The determination of border width is an important
element of the physical design of irrigation borders. However, the study presented here is based on a one-dimensional
flow analysis; hence, border width is selected as a function
of available flow rate at the field supply channel, field width,
width of available machinery, topography, top soil depth, and
preferred aspect ratio. To the extent that width is determined
on the basis of considerations that are not explicitly related
to performance, it is not considered as a design variable here.
For practical design and management purposes, the solution
of equation 4 can be reduced to the solution of a series of
one-dimensional problems (Zerihun et al., 2001), simplifying the problem significantly. In subsequent sections, the
Ea(L) and Ea(qo) functions are analyzed separately to
establish the existence/absence of convexity and unimodality. Based on the results of the analyses, simple equations that
can be used to calculate approximate optimal length and unit
inlet flow rate are developed