SETRIC, a Mathematical Model for Sediment Transport in Irrigation Canals - Sediment Transport in Irrigation Canals: A New Approach - page 169

• drops : incorporated as a difference in bottom level at the boundary

between two reaches;

•

AVIO and AVIS gates for downstream control.
- The variation in crop water requirement during the irrigation season can
be incorporated and mainly depends on the climate, cropping pattern,
stage of the crops, leaching requirement and water losses. The growing
season is divided into four stages depending on the crop development
and climate (FAO, 1998). The water supply in the model can be attuned
to the varying water requirement and follows the changes in area and
time;
- The irrigation schedule can include rotational turns of water supply
(intermittent) to the secondary canals or tertiary off takes; when there
is no flow in the canals no sediment deposition will occur in the model
during the turn-off time;
- The composite roughness for a cross section with obstruction is derived
from the initial roughness of the whole cross section, depending on
whether there is either a single or composite roughness or based on the
type of roughness of the bottom and sides;
- The variation of the weed factor during a certain period will depend
on the type of maintenance. Maintenance activities in view of the
weed growth are referred to by an obstruction degree. The effect of
maintenance on the roughness is expressed by:
•

ideally maintained: negligible obstruction degree over time;

• well maintained: a maximum obstruction degree of 10% is assumed;

•

poorly maintained: more than 75% obstruction degree is assumed;

•

the actual roughness is calculated by using the weed factor F w .

6.1.5 Input and output data

Input data
For the computation of the water flow and sediment transport, the program
requires several types of input data, which include:
- Simulation period : the characteristics of the irrigation season include:
• number of periods in which the irrigation season is divided;

• type of maintenance to be expected during each period of the

irrigation season;

number of days for each period and the number of irrigation hours
per day.
- Canal dimensions : the geometrical dimensions of main and secondary
canals contain:
•

•

for each canal section: the number of sections, type of roughness
(de Chézy, Manning or Nikuradse);

• for each canal section: the location from the upstream boundary,

length, side and bed slope, width and elevation of the bottom;
roughness coefficient.