ABSTRACT
Natural rivers and man-made canals are open channels. They have many advantages over pipes and have been used for many centuries for water supply, for transport and for agriculture. The Romans made extensive use of channels and built aqueducts for their sophisticated water supply schemes. Barge canals are still an important means of transporting heavy bulk materials in Europe and irrigation canals bring life and prosperity to the arid lands of North Africa, Middle East, India and Australia as they have done for thousands of years.
