<s>
ZOOMQ3D	B-Application
is	O
a	O
numerical	O
finite-difference	B-Algorithm
model	O
,	O
which	O
simulates	O
groundwater	O
flow	O
in	O
aquifers	O
.	O
</s>
<s>
The	O
code	O
is	O
written	O
in	O
C++	B-Language
,	O
an	O
object-oriented	B-Language
programming	I-Language
language	I-Language
and	O
can	O
compile	O
and	O
run	O
on	O
Windows	B-Application
and	O
Unix	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
ZOOMQ3D	B-Application
applies	O
a	O
quasi-three-dimensional	O
finite-difference	B-Algorithm
approximation	O
to	O
the	O
general	O
three-dimensional	O
governing	O
partial	O
differential	O
groundwater	O
flow	O
equation	O
:	O
</s>
<s>
is	O
a	O
volumetric	O
flux	B-General_Concept
per	O
unit	O
volume	O
representing	O
sources	O
and/or	O
sinks	O
of	O
water	O
,	O
where	O
negative	O
values	O
are	O
abstractions	O
,	O
and	O
positive	O
values	O
are	O
injections	O
(	O
T−1	O
)	O
and	O
,	O
</s>
<s>
ZOOMQ3D	B-Application
takes	O
a	O
simplifying	O
approach	O
to	O
the	O
solution	O
of	O
the	O
three-dimensional	O
equation	O
by	O
recognising	O
that	O
in	O
many	O
aquifers	O
it	O
is	O
possible	O
to	O
identify	O
a	O
layered	O
structure	O
.	O
</s>
<s>
Feature	O
Description	O
Multiple	O
layers	O
ZOOMQ3D	B-Application
can	O
incorporate	O
multiple	O
layers	O
of	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
.	O
</s>
<s>
This	O
because	O
the	O
flow	O
through	O
low	O
permeability	O
layers	O
,	O
which	O
is	O
assumed	O
to	O
be	O
vertical	O
,	O
is	O
represented	O
by	O
the	O
vertical	O
leakage	O
term	O
connecting	O
two	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
within	O
the	O
upper	O
and	O
lower	O
aquifer	O
.	O
</s>
<s>
Local	O
grid	O
refinement	O
ZOOMQ3D	B-Application
incorporates	O
a	O
mesh	O
refinement	O
procedure	O
which	O
aids	O
the	O
solution	O
of	O
problems	O
related	O
to	O
scale	O
.	O
</s>
<s>
The	O
density	O
of	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
can	O
be	O
increased	O
by	O
adding	O
successively	O
finer	O
rectangular	O
grids	O
in	O
discrete	O
areas	O
of	O
the	O
model	O
domain	O
.	O
</s>
<s>
At	O
confined	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
transmissivity	O
and	O
storage	O
are	O
independent	O
of	O
groundwater	O
head	O
.	O
</s>
<s>
Finite	B-Algorithm
difference	I-Algorithm
nodes	O
dewater	O
as	O
the	O
groundwater	O
head	O
drops	O
below	O
their	O
base	O
.	O
</s>
<s>
In	O
this	O
case	O
the	O
node	O
is	O
removed	O
from	O
the	O
matrix	O
of	O
finite	B-Algorithm
difference	I-Algorithm
equations	I-Algorithm
.	O
</s>
<s>
Different	O
hydraulic	O
parameter	O
values	O
can	O
be	O
specified	O
at	O
each	O
finite	B-Algorithm
difference	I-Algorithm
node	O
and	O
hydraulic	O
conductivity	O
may	O
be	O
different	O
in	O
the	O
x	O
and	O
y-directions	O
.	O
</s>
<s>
The	O
re-wetting	O
of	O
model	O
nodes	O
depends	O
on	O
the	O
groundwater	O
head	O
in	O
adjacent	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
.	O
</s>
<s>
Head-dependent	O
leakage	O
nodes	O
In	O
addition	O
to	O
rivers	O
,	O
a	O
second	O
head-dependent	O
leakage	O
mechanism	O
is	O
included	O
in	O
ZOOMQ3D	B-Application
.	O
</s>
<s>
The	O
flow	O
through	O
leakage	O
nodes	O
is	O
proportional	O
to	O
the	O
difference	O
between	O
its	O
elevation	O
and	O
the	O
groundwater	O
head	O
at	O
the	O
finite	B-Algorithm
difference	I-Algorithm
node	O
to	O
which	O
it	O
is	O
connected	O
.	O
</s>
<s>
The	O
flow	O
out	O
of	O
a	O
spring	O
depends	O
on	O
the	O
transmissivity	O
of	O
the	O
surrounding	O
finite	B-Algorithm
difference	I-Algorithm
nodes	O
.	O
</s>
<s>
The	O
groundwater	O
flow	O
model	O
ZOOMQ3D	B-Application
is	O
one	O
of	O
the	O
codes	O
in	O
the	O
ZOOM	O
family	O
of	O
numerical	O
groundwater	O
models	O
which	O
also	O
consists	O
of	O
the	O
advective	O
transport	O
particle	O
tracking	O
code	O
ZOOPT	O
and	O
the	O
distributed	O
recharge	O
model	O
ZOODRM	O
.	O
</s>
<s>
Each	O
of	O
these	O
models	O
has	O
been	O
developed	O
using	O
object-oriented	B-Language
techniques	O
,	O
a	O
programming	B-General_Concept
approach	O
commonly	O
applied	O
in	O
commercial	O
software	O
development	O
but	O
only	O
relatively	O
recently	O
adopted	O
in	O
numerical	O
modelling	O
for	O
scientific	O
analysis	O
.	O
</s>
<s>
ZOOMQ3D	B-Application
and	O
ZOOPT	O
have	O
been	O
developed	O
through	O
a	O
tri-partite	O
collaboration	O
between	O
the	O
School	O
of	O
Civil	O
Engineering	O
of	O
the	O
University	O
of	O
Birmingham	O
,	O
UK	O
,	O
the	O
British	O
Geological	O
Survey	O
and	O
the	O
Environment	O
Agency	O
of	O
England	O
and	O
Wales	O
.	O
</s>
<s>
A	O
link	O
exists	O
between	O
ZOOMQ3D	B-Application
and	O
the	O
geological	O
modelling	O
software	O
GSI3D	B-Application
.	O
</s>
<s>
The	O
link	O
facilitates	O
the	O
transfer	O
of	O
the	O
structure	O
of	O
a	O
geological	O
model	O
into	O
a	O
ZOOMQ3D	B-Application
groundwater	O
model	O
.	O
</s>
<s>
After	O
a	O
GSI3D	B-Application
geological	O
model	O
is	O
constructed	O
it	O
can	O
be	O
used	O
to	O
create	O
a	O
hydrogeological	O
model	O
of	O
an	O
aquifer	O
.	O
</s>
<s>
Once	O
this	O
has	O
been	O
completed	O
the	O
resulting	O
hydrogeological	O
model	O
can	O
then	O
be	O
converted	O
to	O
a	O
layered	O
ZOOMQ3D	B-Application
groundwater	O
model	O
.	O
</s>
