Abstract:
Canal design is perhaps the simplest and most common amongst Irrigation Engineers. With a Iarge number of irrigation projects constructed in the world, the design of canals is well known.
Design of canal depends on discharge, topography, inner side slopes lined and unlined, operation and maintenance.
Following are important aspectsin a canal
(i) Silting
(ii) Scouring/non scouring
(iii) Weed growth
(iv) Maximum permissible velocity
(v) Minimum and maximum bed slopes
(vi) Operation and maintenance cost
(vii) Seepage losses
(viii) Cost economics of canal section
_ - There are a number of design practices and it is not that simple as is being practiced.
The design of lined canals particularly trapezoidal canals is largely done by trial and error by arbitrarily choosing the bed width depth ratio (B:D). This resulted many times uneconomical section. Also their operational performance have not been as was expected in designed lined canals. These canals have also shown considerable sign of damage to lining, seepage, silting, weed growth, and low discharging capacity.
Best hydraulic sections are most economical as long as the cost of earth work (excavation and embankment) is less than the cost of lining per unit length of channel and this is the most usual case. These sections, besides having least area and perimeter also have minimum top width. Therefore land width required is also minimum, in comparison to other wide sections.
