Groundwater modelling (an Introduction)

By : Putika Ashfar K
Groundwater Modelling
( Introduction)

References :
 Gang Ji, Zen.2008. Hydrodynamics and Water Quality: Modeling
Rivers, Lakes, and Estuaries. John Wiley & Sons, Inc.,
 Kumar, C.P. 2013 Numerical modelling of ground water flow
using MODFLOW,Indian Journal of Science. 2(4). 86-92,
 O. Lehn Franke, Thomas E. Reilly, and Gordon D. 1987. Bennett
Definition of Boundary and Initial Conditions in the Analysis of
Saturated Ground-Water Flow Systems – An Introduction. USGS
- TWRI Chapter B5, Book 3,
 Khadari, S.F.F., Pande, Chaitanya. 2016. Ground water flow
modeling for calibrating steady state using MODFLOW software:
a case study of Mahesh River basin, India.Model. Earth Syst.
Environ. 2(39)
 Winston, Richard B., Voss, Clifford I., 2004. SutraGUI - A
Graphical User Interface for SUTRA, A Model for Ground-Water
Flow with Solute or Energy Transport. USGS

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
1. Groundwater modeling is an important
component in water resources system
2. With increasing of groundwater withdrawal,
the groundwater qualiity has been continously
deteriorating

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Typically groundwater modeling purposes :
1. To know aquifer properties
2. To know aquifer characteristics
3. Stimulate the response of the aquifer
4. Identify recharge-discharge area
5. Identify groundwater levels

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
General Data Needs
1.Topographics
http://eros.usgs.gov/elevation-products
2. Water Elevation

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
General Data Needs
3. Geological Information
http://landsat.usgs.gov//metadatalist.php
4. Hydrogeologic Properties (maps of K, T distributions)

Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
3. Climate data (rainfall, evaporation, precipitation,
temperature)
https://pmm.nasa.gov/TRMM
4. Land use (LU)/ land cover (LC) data
http://landcover.usgs.gov/landcoverdata.php#asia

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Data Classification
Hydrological
1. Hydrograph of groundwater heads and surface
water level
2. Maps of K, T distributions
3. Maps of storage properties of aquifer
4. Spatial and temporal distribution of rates of
evaporation, recharge, groundwater pumping,
etc

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Data Classification
Physical
1. Geological Map (cross section) which is showing
the vertical system and boundary
2. Topographic map showing surface water bodies
divides (details of drainage, springs, wetlands
and swamps)
3. Land use map
4. Contour maps, showing the elevation of
confining bed
5. Isopach maps, showing the thickness of aquifer
and confining bed

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Boundary Types
Constant/ Specific Head
Specific Flow
C
D
E
F G
I
H
A
B
Constant head (ABC, EFG)
Head Dependent Flow
-Could be recharge (CD)
-No flow (HI)
-Free surface / phrearatic surface (CD)
-seepage surface (DE)

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Basic Types of Boundary Conditions

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Constant Head & Specified
Head Boundaries
Specified Head:
Head (H) is defined as a function of time and space.
Constant Head:
Head (H) is constant at a given location.
• Fully penetrating surface
•water level

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
No Flow and Specified Flow
Boundaries
Specified Flow:
Discharge (Q) varies with space and time.
No Flow:
Discharge (Q) equals 0 across boundary.
Hydraulic conductivity contrasts between
units
– Alluvium on top of tight bedrock. Assume groundwater
does not move across this boundary
- We can use ground-water divide or flow line
•Precipitation/rainfall
•Recharge/discharge area
•Wells

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Head Dependent Flow
Free Surface:
h = Z, or H = f(Z)
e.g. the water table h = z or a
salt water interface
Seepage Surface:
The saturated zone intersects the ground
surface at atmospheric pressure and water
discharges as evaporation or as a downhill
film of flow. The location of the surface is
fixed, but its length varies
•Rivers
•Spring
•Adjacent aquifer

Step 1
Define background
Define purpose(s)
Determine the types
of model
Boundary Conditions
Collecting Data
Flow Model
or
Transport Model
Calculate both head
and flow
Calculate
concentration
h(x,y,t)
c(x,y,t)
output
output

Step 1
Flow Model
Transport Model
Fluid continuity
storage Source/sink
h = hydraulic head
Kx, Ky, Kz = hydraulic conductivity in x,y,z directions
C = substance concentration
t = time
X = distance
U = advection velocity (in x-direction)
D = mixing and dispersion coefficient
S = source and sink due to settling
R = reactivity of chemical / biological process
Q = external loading to the aquatic system from
point/non-point source

Step 1
Flow Model Transport Model
Geometry
Aquifer Parameter
Inflow/Outflow
-Shape of model area
-Thickness and elevation of aquifer
K, T, storage coefficient
-well recharge/discharge
-groundwater recharge
-boundary flow
Prescribed Head
Obserbved discharge
Initial Hydraulic
Parameters
Boundary conditions
Effective porosity
Dispertivities
Input and
abstraction of
pollutants
Decay constant
Adsorbtion
parameters
Initial distribution
of contaminants
Boundary conditions
Source/sink for
contaminants
Contaminants loading
function

Step 1
Flow Model Transport Model
1. Hydraulic head value (in space, time)
2. Groundwater fluxes (over space time)
1. Contaminants concentrations
(in space, time)
2. Contaminant breakthrough
curves at specific locations

Step 2
Determine the types
of model
Choose code
Result
Verification and
calibration
Groundwater modelling software example
MODFLOW - MODULAR THREE-DIMENSIONAL
FINITE-DIFFERENCE GROUND WATER MODEL, by US
Geological Survey (USGS)

Step 2
Determine the types
of model
Choose code
Result
Verification and
calibration
Groundwater modelling software example
Sutra - Model for Ground-Water Flow with Solute or
Energy Transport by USGS

Step 2
Determine the types
of model
Choose code
Result
Verification and
calibration
The calibration process is undertaken until
model simulations match the field observations
to a reasonable degree. The subsequent
sensitivity analysis should be used to test the
overall responsiveness and sensitivity of the
numerical model to certain input parameters.
match with field data
Not match
Collect field data
Is the result of the
model is match
with field data ?

Conclusion
The model should be used to simulate impacts of human
activities on groundwater flow systems, to formulate
sustainable groundwater resources development
scenarios, and to communicate the results to public
and decision-makers.

Groundwater modelling (an Introduction)

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