Geology Reference
In-Depth Information
/0
/0
H
hx
H
hx
, x
@H 2
Neumann
K
H
n
H
n
where H h ( x )/H n is the specified outward normal gradient to the boundary
segment
H 2 .
Stream or River Head Dependent Boundary
The rate of flow into or out of the aquifer is a function of the aquifer head,
elevation of stream bed, and the leakage between the aquifer and the stream
or river. This condition is used to model streams or small rivers in poor
connection with the aquifer, upward leakage in artesian aquifers, drains and
overlying aquitards. This is also known as third type boundary condition,
mixed or Induced flux or mathematically Cauchi Condition/Robbins
Condition.
@H 3 Cauchi/Robbins
where C 0 is specified function value along the boundary segment H and
and are specified functions.
h ( x ) +
' H
h ( x )/
H
n = C 0 , x
GROUNDWATER MODELLING
Models are the tools or device that represents an approximation of a field
situation or real system or natural phenomena. These models are applied to
a variety of environmental problems especially for understanding and the
interpretation of the issues having complex interaction of many variables in
the system.
Groundwater flow models are used to calculate the rate and direction of
movement of groundwater through aquifers and confining units in the
subsurface. These calculations are referred to as simulations. The simulation
of groundwater flow requires a thorough understanding of the hydrogeologic
characteristics of the site. The hydrogeologic investigation should include a
complete characterization of the following:
Subsurface extent and thickness of aquifers and confining units
(hydrogeologic framework),
Hydrologic boundaries (also referred to as boundary conditions), which
control the rate and direction of movement of groundwater,
Hydraulic properties of the aquifers and confining units,
A description of the horizontal and vertical distribution of hydraulic head
throughout the modelled area for both beginning (initial conditions),
equilibrium (steady-state conditions) and transitional conditions when
hydraulic head may vary with time (transient conditions), and
Distribution and magnitude of groundwater recharge, pumping or injection
of groundwater, leakage to or from surface-water bodies, etc. (sources or
sinks, also referred to as stresses). These stresses may be constant
(unvarying with time) or may change with time (transient).
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