SETRIC, a Mathematical Model for Sediment Transport in Irrigation Canals - Sediment Transport in Irrigation Canals: A New Approach - page 174

The design steps include:
- the gate opening is calculated from the downstream water level (set
point) and the design and tuning parameters;
- then the maximum angle of the gate opening is determined, which gives
the relative vertical gate opening;
- the gate opening is used to find the head-discharge relation of the gate.

The computation procedure for the SETRIC module for downstream
control is as follows:
- the hydraulic computations start downstream of the most downstream
gate for the given discharge and water level;
- the downstream water level results in the difference (the actual decre-
ment) between the elevation of the gate axis and the downstream water
elevation;
- the established actual decrement gives the gate opening angle;
- the gate opening angle gives the actual gate opening;
- this gate opening and the discharge lead to the water level upstream of
the gate;
- the upstream water level is then the boundary for the next upstream
canal reach;
- the water surface profile is computed from the tail structure to the first
upstream cross regulator taking into account factors such as offtake
withdrawal. The gradually varied glow equation is then solved by the
predictor-corrector method;
- the procedure is continued until the upstream end of the first, most
upstream canal reach;
- after the hydraulic calculation follow the sediment transport computa-
tions that will start from the upstream boundary and go in a downstream
direction to the end of the canal;
- then in the next time step the same procedure will be repeated.

The hydraulic and sediment transport computations are performed for
every time step. In one step first the hydraulic computations are performed
and next the sediment transport computations are done according to the
hydraulic conditions at the end of that time step. The flow changes will
affect the sediment transport behaviour and the sediment transport will
influence the canal hydraulics in the next time step.

Sediment aspects
The sediment aspects are fully comparable with the aspects for

upstream-controlled irrigation systems (see Section 6.1.4).

Irrigation aspects
- The model of the irrigation network can be composed of a main canal
and secondary canals with tertiary outlets. Each canal is divided into
several reaches or sections;