Nitrate-N movement in groundwater from the land application of treated municipal wastewater and other sources in the Wakulla Springs springshed, Leon and Wakulla Counties, Florida, 1966-2018

Davis, J. Hal; Katz, Brian G.; Griffin, Dale W.

doi:10.3133/sir20105099

Cited by 17 publications

(47 citation statements)

References 2 publications

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“…The inland spring is simulated by the DRAIN package as the general head boundary condition in the SEAWAT model. All layers are simulated as confined aquifer since the conduit is fully saturated, which is consistent with the previous numerical models used in Davis et al (2010) and Xu et al (2015a, b) in the WKP.…”

Section: Spatial and Temporal Discretizationsupporting

confidence: 57%

“…Guo and Langevin (2002) and Werner et al (2013) pointed out that a fine-resolution vertical grid is required for accurately modeling the density-dependent flow and solute transport. The vertical thickness of each grid cell is set uniformly as 3.048 m (10 ft) in this study, significantly smaller than the large thickness of 152 m in many previous constant-density modeling studies in the WKP, for example, Davis and Katz (2007); Davis et al (2010); Xu et al (2015a, b);and Gallegos et al (2013).…”

Section: Spatial and Temporal Discretizationmentioning

confidence: 99%

“…These parameters were calibrated in the regional-scale groundwater flow and solute transport models by Davis et al (2010) and have been applied in many previous modeling studies ( Gallegos et al, 2013;Xu et al, 2015a, b). It should be pointed out that model calibration has not been conducted in this study since the head and salinity observational field data are insufficient, particularly in the conduit, considering the difficulties of monitoring devices' installation in the subsurface conduit.…”

Section: Hydrological Parametersmentioning

confidence: 99%

“…In the Ghyben-Herzberg relationship, a small rise of sea level causes extended seawater intrusion and significantly moves the mixing interface position further landward in a coastal aquifer (Werner and Simmons, 2009). For example, Essink et al (2010) systematically studied the exacerbated seawater intrusion under sea level rise and global climate change.…”

Section: Introductionmentioning

confidence: 99%

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Numerical modeling and sensitivity analysis of seawater intrusion in a dual-permeability coastal karst aquifer with conduit networks

2018

Hydrol. Earth Syst. Sci.

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Abstract. Long-distance seawater intrusion has been widely observed through the subsurface conduit system in coastal karst aquifers as a source of groundwater contaminant. In this study, seawater intrusion in a dual-permeability karst aquifer with conduit networks is studied by the two-dimensional density-dependent flow and transport SEAWAT model. Local and global sensitivity analyses are used to evaluate the impacts of boundary conditions and hydrological characteristics on modeling seawater intrusion in a karst aquifer, including hydraulic conductivity, effective porosity, specific storage, and dispersivity of the conduit network and of the porous medium. The local sensitivity analysis evaluates the parameters' sensitivities for modeling seawater intrusion, specifically in the Woodville Karst Plain (WKP). A more comprehensive interpretation of parameter sensitivities, including the nonlinear relationship between simulations and parameters, and/or parameter interactions, is addressed in the global sensitivity analysis. The conduit parameters and boundary conditions are important to the simulations in the porous medium because of the dynamical exchanges between the two systems. The sensitivity study indicates that salinity and head simulations in the karst features, such as the conduit system and submarine springs, are critical for understanding seawater intrusion in a coastal karst aquifer. The evaluation of hydraulic conductivity sensitivity in the continuum SEA-WAT model may be biased since the conduit flow velocity is not accurately calculated by Darcy's equation as a function of head difference and hydraulic conductivity. In addition, dispersivity is no longer an important parameter in an advectiondominated karst aquifer with a conduit system, compared to the sensitivity results in a porous medium aquifer. In the end, the extents of seawater intrusion are quantitatively evaluated and measured under different scenarios with the variabilities of important parameters identified from sensitivity results, including salinity at the submarine spring with rainfall recharge, sea level rise, and a longer simulation time under an extended low rainfall period.

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Section: Spatial and Temporal Discretizationsupporting

confidence: 57%

Section: Spatial and Temporal Discretizationmentioning

confidence: 99%

Section: Hydrological Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical modeling and sensitivity analysis of seawater intrusion in a dual-permeability coastal karst aquifer with conduit networks

2018

Hydrol. Earth Syst. Sci.

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“…Primjena SCPE modela u analiziranom području moguća je ako je područje istraživanja mnogo veće od reda heterogenosti geološke strukture unutar vodonosnika. Primjena SCPE pristupa pokazala se uspješnom na mjestima gdje se model mogao kalibrirati uz pomoć parametara toka i razina vode [1][2][3][4][5]. Osnovna ideja je da se ćelijama unutar modela kroz koje prolaze veće pukotine pridruže mnogo veće vrijednosti hidrauličke vodljivosti u odnosu na okolne ćelije.…”

Section: Uvodunclassified

Hydrodynamic model of groundwater flow in “Bokanjac - Poličnik” aquifer - calibration

Šreng¹,

Lončar²

2017

Zajednički Temelji 2017 - Peti Skup Mladih Istraživača Iz Područja Građevinarstva I Srodnih Tehničkih Znanosti - Zbornik Radova

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SažetakZa simulaciju toka podzemnih voda u kršu primjenjuju se razni tipovi determinističkih modela, kao što su model ekvivalentnog poroznog medija (eng. Single-Continuum Porous -Equivalent -SCPE), hibridni model (HM), diskretni model s jednom ili više pukotina. Najjednostavniji pristup od svih je primjena SCPE modela koji se bazira na pretpostavci laminarnog toka te konstantne temperature, gustoće i viskoznosti vode, gdje je tok vođen potencijalnom energijom, tj. gradijentom tlaka. Cilj ovog rada je primijeniti SCPE pristup unutar numeričkog modela Modflow kako bi se simuliralo otjecanje podzemnih voda u krškom vodonosniku "Bokanjac -Poličnik" te dobio uvid u raspodjelu ekvipotencijala i strujnog polja unutar vodonosnika. Sliv "Bokanjac -Poličnik" predstavljen je ortogonalnom mrežom s ćelijama dimenzija 200 m x 200 m u horizontalnoj ravnini te s dva sloja u vertikalnom smjeru. Kalibracija se odnosi na 29. siječnja do 30. lipnja 1967. godine (153 dana). Korišteni su podaci dnevnih oborina s ombrografske stanice smještene unutar analiziranog područja. Simulacija je pokazala da se definiranjem pukotina na način da im se pridruže velike vrijednosti koeficijenata propusnosti mogu uspješno opisati pojave unutar vodonosnika, bez upotrebe sofisticiranijih modela kao što je hibridni model (HM). Ključne riječi: krški vodonosnik, strujanje, Modflow, SCPE Hydrodynamic model of groundwater flow in "Bokanjac -Poličnik" aquifer -calibration AbstractDeterministic models such as Single -continuum porous -equivalent (SCPE), the hybrid model (HM), the discrete single fracture or pipe set model (DSFS), and the discrete multiple fracture or pipe set model (DMFS) have been used in simulating groundwater flow in karst aquifer. The simplest one, the SCPE, is based on laminar flow assumtion with constant temperature, density and viscosity of water where flow can be simulated with the potential flow equation of fluid mechanics. The goal of this paper is to apply SCPE approach within numerical model Modflow in order to simulate groundwater flow in karst aquifer "Bokanjac -Poličnik" and to get insight into spatial distribution of equipotentials and flow field. Catchment "Bokanjac -Poličnik" is represented by an orthogonal network with grid spacing of 200x200 m in horizontal plane and with two layers in vertical direction. Calibration period covers period from 29. 1.1967 to 30.6.1967 (153 days). Data from nearby ombrographic station ware used. Simulation shows that defining of karst fractures with very large hydraulic conductivity cells in an SCPE approach can successfully describe flow regime within karst aquifer.

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Development of a discrete‐continuum VDFST‐CFP numerical model for simulating seawater intrusion to a coastal karst aquifer with a conduit system

2017

Water Resources Research

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A hybrid discrete‐continuum numerical model, Variable‐Density Flow and Solute Transport—Conduit Flow Process (VDFST‐CFP), is developed to simulate seawater intrusion to a coastal karst aquifer with a conduit network. The Darcy‐Weisbach equation is applied to simulate the nonlaminar groundwater flow in the conduit system that is conceptualized as pipes, while the Darcy equation is used for laminar groundwater flow in the continuum porous medium. Density‐dependent groundwater flow with appropriate additional density terms in the conduit is analytically derived. The flow and transport equations are coupled, and numerically solved by the finite difference method with an implicit iteration procedure. Two synthetic benchmarks are developed to compare the VDFST‐CFP model results with other numerical models, such as the variable‐density SEAWAT, constant‐density continuum MODFLOW/MT3DMS, and constant‐density discrete‐continuum CFPv2/UMT3D models. The VDFST‐CFP model compares reasonably well with the other model results in both conduit and porous medium domains, and well describes water and salt exchange between the two systems. Under turbulent flow conditions within the conduit, the Darcy‐Weisbach equation calculates the flow rate more accurately without overestimation by the Darcy equation. Sensitivity analysis indicates that conduit diameter, friction factor, matrix hydraulic conductivity, and effective medium porosity are important parameters in the VDFST‐CFP model. The pros and cons of the VDFST‐CFP model are discussed, including the model assumptions and simplifications, limitations of the discrete‐continuum modeling method, and the convergence criteria. In general, the newly developed VDFST‐CFP model provides a new numerical modeling method for simulating seawater intrusion in a coastal karst aquifer with conduits.

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Nitrate-N movement in groundwater from the land application of treated municipal wastewater and other sources in the Wakulla Springs springshed, Leon and Wakulla Counties, Florida, 1966-2018

Cited by 17 publications

References 2 publications

Numerical modeling and sensitivity analysis of seawater intrusion in a dual-permeability coastal karst aquifer with conduit networks

Numerical modeling and sensitivity analysis of seawater intrusion in a dual-permeability coastal karst aquifer with conduit networks

Hydrodynamic model of groundwater flow in “Bokanjac - Poličnik” aquifer - calibration

Development of a discrete‐continuum VDFST‐CFP numerical model for simulating seawater intrusion to a coastal karst aquifer with a conduit system

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