Page 225 - Biosystems Engineering

Design of Sustainable W ater Management Systems 203

the type of crop and potential return on investment. The following
sections briefly describe these methods.
Surface Irrigation Systems
In its most primitive form, wild flooding has been practiced with
only 50 percent of the applied water beneficially stored within the
plant root zone. In sloping terrain, basin irrigation has been used to
allow more time for infiltration into the soil. The graded border sys-
tem is used in hilly terrain, where the water is allowed to advance
over the sloping land while it continues to infiltrate vertically into the
root zone. Such systems require a very good understanding of the
soil’s infiltration characteristics. Biosystems engineers have modeled
such systems to develop a design that will maintain uniform infiltra-
tion depth along the length of the field. Furrow irrigation systems
allow water to flow along the length of the field, whereas plants
growing on the ridges between the furrows will take up the water
uniformly. The uniformity of depth of infiltration along the length of
the furrow is of major concern. Biosystems engineers have improved
on the design of these systems and developed an automated method
called cablegation system (Kemper et al. 1981). Figure 6.2 shows a
cablegation system designed and set up by the author for irrigating
corn in Coimbatore, India. The cablegation system applies water
sequentially to a few furrows at a time. The system applies water at

Pipe

Wheel

Stilling tank

FIGURE 6.2 A cablegation system irrigating corn in Coimbatore, southern
India.