Environmental Engineering Reference
In-Depth Information
CHAPTER 7
The Sediment Transport Model
and its Applications
7.1 INTRODUCTION
The amount of water and sediment that enters into an irrigation canal
will vary during the growing season and, moreover, throughout the entire
life of an irrigation system. Variations in crop water requirement, water
supply, size of the irrigated area, planned cropping pattern and sediment
concentration frequently occur during the lifetime of irrigation systems.
The design of canals and control structures incorporates a certain degree
of flexibility in the delivery of different irrigation flows at fixed or variable
supply levels. This design approach also assumes that the conveyance of
the incoming sediment is, for the given design conditions, in a state of
equilibrium. Once the flow conditions diverge from the design values, the
flow velocity and thus the capacity to transport the sediment load will vary
in time and space along the irrigation network. In these circumstances the
initial assumptions related to the conveyance of the sediment load in or
below equilibrium conditions are no longer valid for these changed flow
conditions. Due to these changes, the sediment transport in irrigation
canals will essentially be under non-equilibrium conditions. Therefore,
the transport will strongly depend on the variation of the initial design flow
and the changes in the incoming sediment load during the irrigation season
and the lifetime of the canal. For this reason sediment transport should be
viewed in a more general context, which should take into account the time
and place of the varying operation requirements of the irrigation system.
The sediment transport model SETRIC offers the possibility to predict
the sediment deposition and erosion in time and space, and for particular
flow conditions and incoming sediment loads. This chapter will present
some examples of sediment transport modelling in irrigation canals with
the aim of showing the possible applications of this original model and of
improving the understanding of sediment transport processes for situations
commonly encountered in irrigation systems.
Sediment that enters a canal network can either be transported with-
out any deposition along the canal or the sediment concentration can
adapt itself from a non-equilibrium condition to the equilibrium sediment
 
 
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