Medieval Muslim scientists often focused on practical matters, particularly hydraulic engineering, as water was always a precious resource in the arid lands where Islam traditionally flourished. Engineers designed various kinds of water-raising machines, some powered by animals, others powered by rivers and streams. The waterwheels along the Orontes River in Syria were used to irrigate until modern times. Watermills were used to grind corn and other grains, though in Iran water power was often supplemented or replaced by wind.
Bridges and dams were needed to channel water. In addition to the standard beam, cantilever and arch bridges, engineers also designed bridges of boats to span rivers. Dams were widely used to divert rivers into irrigation canals. Perhaps the most ingenious hydraulic technologies were the distribution networks of canals and qanats, subterranean aqueducts that sometimes carried water for hundreds of miles. Cisterns and underground ice-houses were used for storage. Various instruments were used to measure water flow, and the Nilometer built in 861-62 still stands on Rawda Island in Cairo.
In addition to these machines and technologies related to water, Muslim engineers also designed several types of siege engines, notably the traction and the counterweight trebuchet. Their ingenuity is clear from the many kinds of fine machines they also perfected, ranging from clocks and automata to fountains. Some were meant for practical purposes but others were designed for amusement or aesthetic enjoyment, and their components and techniques were of great importance for the development of machine technology.