1) Canals are artificial channels constructed to carry water from a source like a river or reservoir to agricultural fields. 2) Canals are classified based on their water source (permanent or inundation), function (irrigation, navigation, power), alignment (watershed, contour, side slope), discharge (main, branch, distributary), and whether they have lining. 3) The cross-section of a canal includes components like side slopes, berms, freeboard, banks, and may involve partial cutting and filling to achieve a balancing depth.