Assessment and Prediction of Groundwater Quality using Hydrochemical, Flow and Transport Modeling in the Kolhar Industrial Area, Bidar District, Karnataka, India

Groundwater samples for pre and post-monsoon seasons were collected from the watershed covering Kolhar Industrial Area (KIA), Bidar District, Karnataka for assessment of groundwater quality and its possible contaminant migration from the industrial area. Major ions and heavy metal chemistry was analyses for collected samples. Groundwater samples from industrial area shows elevated Total Dissolved Solids (TDS) concentration than groundwater samples from the other part of the watershed. Based on groundwater quality analyses results, four high TDS concentrations zones of 2000 to 8000 mg/l were identified in an industrial area wells. Groundwater flow and transport modeling was carried out to decipher the possible migration pathways and direction of contaminant migration. Groundwater flow and transport modeling suggests that the high TDS concentration were follows general topographic level trend of contaminant migration. The groundwater transport model was calibrated for fifty years. The modeling study also suggests that the different high TDS concentration plumes were joins together after fifty years. Keywords: Kolhar Industrial Area (KIA), Total Dissolved Solids (TDS), Flow and Contaminant transport modelling

Using Multiple Environmental Tracers to Estimate Field-Scale Longitudinal Dispersivity

In this study, we seek to reduce parameter uncertainty in groundwater modeling systems, particularly in reactive transport models, by quantifying effective field-scale longitudinal dispersivity using anthropogenic environmental tracers. We generate synthetic aquifer fields and model transport of atmospheric tracers and test whether tracers can be used to determine an effective aquifer-scale dispersion coefficient. We generate synthetic datasets by simulating transport of chlorofluorocarbons (CFC11, CFC12, CFC113), sulfur-hexafluoride (SF6) and tritium (3H) with input functions derived from known atmospheric concentrations, through a three-dimensional, stochastic, heterogeneous synthetic aquifer developed using sequential Gaussian simulation using the PFLOTRAN reactive transport model. Flux-averaged concentrations calculated from model output are used as synthetic observation datasets to calibrate effective dispersivity for simplified homogeneous models with the PEST parameter estimation software. Tracer-derived effective dispersivity values are compared with theoretical and empirical values reasonable for our stochastic structure. We assess the ability of our homogenous model with tracer-derived effective dispersion coefficients to reproduce transport of a synthetic contaminant through the heterogeneous 3D field with two new boundary conditions. The ratio of CFC11/SF6 displays less than a 10% difference between the full (4.12m) and single-time (4.43m) series derived effective dispersivity. The ratio of CFC12/SF6 displays less than a 10% difference between the full (4.09m) and single-time (4.43m) series value. While all tracer-derived values from both the full-time and single-time series (1.96 m to 10.75 m) were within reason compared to the theoretically and empirically derived values (1.01 m to 5.32 m), dispersivity values derived from CFC11/SF6 and CFC12/SF6 for the full and single-time series display quantitatively smaller residuals compared to our heterogeneous truth model for our new boundary conditions. Our results indicate that environmental tracers can be useful in estimating effective dispersion coefficients for reactive transport models over longer length and time scales than traditional applied tracer studies. This new method of utilizing multiple environmental tracers over a limited time series could be an easy, inexpensive, and effective solution in quantifying field-scale longitudinal dispersivity and reduce parameter uncertainty in groundwater/contamination transport models

Parameterization of modeling subsurface hydrocarbon contamination and biosurfactant enhanced remediation processes

Subsurface hydrocarbon contamination caused by accidental spills or operational leakages of petroleum products is a global environmental concern. In order to cost-effectively and eco-friendly recover the contaminated sites, biosurfactant enhanced aquifer remediation (BSEAR) technologies have become a popular subject in both research and practice. However, the inherent uncertainties and complexities of the subsurface systems make it challenging in numerical simulation of the hydrocarbon transport and fate as well as remediation processes. Efforts in developing more efficient and robust parameterization approaches for such modeling purpose, therefore, are highly desired. This research aims to help fill the gap by developing a novel hybrid stochastic – design of experiment aided parameterization (HSDP) method for modeling BSEAR processes. The method was developed and tested based on an integrated physical and numerical modeling system comprised of a set of intermediate scale flow cells (ISFCs) and a numerical simulator named BioF&T 3D. Generally, the HSDP method was performed by: 1) building the design of experiment (DOE) models based on screened parameters and defined responses, which could reflect the goodness of fit between observed and simulated data; 2) identifying the and interactions among parameters and their significance; 3) optimizing the DOE predicted responses; 4) introducing stochastic data within reduced intervals based on the optimized parameters; 5) running Monte Carlo simulation to find the optimal responses with the corresponding combinations of parameters. The flow cell tests proved that the HSDP method could improve both efficiency and robustness of modeling parameterization and significantly reduce the computational demand without compromising the effectiveness in quantifying parameter interactions and uncertainties. Furthermore, a specific lab synthetized surfactin was applied in this study. The effect of dissolution enhancement was observed from parallel flow cell experiments especially during the first 12 hours following the initial hydrocarbon release. The HSDP method was demonstrated to be capable of advancing BioF&T 3D, which lacks the capacity of simulating surfactant. By incorporating the HSDP method, the BSEAR processes were effectively simulated with a satisfactory overall goodness of fit (R² = 0.76, 0.81, 0.83, and 0.81 for benzene, toluene, ethylbenzene, and xylene, respectively). The enhanced dissolution effect was also reflected in the modeling parameterization by increasing the first 12 hours hydrocarbon loading ratio (12LR) compared to non-biosurfactant processes. This research developed a new parameterization method HSDP, which is capable of revealing interactions of parameters, as well as quantifying their uncertainties, in a robust and efficient manner. Also, using this method, this study initiated the attempts to advance simpler numerical models in simulating complicated BSEAR processes, which is particularly attractive for the potential applications in practice

Modelación hidráulica y de calidad del agua acoplada para humedales, mediante Processing Modflow

Considerando que se deben incluir los factores hidráulicos y las condiciones ambientales para la simulación de humedales (Kadlec, 2.000, Wynn and Liehr, 2.001) en este trabajo se realizó la aproximación a la modelación de flujo, transporte y reacción de contaminantes a través del ajuste de los paquetes computacionales MODFLOW y MT3DMS incluidos en el software Processing Modflow, desarrollados originalmente para su uso en aguas subterráneas, que aunque no realizan la modelación acoplada, se integran entre sí permitiendo conocer el funcionamiento y dinámica de un humedal. La información base utilizada para el modelo, correspondió a la topografía y conformación del humedal, datos de cabezas hidráulicas en seis puntos de medición, resultados de monitoreos de calidad del agua en cuanto a concentraciones de Demanda Bioquímica de Oxígeno (DBO5), Nitrógeno Total Kjeldahl (NTK) y Fósforo Total (PT), datos teóricos de porosidad, coeficientes de difusión, dispersión y degradación de contaminantes, e información climatológica con el fin de incluir los efectos de recarga (por precipitación) y evapotranspiración.In order to model the spatial behavior of wetlands, this work presents the modeling of flow and transport of contaminants in the third upper zone of the Jaboque wetland, which is located in the city of Bogotá The simulation was done through the use of the finite difference based software Processing Modflow, which was adjusted for the modeling of wetlands, by using the equations of flow in porous media flow and transportoThese equations are solved by the computer packages MODLFOW (hydraulic model) and MT3DMS (transport model) respectively through steady-state simulations, included in the simulator. Results of the modeling showed that the most sensitive parameters correspond to the hydraulic conductivity for flow model, and the first order kinetic degradation rates for the Biochemical Oxygen Demand (BOD5), the Total Kjeldahl Nitrogen (TKN), and Total Phosphorous (TP). Based on the calculated parameters, the model shows the spatial distribution of hydraulic heads calculated and the concentration of the pollutants evaluated correspond with the real situation of the wetland.Magíster en HidrosistemasMaestrí

HST3D; a Computer Code for Simulation of Heat and Solute Transport in Three-dimensional Ground-water Flow Systems

The Heat- and Soil-Transport Program (HST3D) simulates groundwater flow and associated heat and solute transport in three dimensions. The three governing equations are coupled through the interstitial pore velocity, the dependence of the fluid density on pressure, temperature, the solute-mass fraction , and the dependence of the fluid viscosity on temperature and solute-mass fraction. The solute transport equation is for only a single, solute species with possible linear equilibrium sorption and linear decay. Finite difference techniques are used to discretize the governing equations using a point-distributed grid. The flow-, heat- and solute-transport equations are solved , in turn, after a particle Gauss-reduction scheme is used to modify them. The modified equations are more tightly coupled and have better stability for the numerical solutions. The basic source-sink term represents wells. A complex well flow model may be used to simulate specified flow rate and pressure conditions at the land surface or within the aquifer, with or without pressure and flow rate constraints. Boundary condition types offered include specified value, specified flux, leakage, heat conduction, and approximate free surface, and two types of aquifer influence functions. All boundary conditions can be functions of time. Two techniques are available for solution of the finite difference matrix equations. One technique is a direct-elimination solver, using equations reordered by alternating diagonal planes. The other technique is an iterative solver, using two-line successive over-relaxation. A restart option is available for storing intermediate results and restarting the simulation at an intermediate time with modified boundary conditions. This feature also can be used as protection against computer system failure. Data input and output may be in metric (SI) units or inch-pound units. Output may include tables of dependent variables and parameters, zoned-contour maps, and plots of the dependent variables versus time. (Lantz-PTT

Groundwater age in the Wairarapa

This dissertation focuses on the catchment-scale evaluation of groundwater age as a function of space and time in the 270 km² Middle Wairarapa catchment. The simulation of the mean age and point distribution of ages, contributing to a regional age estimate, is a novel demonstration of the recently developed groundwater software, Cornaton (2012). The Wairarapa is in the southern North Island of New Zealand and is a dynamic water catchment exhibiting complex interactions between its rivers and shallow aquifers. Groundwater has been widely utilized since the 1980s for agriculture, horticulture and drinking water; increasing land use development (i.e. irrigation and nutrient application) requires effective regional management of both the quantity and quality of water resources. Groundwater age provides insights into groundwater flow and transport processes and thus enables better management of groundwater resources. Subsurface water age information enables the interpretation of recharge influence, zones of sensitivity for sustainable abstraction, as well as contamination risk from land-use intensification to drinking water supplies. It is accepted that groundwater is composed of a mixture of water with different ages, however, until very recently mean age has been the primary indicator for groundwater age assessment. Mean age alone can misrepresent the potential for contamination from young water; for example, a groundwater sample with an old mean age may still contain a significant fraction of young water; therefore, a fuller understanding of the age distribution in both time and space is important for groundwater management. The ability to simulate the full distribution of groundwater age within transient numerical groundwater models has only been very recently enabled, through implementation of the time-marching Laplace transform Galerkin technique (TMLTGT), and is demonstrated in this dissertation. A transient finite-element groundwater flow model originally developed by Greater Wellington Regional Council was converted to simulate transport of the age tracer tritium and groundwater age using the Ground Water (GW) software. Observed tritium concentrations were utilized in the calibration using the Monte Carlo and Gauss-Marquardt-Levenberg methods. Following the calibration of the transport model the GW software was then used to derive pumping well capture zones and directly simulate age throughout the Middle Wairarapa Valley catchment. The advective dispersive equation and the TMLTGT were used for transient mean-age and transient simulations of the full distribution of groundwater age. The results are presented as maps and graphs of both mean age and age distributions throughout the Middle Valley, covering a 15 year simulation period. The mean-age simulations indicated the groundwater age in the valley was strongly influenced by seasonal changes and extreme climatic events. Significant variations existed, from high rainfall recharge percolating young water throughout the domain, to dry extended droughts limiting recharge and increasing the age throughout large sections of the Middle Valley. Age distributions were shown to be strongly influenced by abstraction pressures, depth and geology. Abstractions were shown to skew the age distribution, creating both older and younger mean-ages depending on the location of the observation point, and several simulations indicated the potential misrepresentation of young (potentially contaminated) water quantified as old by mean-age assessment. These results show the dynamic nature of the Middle Valley groundwater system and its inherent vulnerabilities. The Wairarapa transient age distributions are one of the first such examples in New Zealand, and they demonstrate the potential of the information interpreted from age estimates to more effectively manage groundwater resources