Transcript Subsurface Hydrology - KNTU homepage webFTP client

Subsurface Hydrology
Unsaturated Zone Hydrology
Groundwater Hydrology
(Hydrogeology)
R = P - ET - RO
ET
ET
P
E
RO
R
R/P=?
Water Table
Groundwater
Processes we might want to model
• Groundwater flow
calculate both heads and flow
v=KI/n
• Solute transport – requires
information on flow (velocities)
calculate concentrations
Types of Models
• Physical (e.g., sand tank)
• Analog (electric analog, Hele-Shaw)
• Mathematical
Hele-Shaw Model
Types of Models
• Physical (e.g., sand tank)
• Analog (electric analog, Hele-Shaw)
• Mathematical
Components of a Mathematical Model
• Governing Equation (Darcy’s law +
water balance eqn) with head (h) as the
dependent variable
• Boundary Conditions
• Initial conditions (for transient problems)
Toth Problem
Groundwater
divide
Laplace Equation
Impermeable Rock
2D, steady state
Groundwater
divide
Conceptual Model
A descriptive representation
of a groundwater system that
incorporates an interpretation of
the geological & hydrological
conditions. Generally includes
information about the water
budget.
Types of Solutions of Mathematical
Models
• Analytical Solutions: h= f(x,y,z,t)
(example: Theis eqn.)
• Numerical Solutions
Finite difference methods
Finite element methods
• Analytic Element Methods (AEM)
Topo-Drive
Finite element model of a version of the
Toth Problem for regional flow in cross
section.
Finite difference models
may be solved using:
• a computer programs (e.g., a
FORTRAN program)
• a spreadsheet (e.g., EXCEL)
MODFLOW
 USGS code
 Finite Difference Model
• MODFLOW 88
• MODFLOW 96
• MODFLOW 2000
Steps in Groundwater Modeling
1. Model Design
2. Calibration (History matching)
3. Prediction (head)