The comparative scantiness of its sources, the steepness of its upper course and the rapid evaporation which takes place after the short rainy season would make the Senegal an insignificant stream for more than half the year; but natural dams cross the channel at intervals and the water accumulates behind them in deep reaches, which thus act as reservoirs.
The Monongahela has been improved by locks and dams to Fairmont.
South of Mosul, at which point navigation is blocked by two ancient dams, erected, apparently, to control the river for the Assyrian city of Calah, the ruins of which are called Nimrud by the natives after these dams, which they conceive to be the work of that mythical hero.
Were it not for these dams steamers might reach Mosul itself, at an elevation of 353 ft.
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.
The experiment was so far successful that, with incredible difficulty, the two vessels did actually reach Meskene, but the result of the expedition was to show that practically the river could not be used as a high-road of commerce, the continuous rapids and falls during the low season, caused mainly by the artificial obstructions of the irrigating dams, being insurmountable by ordinary steam power, and the aid of hundreds of hands being thus required to drag the vessels up the stream at those points by main force.
Midhat caused many of the dams to be destroyed and for some years occasional steamers were run between Meskene and Hillah in flood time, from April to August.
From Tewkesbury; the locks from Evesham upward to Stratford (17 m.) are decayed, but the weirs, and mill-dams still higher, afford many navigable reaches to pleasure boats.
It is irrigated by an elaborate system of dams, cuts and canals in connexion with the rivers Cauvery and Coleroon, and the soil is exceedingly productive.
Two great dams on the river (one built by the Federal government) provide good water power.
The improvement of the river, by the removal of snags and the construction of dams and locks in order to give it a navigable depth of to ft.
I built dams of pebbles, made islands and lakes, and dug river-beds, all for fun, and never dreamed that I was learning a lesson.
A factory-owner, hearing what depth I had found, thought that it could not be true, for, judging from his acquaintance with dams, sand would not lie at so steep an angle.
The remains of Langeron's and Dokhturov's mingled forces were crowding around the dams and banks of the ponds near the village of Augesd.