39
At K
1+1/2
C =
i
- (-
2 k
AZ C
i
-)
(22)
B = 1 A C
i i i
k k
At K K
k i-1/2 i+1/2
D = h + (
i i k
AZ C
(23)
At
) S
k i
C
i
(24)
Boundary Conditions. The boundary condition for the surface grid
was variable. A flux boundary condition was used to simulate
infiltration during irrigation, and a no flux boundary condition was
used for redistribution. Evaporation from the soil surface was included
in the water extraction term. Equation (20) was modified for the
surface boundary condition such that
k+1
k+1
B h
1 1
+ C h
1 2
1
where
and
B = 1
(25)
(26)
At
k
D = h + (
1 1
Az
Qs
1+1/2
At
- s
k 1
*1
(27)