Abstract:
The main objective of the present study was to develop decision
support algorithm to design and select the most feasible sizes of pipes of
irrigation network, it is written in Visual Basic 6.0, runs in a Windows
environment, and uses a database with information on emitters and pipes
available in the market, as well as on crops, soils and the systems under
design. The design procedure is composed of mathematical design module
and a linear optimization module. The mathematical design is based on
hydraulics of flow in pipes, soil characters and crop water demand. The
linear optimization module is presented to improve the technical design by
optimizing size of network pipes using economic criteria. The module
consists of an objective function that maximizes profit at the farm level,
subject to appropriate geometric and hydraulic constraints.
The main items considered affecting cost were: operating pressure within the
network, the pipe diameter, and the pumping cost. User friendly windows
are adopted for handling the databases and to manage the sub-models. The
model allows creating and comparing a set of design alternatives relative to
the pipe system and the emitters, consequently the model is applied,
validated and verified by running it for three hypothetical textbook test cases
and by comparing its results with data obtained from an existing farm
located in Khartoum-North-Sudan. The performance of the drip system in
the existing farm is evaluated by determining water distribution uniformity
and variations of discharge in the network. The results indicate good
distribution uniformity but high variation in discharge along the network.
Hence the model was applied to optimize design and operating parameters of
the farm irrigation system. In all of the tested cases application of the model
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resulted in significant reduction in costs of the sizes of the pipes.
Sensitivity analysis is made for the mathematical design module to
determine hydraulic and operational limitations imposed on the system due
to variations on pump total dynamic head, discharge at network nodes, time
of irrigation, number of emitters and water requirement.
