Irrigation System Designing - Practices of Irrigation and On-farm Water Management - page 84

water equations. For the first case, the governing equations were solved by using
a split-operator approach. For the second case, the governing equations were solved
by using a split-operator approach using the method of characteristics coupled
with two-dimensional Taylor series expansion for interpolation and calculation of
diffusion terms.
3.3.4 Existing Models for Basin Irrigation Design
3.3.4.1 COBASIM
A two-dimensional simulation model, titled “contour basin simulation model”
(COBASIM) was developed by Khanna et al. ( 2003a , b ) . It simulates the over-
land flow hydraulics and infiltration processes that occur in contour basin layouts.
The model is capable of simulating contour basin layouts of regular and irreg-
ular shape and size. The main objective of developing the simulation tool was
to enable designers and practitioners to simulate the behavior of multiple design
scenarios.
3.3.4.2 BASCAD
It was developed by Boonstra and Jurriens ( 1988 ) for level basin design. BASCAD
simulates advance with a zero-inertia model in real time, then uses a volume balance
to determine a single recession time and the final distribution of infiltrated water.
The program allows the user to start by providing the computer with very limited
data, have the computer provide “ballpark” estimates for unknown parameters, and
proceed with the user providing values for more parameters. The user does not have
direct control over performance measures.
3.3.4.3 SIRMOD, WinSRFR, SADREG
These models have been described in border irrigation section.
3.4 Furrow Irrigation System Design
Furrows are sloping channels formed in the soil. The amount of water that can be
applied in a single application via furrow (or in other conventional surface irrigation,
that is, flood or border irrigation or, to some extent, sprinkler irrigation) depends
upon the ability of the soil to absorb water. The irrigation process in a furrow is iden-
tical to the irrigation process in a border, with the only difference that the geometry
of the cross-section, and as such the infiltration process, is different. Among surface
irrigation systems, furrow irrigation with cutback is commonly used because of its
potential higher irrigation efficiency, lower cost and relative simplicity.