1. Prof. S. N. Panda Head, School of Water Resources
Groundwater Modelling of Ganga Basin – Opportunities and Challenges
Prof. S. N. Panda Head, School of Water Resources

2. Physiography and groundwater flow of Ganga basin
(Source: Ministry of Environment and Forests, Government of India)

3. Annual groundwater draft in comparison with net annual availability in Ganga basin
(Source: Ministry of Environment and Forests, Government of India)

4. Annual replenishable groundwater in comparison with annual draft in Ganga basin
(Source: Ministry of Environment and Forests, Government of India)

5. Schematic illustration for evaluating stream-aquifer interaction
Inflow or leakage to/from groundwater
Change in storage
Reach inflow
Reach Outflow
Stream Reach
Evaporation
Groundwater inflow
Groundwater outflow
Stream inflow
Stream outflow
Recharge to groundwater
Evapotranspiration
Rainfall

6. Problems with groundwater in the Ganga Basin
Imbalance in groundwater draft
Waterlogging and salinity in canal commands
Groundwater pollution

7. Types of Terrestrial Water
Surface Water
Soil Moisture
Ground water

8. Movement of water through the hydrologic cycle
(Source: usgs.gov)

9. Effluent and influent streams
Gaining stream
Losing stream with shallow watertable
Base flow
Losing stream with deep watertable

10. Water Balance Concept The basic concept of groundwater balance is:
Input to the system ‑ outflow from the system = change in storage of the system (over a period of time)

11. Flow components for assessing groundwater balance
Boundary Pr ET
Per
Cap
Qdr
Qper
Qlsi
Qdo
Qup
Qlso
Clay
Watertable
Sgrw
Overland Flow Ir
Seepage
Pumping well

12. Groundwater Balance Equation
Considering the various inflow and outflow components in a given study area, the groundwater balance equation can be written as:
Rr + Rc + Ri + Rt + Si + Ig = Et + Tp + Se + Og + S
where,
Rr = recharge from rainfall
Rc = recharge from canal seepage
Ri = recharge from field irrigation
Rt = recharge from tanks
Si = influent seepage from rivers
Ig = inflow from other basins
Et = evapotranspiration from groundwater
Tp = draft from groundwater
Se = effluent seepage to rivers
Og = outflow to other basins; and
S = change in groundwater storage

13. Groundwater Survey and Investigation
Water table contour map
Water table contour map showing a local mound and depression in water table and direction of groundwater flow

14. Flow net
Flow net technique for estimation of subsurface horizontal flow

15. Depth-to-Water Table Map or Isobath Map

16. Groundwater Quality Map

17. Components of a Mathematical Model Governing Equation
(Darcy’s law + water balance equation) with head (h) as the dependent variable
Boundary Conditions
Initial conditions (for transient problems)

18. General governing equation
for steady-state, heterogeneous, anisotropic conditions, without a source/sink term
with a source/sink term

19. D is dispersion coefficient v is velocity
Allows for multiple
chemical species
Dispersion
Chemical
Reactions
Advection
Source/sink term
Change in concentration
with time
is porosity
D is dispersion coefficient
v is velocity

20. Model Grids
Finite Difference Grid
Finite Element Grid

21. Modelling Process Conceptual Model Update Model Calibrate Model
Compare Model and Field
Mathematical Model
Computation
Conclude study
(Decisions & Recommendations)
Satisfactory Results
Poor Fit
Unsatisfactory Results

22. Opportunities and Challenges in the Ganga Basin
Wide variation in climate from semi-arid to sub-humid/sub-tropical regions
Large-scale spatial variation in
Soil texture and land-use
Type of aquifers and its properties
Spatio-temporal variation in
- meteorological parameters associated with uncertainties
- groundwater recharge and discharge components
Groundwater level monitoring is not being done regularly and intensively
Setting up/optimising monitoring networks and setting up groundwater protection zones
Groundwater resources too need to be planned and managed for maximum basin-level efficiency.

23. THANK YOU

25. Diversified geological climatological and topographic set-up, giving rise to divergent ground water situations
Excessive use of our rivers, are causing downstream problems, of water quality and ecological stress.
Climate change impacts directly on the availability of water resources both in space and time.
The precarious balance between growing demands and supplies brings forth the importance of maintaining quality of both surface and ground water.

26. Application of existing groundwater models include water balance (in terms of water quantity)
gaining knowledge about the quantitative aspects of the unsaturated zone
simulating of water flow and chemical migration in the saturated zone including river-groundwater relations
assessing the impact of changes of the groundwater regime on the environment

27. State-wise distribution of the drainage area of Ganga river
(Source: Status paper on river Ganga, NRCD, MoEF, 2009)

28. Soil types in Ganga basin
(Source: Central Pollution Control Board, National River Conservation Directorate (MoEF) (2009))

29. Data requirement for groundwater balance study over a given time period:
Precipitation
River
Canal
Tank
Water table
Groundwater draft
Aquifer parameters
Land use and cropping patterns

30. Management of a groundwater system, means making such decisions as:
The total volume that may be withdrawn annually from the aquifer.
The location of pumping and artificial recharge wells, and their rates.
Decisions related to groundwater quality.
Groundwater contamination by:
Hazardous industrial wastes
Leachate from landfills
Agricultural activities such as the use of fertilizers and pesticides

31. Groundwater Modelling
The only effective way to test effects of groundwater management strategies
Conceptual model Steady state model Transient model
Processes
Groundwater flow (calculate both heads and flow)
Solute transport – requires information on flow (calculate concentrations)

32. Model Design Conceptual Model Selection of Computer Code
Model Geometry
Grid
Boundary array
Model Parameters
Boundary Conditions
Initial Conditions
Stresses

33. Modelling Process Conceptual Model Update Model Calibrate Model
Compare Model and Field
Mathematical Model
Computation
Conclude study
(Decisions & Recommendations)
Satisfactory Results
Poor Fit
Unsatisfactory Results

34. General governing equation for transient, heterogeneous, and anisotropic conditions
Kx, Ky, Kz are components
of the hydraulic conductivity
Specific Storage
Ss = V / (x y z h)

35. Types of Solutions of Mathematical Models
Analytical Solutions: h= f(x, y, z, t)
Numerical Solutions
Finite difference methods
Finite element methods

36. Model Design Conceptual Model Selection of Computer Code
Model Geometry
Grid
Boundary array
Model Parameters
Boundary Conditions
Initial Conditions
Stresses

37. Managed Aquifer Recharge

38. Suitability of groundwater in increasing dry season productivity in the coastal region of the Ganga basin
How the recharge mechanisms can be used to reduce salinity.
Climate change impact on groundwater.

40. Methods for groundwater recharge

41. Mismatch between water supply and demand
Management of Excess Rainwater
Mismatch between water supply and demand
Possible solutions
Rainwater conservation and recycling
Multiple use of harvested water
Managed aquifer recharge
Management of stagnant water in lowland areas

42. Rainwater Conservation
a. Storage of rainwater on surface reservoir
b. Recharge to ground water
Pits
Trenches
Dug wells
Hand pumps
Recharge wells
Recharge shafts
Lateral shafts with bore wells
Spreading techniques

43. Methods of Rainwater Storage
Infiltration
Injection
Increased font size

45. Benefits Ideal solution to water problems in water stress areas
Capture and storage of water in monsoon when rainwater is abundant
More water will be available for summer use
Rise in groundwater level - Improves declining aquifers
May increase base flow to streams
Mitigates the effects of drought
Reduces the runoff which chokes the storm water drains
Flooding of roads and low land areas are reduced
Quality of water improves
Soil erosion will be reduced
Saving of energy per well for lifting of ground water – 1 m rise in water level saves about 0.40 KWH of electricity

46. What is Managed Aquifer Recharge (MAR)?
Managed Aquifer Recharge is:
The infiltration or injection of water into an aquifer
Water can be withdrawn at a later date but also left in the aquifer (e.g. to benefit the environment)
Why Consider MAR?
Allows storage of water in wet seasons
Improvement in groundwater quality
Allows increased use of groundwater from other parts of the aquifer systems
To stop seawater intrusion in coastal areas
To maintain or increase available water supplies for use in agriculture, drinking water supply, and industry

51. The point of origin of the Ganga, known as the Gangotri (left) and Devprayag, the point of confluence of the Alaknanda (from right) and Bhagirathi (from left) to form the Ganga (right).

53. Ganga River Basin, India
The river systems in India are grouped into four broad categories:
The Himalayan rivers
The Peninsular rivers
The Coastal rivers
The Inland rivers
The Ganga River (length: 2525 km long; catchment area: km2) is fed by runoff from
Vast land area bounded Himalaya in the north.
Peninsular highlands and the Vindhya Range in the south.
The states of Haryana, Rajasthan, Uttar Pradesh and West Bengal, comprising 50% of the basin area.
The basin spreads over four countries: India, Nepal, Bangladesh and China.

54. Soil and rainfall (isohyetal) map of Ganga Basin (Source: Ministry of Environment and Forests, Government of India)

55. Vegetation Types of Ganga Basin (Source: Ministry of Environment and Forests, Government of India)

56. Groundwater
An important component of water resource systems and source of clean water.
More abundant than Surface Water
Extracted from aquifers through pumping wells and supplied for domestic use, industry and agriculture.
With increased withdrawal of groundwater, the quality of groundwater has been continuously deteriorating.
Linked to Surface Water systems and sustains flows in streams

57. Groundwater in Hydrologic Cycle
(Source: physicalgeography.net)

58. Dynamic Groundwater Resources of India
Total replenishable groundwater in the country = 433 BCM
5,723 units (blocks, talukas, mandals, districts) assessed –
15% over-exploited
4% critical
10% semi-critical
Delhi, Haryana, Punjab, Rajasthan are overusing their groundwater resources.
Andhra Pradesh has the highest number of over-exploited units.
The agricultural (tube-well dependent) state of Punjab has developed (usage compared to availability) its groundwater upto 145%.
Delhi is mining 170% of its groundwater.
Countrywide percentage of groundwater development is 58%.

59. Annual replenishable groundwater in comparison with annual draft in Ganga basin

60. Ground Water and Surface Water Interaction
Ground water and surface water contained in the hydrological system are closely interrelated
The studies examines the processes of ground water flow generation and estimation of ground water discharge including ground water discharge to rivers (base flow)
In a ground water basin, it is common to identify several aquifers separated either by less permeable or impermeable layers

61. the upper aquifer is recharged through the bed and banks of the river
the upper aquifer is recharged through the bed and banks of the river. The lower aquifer is recharged through the intervening aquitard
finite difference equations describes the response of the aquifer system to applied stresses
quasi three-dimensional model simulates a ground water system having any number of aquifers

62. The studies on the ground water/surface water interrelationship made it possible to solve a number of important scientific and practical problems :
to estimate base flow and, therefore, sustained low river discharges of different probabilities
to estimate the ground water contribution to total water resources and the water balance of regions
to evaluate quantitatively the natural ground water resources for determining the prospects of their use within large areas and as a component of the safe ground water yield

63. The methods for estimating the ground water discharge of the upper hydrodynamic zone are fairly well developed as compared to deep artesian aquifers and their contribution to surface runoff

64. Seawater Intrusion
A natural process that occurs in virtually all coastal aquifers.
Defined as movement of seawater inland into fresh groundwater aquifers, as a result of
higher seawater density than freshwater
groundwater withdrawal in coastal areas

65. Sea Water Intrusion
In the coastal margins of ground water basin, the lowering of water level or potentiometric head results in the intrusion of sea water
Inland gradient for saline intrusion result from pumping at rate higher than the recharge to the ground water basin
wedge-shaped intrusion occurs as sea water is approximately times heavier than fresh water

66. Field surveys (geophysical and geochemical studies) can only reveal the present state of seawater intrusion but can not make impact assessment and prediction into the future
Mathematical models are needed for these purposes
Ghyben-Herzberg relation is a highly simplified model
Dynamic movement of groundwater flow and solute transport needs to be considered
A density-dependent solute transport model including advection and dispersion is needed for the modelling

67. Flow Equation
Advection-Dispersion Equation
Distribution of Head
Velocity Field
Solute Transport Model
Concentration distribution in time and space

68. Ground Water Pollution
Restoration to the original, non-polluted state of polluted ground water is more difficult than surface water
Geologic and hydrogeologic setting along with magnitude of the pollution hazard for a specific incident must be evaluated.
Movement of contaminants and its control largely depends on the hydrogeologic environment
Processes of migration and alterations present in ground water are also present in the unsaturated zone

69. Remedial action can be classified into three broad categories
Physical containment measures, including slurry trench cutoff walls, grout curtains, sheet piling, and hydrodynamic control
Aquifer rehabilitation, including withdrawal, treatment, reinjection (or recharge), and in-situ treatment such as chemical neutralization and biological neutralization
Withdrawal, treatment and use

70. use of models provide more appropriate and rigorous method for integrating all the available data together
It evaluates the response of the aquifer system to a contamination event
The models are derived from the expression of the flow and transport processes in terms of mathematical equations
Equations are solved by incorporating appropriate parameter values and boundary conditions

71. Seawater Intrusion
Before extensive pumping
After extensive pumping by many wells
Pumping causes a cone of depression and draws the salt water upwards into the well.

72. Groundwater An important component of water resource systems.
Extracted from aquifers through pumping wells and supplied for domestic use, industry and agriculture.
With increased withdrawal of groundwater, the quality of groundwater has been continuously deteriorating.
Water can be injected into aquifers for storage and/or quality control purposes.

73. MANAGEMENT means making decisions to achieve goals without violating specified constraints.
Once contamination has been detected in the saturated or unsaturated zones, requires the prediction of the path and the fate of the contaminants, in response to the planned activities.
Any monitoring or observation network must be based on the anticipated behavior of the system.
The tool for understanding the system and its behavior and for predicting the response is the model.
Usually, the model takes the form of a set of mathematical equations, involving one or more partial differential equations. We refer to such model as a mathematical model.
The preferred method of solution is the analytical solution.

74. For most practical problems we transform the mathematical model into a numerical one, solving it by means of computer programs.

75. What is a “model”?
Any “device” that represents approximation to field system
Physical Models
Mathematical Models (Analytical and Numerical)
Modeling begins with formulation of a concept of a hydrologic system and continues with application of, for example, Darcy's Law to the problem, and may culminate in a complex numerical simulation.

76. TYPES OF MODELS CONCEPTUAL MODEL MATHEMATICAL MODEL ANALOG MODEL
PHYSICAL MODEL

77. Line diagram of the Ganga with major tributaries
(Source: Status paper on river Ganga, NRCD, MoEF, 2009)

78. Importance of ground water flow models
Construct representations and helps understanding the interrelationships between elements of hydrogeological systems
Efficiently develop a sound mathematical representation
Make reasonable assumptions and simplifications
Understand the limitations of the mathematical representation and interpretation of the results
I want to show you how to use the power of hydrogeological modeling
You should be able to do more than just go through the motions of hydrogeological modeling, you should to be able to use the modeling process to further your understanding of the hydrogeological system that you are investigating.
This will hinge on the development of a sound conceptual model, a concept in your mind of how the plumbing works and how it relates to the problem to be addressed
We will use mathematical models (analytical and numerical) as tools to address these problems
The next step is to learn how to convert your conceptual model into a mathematical model. This could be as simple as applying 1-D Darcy’s Law and as complex as setting up and calibrating a 3-D, transient numerical model.
In any case the procedure is the same: 1) Define the problem in lay-terms (demonstrate the significance to your audience), 2) define the specific objectives in technical (hydrogeological) terms, 3) Develop a conceptual model [site description and general hydrogeology], 4) convert the conceptual model into mathematical models that will address the objectives [methodology] 5) determine specifically where you will get the information from to set up your model [more methodology], 6) set up your model, calibrate and use it to address the objective [results]
This will also help write the documentation which you should be writing all along

79. Groundwater models can be used :
To predict or forecast expected artificial or natural changes in the system.
To describe the system in order to analyse various assumptions
To generate a hypothetical system that will be used to study principles of groundwater flow associated with various general or specific problems.

80. Processes to model Transport
Groundwater flow
Transport
Particle tracking: requires velocities and a particle tracking code calculate path lines
(b) Full solute transport: requires velocites and a solute transport model calculate concentrations

81. Processes we need to model
Groundwater flow
calculate both heads and flows (q)
Solute transport – requires information on flow (velocities)
calculate concentrations
v = q/n = K I / n
Requires a flow model and a solute transport model.

82. Modelling Process Establish the Purpose of the Model
Develop Conceptual Model of the System
Select Governing Equations and Computer Code
Model Design
Calibration
Calibration Sensitivity Analysis
Model Verification
Prediction
Predictive Sensitivity Analysis
Presentation of Modeling Design and Results
Post Audit
Model Redesign

83. Mathematical model:
Simulates ground-water flow and/or solute fate and transport indirectly by means of a set of governing equations thought to represent the physical processes that occur in the system.
(Anderson and Woessner, 1992)

84. Storage coefficient (S) is either storativity or specific yield.
General 3D equation
2D confined:
2D unconfined:
Storage coefficient (S) is either storativity or specific yield.
S = Ss b & T = K b

85. Groundwater flow is described by Darcy’s law.
This type of flow is known as advection.
Linear flow paths
assumed in Darcy’s law
True flow paths
The deviation of flow paths from
the linear Darcy paths is known
as dispersion.
Figures from Hornberger et al. (1998)

86. In addition to advection, we need to consider two other processes in transport problems.
Dispersion
Chemical reactions
Advection-dispersion equation
with chemical reaction terms.

87. advection-dispersion equation
groundwater flow equation

88. advection-dispersion equation
groundwater flow equation

89. Flow Equation:
1D, transient flow; homogeneous, isotropic,
confined aquifer; no sink/source term
Transport Equation:
Uniform 1D flow; longitudinal dispersion;
No sink/source term; retardation

90. Flow Equation:
1D, transient flow; homogeneous, isotropic,
confined aquifer; no sink/source term
Transport Equation:
Uniform 1D flow; longitudinal dispersion;
No sink/source term; retardation

91. Selection of Computer Code
Conceptual Model
A descriptive representation of a groundwater system that incorporates an interpretation of the geological & hydrological conditions.
Selection of Computer Code
Depends largely on the type of problem(Flow, solute, heat, density dependent etc. along with 1D, 2D, 3D)
Model geometry
It defines the size and the shape of the model. It consists of model boundaries, both external and internal, and model grid.
Grid
In Finite Difference model, the grid is formed by two sets of parallel lines that are orthogonal. In the centre of each cell is the node

92. Boundaries
Physical boundaries are well defined geologic and hydrologic features that permanently influence the pattern of groundwater flow (faults, geologic units, contact with surface water etc.)
Hydraulic boundaries are derived from the groundwater flow net and therefore “artificial” boundaries set by the model designer. They can be no flow boundaries or boundaries with known hydraulic head.

93. Model Parameters Initial Conditions
Time, Space (layer top and bottom), Hydrogeologic characteristics (hydraulic conductivity, transmissivity, storage parameters and effective porosity)
Initial Conditions
Values of the hydraulic head for each active and constant-head cell in the model.

94. Calibration and Validation
Calibration parameters are uncertain parameters whose values are adjusted during model calibration.
Typical calibration parameters include hydraulic conductivity and recharge rate.
Model validation is to determine how well the mathematical representation of the processes describes the actual system behavior.

95. Groundwater Flow Models MODFLOW
(Three-Dimensional Finite-Difference Ground-Water Flow Model)
When properly applied, MODFLOW is the recognized standard model.
Ground-water flow within the aquifer is simulated in MODFLOW using a block-centered finite-difference approach.
Layers can be simulated as confined, unconfined, or a combination of both.
Flows from external stresses such as flow to wells, areal recharge, evapotranspiration, flow to drains, and flow through riverbeds can also be simulated.

96. Other Models MT3D (A Modular 3D Solute Transport Model)
FEFLOW (Finite Element Subsurface Flow System)
HST3D (3-D Heat and Solute Transport Model)
SEAWAT (Three-Dimensional Variable-Density Ground-Water Flow)
SUTRA (2-D Saturated/Unsaturated Transport Model)
SWIM (Soil water infiltration and movement model)
VISUAL HELP(Modeling Environment for Evaluating and Optimizing Landfill Designs)
Visual MODFLOW (Integrated Modeling Environment for MODFLOW and MT3D)

97. Several methods to control saline intrusion
Reduction of ground water extraction
Artificial recharge by spreading
Physical barrier
Mathematical modelling of unsteady flow of saline and fresh water in aquifer