Meghan Magill
Abstract
Two papers regarding modeling in contaminant transport were examined. Numerical
modeling of immiscible organic transport at the Hyde Park Landfill (Osborne and Sykes,
1986) utilized numerical modeling to estimate NAPL migration. A two-dimensional
finite element model was developed to simulate immiscible organic transport in
groundwater. The model used coupled, second-order, nonlinear partial differential
equations documented in petroleum industry literature. The model was verified by a onedimensional finite difference two-phase flow simulator and ground-truthed through a
field study of the Hyde Park Landfill in New York. The model was found to consistently
underestimate the extent of NAPL migration. The second paper, Dissolution of dense
chlorinated solvents into groundwater. 3. Modeling contaminant plumes from fingers and
pools of solvent (Anderson et al., 1992) utilized analytical modeling to estimate
chlorinated hydrocarbon (CHC) transport and dissolution. Two analytical solutions to the
three-dimensional advection-dispersion equation, along with lab-determined mass
transfer rates, were used to model dispersion and concentrations of CHC in different
configurations of fingers and pools. The study concluded that fingers of CHC dissolve
and move through the system fairly quickly, while pools of CHC are a source of longterm contamination.
Anderson, M.R., Johnson, R.L., and Pankow, J.F., 1992, Dissolution of dense chlorinated
solvents into groundwater. 3. Modeling contaminant plumes from fingers and
pools of solvent: Environmental Science Technology, v. 26, p.901-908.
Osborne, M. and Sykes, J., 1986, Numerical modeling of immiscible organic transport at
the Hyde Park Landfill: Water Resources Research, v. 22, p. 25-33.
Wenming Nie
Vrugt J.A., Stauffer P.H., Wohling Th., Robinson B.A., and Vesselinvo V.V. 2008
Inverse modeling of subsurface flow and transport properties: A Review with new
developments. Vadose Zone J. 7: 843-864.
Inverse modeling is the only method to derive some soil hydraulic properties in
groundwater flow and transport at relatively large scales, which can not be directly
measured by laboratory experiments. Inverse modeling refers to the process of parameter
iterative adjusting, in order to minimize the error of model approximation relative to the
responding observation under study during a period of time. The inverse modeling
method used to estimate parameters in unsaturated flow and transport processes has been
reviewed, including how the inverse modeling works, the historical research background,
and numerical solution used to deal with the property estimation problems. Three case
studies are provided to illustrate recent developed methods, including “multi-method
global optimization, parallel computing, and sequential data assimilation”, which are
used to enhance efficiency of property estimation and output assessment. The first case
study is a “global optimization of a three dimensional soil vapor extraction model” used
to estimate content of subsurface volatile organic compounds close to the “Los Alamos
National Laboratory”. In the second case study, field measuring tesionmetric pressure
data in New Zealand are utilized to calibrate unsaturated soil hydraulic parameters by
“multiobjective calibration” method. In the third case study, data collected from a “multitracer experiment” at Yucca Mountain, NV, are used for soil hydraulic property and state
estimation in “a groundwater solute mixture model” at relatively large scale.
Achyut Adhikari
Reference Paper:
Sharda, V.N., R.S. Kurothe, D.R. Sena, V.C. Pande and S.P. Tiwari, 2006 Estimation of
groundwater recharge from water storage structures in semi-arid climate of India. Journal
of Hydrology 329, 224-243
Groundwater is an important source of irrigation in India accounting for more than half of
the net irrigated area in the country which also contribute 70-80% of the total agriculture
production. Ground water exploitation beyond recharge capacity is the major reason
behind the sharp decline of water table. Analysis of water table fluctuations (WTF) is
useful tool for determining the magnitude of both short and long term changes in
groundwater recharge and has been widely applied under varying climatic conditions.
Groundwater recharge from water storage structure under semi-arid conditions of western
India has been estimated by employing water table fluctuation and chloride mass balance
(CMB) methods. An attempt has been made to analyze the multidisciplinary perspective
of ground water-surface water interaction in the context of water storage structures in two
adjacent micro-watersheds. Average recharge per annum was found to be similar while
using both methods in the same area. A diagnostic relationship correlating the rainfall to
the potential recharge from water storage structures has been developed to explain the
characteristics of the storage structures for a given geographical location.
The study has revealed that a minimum of 104.3 mm cumulative rainfall is required to
generate 1mm of recharge from the water storage structures. Further, critical appraisal of
this relationship indicated that individual storage structure in the watershed has a limiting
capacity to induce a maximum recharge irrespective of the amount of rainfall. The
maximum potential recharge from a structure can be achieved at a rainfall lower than the
existing average rainfall in a given area. This findings is expected to be helpful on
designing the storage structure more efficiently for inducing ground water recharge and
can serve as a parameter to compare the water harvesting structures in a given agroecological situation.
The Chloride mass balance (CBM) method was used to assess its efficiency in estimating
the annual recharge in comparison to WTF method. Both methods were found to yield
comparable results for estimation of actual groundwater recharge. The storativity
estimated by the water balance approach was in conformity with the recharge estimates
of CMB method and can be used as a weighted parameter representing the whole
watershed. An empirical linear relationship was found to reasonably correlate the changes
in chloride concentration with water table rise or fall in the study area.
Jeremy Koonce
ABSTRACT
Groundwater flow and contaminant transport through the vadose zone is important to
agricultural water management and the environment. Due to the complexity of flow
through the unsaturated zone, numerical models are used extensively to determine
hydraulic properties. In this paper, hydraulic parameters were obtained from upward
flow experiments by combining numerical flow models and parameter estimation. The
flow experiment was conducted using inverse modeling to determine the hydraulic
properties of a silty clay in a 4 m long, 2 m wide, and 3 m deep weighing lysimeter
combined with parameter optimization (parameter uniqueness) using the Hydrus model
and sensitivity analysis (van Genuchten-Mualem). Hypothetical flow variables from the
Hydrus 1D model, including pressure head, volumetric water content, and upward flow,
were most sensitive to pore-size distribution index and least sensitive to residual
volumetric water content and pore-connectivity. Holding residual volumetric water
content and pore-connectivity in the Levenberg-Marquardt non-linear minimization
method (inverse model procedure in Hydrus 1D) provided the best optimization. The
results were then applied to the groundwater table lysimeter. Volumetric water content
from capacitance sensors and multiple initial parameter estimates were used to determine
hydraulic properties for two locations in the lysimeter. Volumetric water content values,
both calculated and measured, correlated well; however, rates at which water content
increased were generally overestimated. These results can be used to study capillary rise
from the groundwater table.
Joseph Asante
Article: Zume, J., and Tarhule, A., (2008), Simulating the impacts of groundwater
pumping on stream-aquifer dynamics in semiarid northwestern Oklahoma, USA: Journal
of Hydrogeology, v.16, p.797-810
Abstract
MODFLOW, the numerical modeling technique was used to evaluate the impacts of the
anthropogenic withdrawals of groundwater on streamflow in the Alluvium and Terrace
(A/T) aquifer of the Beaver-North Canadian River (BNCR) in northwestern Oklahoma,
USA. Specifically, the simulation was used to estimate pumping induced streamflow
depletion resulting from reduced baseflow and increased stream leakage. Simulating the
A/T aquifer-streamflow interaction was necessary because the A/T aquifer and surface
water face competing uses from agricultural, industrial, aquatic and wetland ecosystems.
The model was developed from the geologic information and hydrologic information
including well completion reports and logs. Leakages into neighboring basins as well as
spring discharges were simulated using drain package. Stream—aquifer interaction was
also simulated with streamflow routing package (SFR1). Model was calibrated to both
quasi-steady state and transient state by matching simulated and measured groundwater
levels and flows. Calibrated parameters are the hydraulic conductivity, recharge, specific
storage, streambed and drain conductances, and mannings roughness coefficient. The
simulated results show that the baseflow contributes 56 % of the total the streamflow,
while the stream leakage also contributes 30% of total aquifer recharge. The model
results are important for evaluating alternative decisions to ensure sustainable use and
management of water stressed semiarid regions.
Jeevan Jayakody
Coupled surface and ground water models for investigating hydrological processes
Abstract
This paper describes about coupled surface and groundwater models to simulate rainfall –
runoff process in Shihmen reservoir watershed, Taiwan. The watershed model is
composed of several modules to integrate overland flow, stream flow, unsaturated and
saturated flows in unconfined aquifers and saturated flow in confined aquifers.
Percolation, infiltration, surface runoff, groundwater flow and evaporation are
mathematically simulated in the model. The model parameters were determined from
calibration and several case studies. In general, hydrographs of simulated and observed
runoff values are in a good agreement for both short-duration (few days) and long
duration (few weeks) simulations but there are significant differences in peak values.
Original Paper:
Coupled surface and ground water models for investigating hydrological processes
Ray-Shyan Wu, Dong-Sin Shih, Ming-Hsu Li and Chia-Ching Niu
Hydrological Process. 22, 1216–1229 (2008)
Yiping Li
Impacts of the Yangtze River water transfer on the restoration of Lake Taihu, China
Weiping Hua,∗, Shuijing Zhaia,b, Zecong Zhua,b, Hongjuan Hana,b
a State Key Laboratory of Lake Science and Environment, Nanjing Institute of
Geography and Limnology,
Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China
b Graduate School of Chinese Academy of Sciences, Beijing, China
Abstract:
Lake Taihu is the third largest freshwater lake in China, with a water surface area of
2338km2. With the economic and social development and the population increase, more
pollutants have been discharged into Lake Taihu, resulting in water pollution and
eutrophication in the lake. In order to improve the water quality and to abate the jeopardy
of water bloom in Lake Taihu, China, two experimental water transfers from the Yangtze
River to Lake Taihu were conducted in winter–spring 2002 and in summer–autumn 2003.
The water transfer route is shown in Fig. 1. In this study, an ecological model (EcoTaihu)
was introduced to assess their environmental effects. First, the model was re-calibrated
and reverified for the periods of the water transfer, then numerical calculations with and
without the water transfer were carried out. The percentage of the area where water
quality was improved by the water transfer was calculated in seven sub-zones of the lake.
The results show that the experimental water transfers in both of the periods have notable
positive effects on debasing the concentration of phytoplankton, total nitrogen and
dissolved oxygen in some sub-areas. The positive effects fluctuated with the duration of
the water transfer, and were different for different water quality parameters and in
different sub-zones. Among the five water quality parameters considered, chlorophyll a
achieved the most significant improvement. There are no notable positive effects on the
total phosphorus in any sub-zones. Meiliang Bay, Gonghu Bay and Northwest Zone had
more positive effects than the east epigeal zone and Dongtaihu Bay. As the water transfer
results in net input of nitrogen and phosphorus to Lake Taihu, it can only be used as an
emergency measure to abate the jeopardy resulting from water bloom. Otherwise, the
water transfer would increase the risk of eutrophication in Lake Taihu if the
concentration of phosphorus and nitrogen in the influent water was not cut down to a
reasonable level.
Keywords: Water transfers，Restoration，EcoTaihu model，Yangtze River，Lake
Taihu
Lisa Hancock
ARGE-SCALE, PROCESS-BASED GROUNDWATER FLOW MODELS VRS
SMALL-SCALE, PHYSICALLY-BASED MODELS; MAKING BOTH WORK WHEN
DETERMING INTERACTION BETWEEN GROUND AND SURFACE WATERS.
Groundwater models have revolutionized how we look at water resource management.
Yet no one model that can do it all; interaction between local (small-scale) and regional
(large-scale) and their integration with the hydrogeologic cycle. Different groundwater
models deal with different scales; large-complex integrated models for regional systems
and process-based/finite-difference models for local systems. Attempts have been made
to take regional size systems and integrate them with small-scale numerical models; once
such attempt was with the Upper Danube Basin, which is in Germany, Austria, and
Switzerland. It is a mountainous catchment (water supplier) with a hilly foreland (water
consumer) ranging in elevation from 300 to 3600 meters above sea level. The Ammer
subcatchment was also used due to it having typical hydrogeometric characteristics
similar to the Upper Danube. The Ammer subcatchment is located at the transition zone
of the Alps and their foreland. A complex model with high temporal resolution (coarsely
discretized 1000 x 1000m grid size) was run for the Upper Danube while two numerical
models (finely discretized 100 x 100m and coarsely discretized 1000 x 1000m) of the
alluvial aquifers in the Ammer subcatchment were developed. A model was also run that
incorporate the 100 x 100 meter cell of the Ammer model into the 1000 x 1000m cell of
the Upper Danube model. The main focus of the models was the aspects relevant to the
discretization of the alluvial aquifers in both catchments and to compare the finely
discretized model with the coarsely discretized one.
Although considered unconfined by the models, a minimum thickness of the alluvial
aquifers was defined in order to prevent grid cells from falling dry. The alluvial aquifers
were small in comparison to the coarse 1000 x 1000m grid size. This problem was
solved by adding cells to the grid so that a closed-system for groundwater flow using a
finite-difference scheme could be achieved. A neighboring cell was added to each
aquifer cell in the direction of groundwater flow. The Hydrogeologic Catchment
Drainage Analysis was applied to the models to ensure hydraulic conductivity (Collins
1975, Fairfield 1991). This analysis changes land surface such that every cell has a
defined flow direction, which results in the surface water being routed to a catchment’s
lowest point. This also fixes any aquifer bottom “peaks” that might have popped up. A
land surface analysis was then completed by using the TOPAZ model (Garbrecht and
Martz 1995). After each model was run, they were compared to one another. Twenty
different zones within the Ammer subcatchment were used to perform a steady-state
simulation for the finely descretized model. These results were then used as initial
conditions for transient model runs. MODFLOW calculated the groundwater flux from
aquifers to rivers, which was used as the base flow component in the corresponding
hydrological catchment models that use routing algorithms for discharge modeling in the
rivers. Calibration ensures a good fit between the model results and the mean values of
observed data.
Using the power of averaging, the coarsely discretized Ammer model showed the best fit
of computed groundwater levels compared to measured data. Groundwater discharge in
the Ammer catchment from groundwater to rivers was evaluated; for the 100-m model
exfiltration was 12.7 m3/s and for the 1000-m model exfiltration was 13.1 m3/s.
Groundwater components contributes approximately 60% to discharge. A comparison
between the fine and coarse model show a small discrepancy (0.4 m3/s), which confirms
the applicability of the coarse model for this application.
Xiang Long
Modeling coupled water flow, solute transport and geochemical reactions affecting heavy
metal migration in a podzol soil
D. Jacques, J. Šimůnek, D. Mallants and M.Th. van Genuchten
Coupled models are useful to understand the impact of natural processes and
antropogenic activities on soil evolution based on Process-based models which integrate
these various processes, such as water flow, multicomponent solute transport, heat
transport and biogeochemical processes and reactions. In this paper, HYDRUS-1D and
PHREEQC-2 were weak coupled and designed to address multicomponent geochemical
transport processes in the vadose zone. 30 years’ transient flow and heavy metal
movement in soil profile were simulated by linking the transport of solute and major
cation exchange. The results show water moisture and water fluxes can significantly
control the mobility and availability of heavy metals. Near the soil surface, decreasing
water moisture made the PH low and new ion exchange equilibrium. Higher aqueous Cd
concentration was found near the surface because the upward transport and accumulation
of Cd-Cl was driven by increased evapotranspiration. Coupled (HP) model can simulate
the complex interaction between soil physical and biogeochemical processes and the
approaches are available.