Were it not for these dams steamers might reach Mosul itself, at an elevation of 353 ft.
Two great dams on the river (one built by the Federal government) provide good water power.
Throughout Great Britain there are still many reservoirs, with earthen dams, which cannot safely be filled; and others which, after remaining for years in this condition, have been repaired.
The wheels, called naoura, are of the most primitive construction, made of rough branches of trees, with palm leaf paddles, rude clay vessels being slung on the outer edge to catch the water, of which they raise a prodigious amount, only a comparatively small part of which, however, is poured into the aqueducts on top of the dams. These latter are exceedingly picturesque, often consisting of a series of well-built Gothic arches, and give a peculiar character to the scenery; but they are also great impediments to navigation.
It is lowest in November, and rocks, shallows, and the remains of old dams then render it almost unnavigable.