In irrigation borders, inflow cutoff can occur in the course
of the advance phase or at the end of the wetting phase.
Advance-phase cutoff offers some practical advantages over
post-advance cutoff. Wattenburger and Clyma (1989a,
1989b) and Clemmens (1998) observed that level basin
designs that use distance-based inflow cutoff criterion
(i.e., advance-phase inflow cutoff) are less sensitive to wide
variations in decision variables and system parameters.
Clemmens (1998) stated that design decisions based on
distance-based cutoff criterion are more transferable to
irrigators and allow basin designs to be adapted to local
practices. Experience with simulation experiments shows
that similar observations can be made with regard to the
sensitivity of the Ea(qo) function of border irrigation systems
when inflow cutoff occurs during the advance phase
(e.g., fig. 4a). Advance-phase cutoff has the effect of dampening the influence that changes in qo can have on the runoff
fraction (Rf) over a large interval of qo (fig. 4a). As a result,
Ea becomes nearly insensitive to changes in qo over a
relatively wide range (a 300% increase in qo resulted only in
a 4.5% change in Ea, fig. 4a)