Conveyance, distribution and management structures

Conveying water to the field requires similar structures to those found in major canal networks. The conveyance itself can be an earthen ditch or lateral, a buried pipe, or a lined ditch. Lined sections can be elevated as shown in Figure 8, or constructed at surface level. Pipe materials are usually plastic, steel, concrete, clay, or asbestos cement, or they may be as simple as a wooden or bamboo construction. Lining materials include slip-form cast-in-place, or prefabricated concrete (Figure 9), shotcrete or gunite, asphalt, surface and buried plastic or rubber membranes, and compacted earth.

The management of water in the field channels involves flow measurement, sediment and debris removal, divisions, checks, drop-energy dissipators, and water level regulators. Some of the more common flow control structures for open channels are shown in Figure 10. Associated with these are various flow measuring devices like weirs, flumes, and orifices. The designs of these structures have been standardized since they are small in size and capacity. Designs for flow measurement and drop-energy dissipator structures need more attention and construction must be more precise since their hydraulic responses are quite sensitive to their dimensions.