simulated and measured water table depth of different Mediterranean aquifers having different climatic, geologic and anthropogenic conditions will be presented.ReferencesReinecke, R. et al. Challenges in developing a global gradient-based groundwater model (G3M v1.0) for the integration into a global hydrological model. Geosci. Model Dev 12, 2401-2418 (2019).de Graaf, I. et al. A global-scale two-layer transient groundwater model: Development and application to groundwater depletion. Adv. Water Resour 102, 53-67 (2017).Fan, Y. et al. Global patterns of groundwater table depth. Science 339, 940-943 (2013).&#160;

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