From the eighth century onwards, Muslim societies extending from Cordoba in Spain to Damascus, Baghdad, Fez and through to Marrakech, relied on the world’s most advanced water technologies at the time to serve their communities. Curved dams, de-silting sluices and hydropower were amongst the innovations at the time at the disposal of Muslim engineers [1,2].
One prominent inventor who left a lasting legacy was Al-Jazari, born in the twelfth century. In Diyarbakir in upper Mesopotamia (now present-day Turkey), Al-Jazari invented a splendid array of water-raising machines, five of which are described in his great book on machines  completed in 1206 and regarded as a groundbreaking text in the history of technology
One of Al-Jazari’s water-raising machines known as the na’ura (noria) is a historically very significant machine. It consists of a large wheel made of timber and provided with paddles. The large-scale use of norias was introduced to Spain by Muslim farmers and engineers. The noria of Albolafia in Cordoba, which still stands today served to elevate the water of the river up to the palace of the Caliphs. Its construction was commissioned by Abd Al-Rahman I, and it has been reconstructed several times.
Perhaps the most astonishing of Al-Jazari’s inventions was the water-driven twin-cylinder pump. An important feature was its double-acting principle, the conversion of rotary into reciprocating motion, and the use of true suction pipes. Al-Jazari’s twin-cylinder pump could be considered as the origin of the suction pump, and not that of Taccola (c.1450) as is commonly thought . Corn-milling using water power was an essential part of economic life and some Muslim technologists are known to have looked upon a river in terms of the number of mills it could turn .
Places noted for the number of water mills included Nishapur in Khurasan (Iran), Bukhara (Uzbekistan), Fez (Morocco), Tlemcen (Algeria) and the Caspian province of Tabaristan. In tenth century Palermo, then under Muslim rule, the banks of the river below the city were lined with mills and there are also many references to mills in the Iberian Peninsula  (e.g. at Jaen and Merida).
A variety of methods were used to increase stream flow rates that powered the mills and thus increasing productivity. Where feasible, water wheels were often installed between the piers of bridges where streamflow was accelerated due to partial damming of the river.
A particularly impressive innovation was the ship-mill, used widely in the Islamic world to harness the power of the faster currents at midstream, which also avoided the problem of low water levels facing fixed mills during dry seasons. It is known ship-mills were used in Murcia and Zaragoza in Spain, Tiblis in Georgia and in Upper Mesopotamia where they were quite formidable. Writing in 988, the geographer Ibn Hawqal reports  that the ship-mills on the Tigris at Mosul had no equal anywhere. They were very large, constructed of teak and iron and positioned in very fast currents, moored to the river bank by iron chains. Similar mills were also located at other places on the Tigris and on the Euphrates. The average mill had the capacity to grind around 10 tonnes of grain over 24 hours, enough to feed 25,000 people . Innovation did not cease there, there are accounts of tidal power being harnessed in tenth century Basra which is at least a century before their adoption in Europe .
Both surface water and groundwater resources were utilized to establish some of the most sophisticated irrigation systems known at the time. For example, Muslim irrigation systems, with their associated hydraulic works and water-raising machines remained the basis for Spanish agriculture and were transferred to the New World. After the 15th Century, Muslim inspired techniques were adapted in the Canary Islands and as far away as Texas and Louisiana, partly to irrigate thirsty sugarcane fields. In France, Provencal engineers in the 11th to 13th centuries copied Islamic irrigation networks, and some of them are still in use today . The qanat, a gravity fed water supply system consisting of an underground tunnel connected to the surface by a series of shafts, was widely adopted across the arid parts of the Muslim world and as far a field as Xianging province in China .
Despite increasing knowledge of the achievements of Muslim water innovators, it is likely that much remains unexplored and it is speculated that amongst the thousands of Arabic manuscripts lying untranslated and often uncatalogued in libraries across the Middle East, Europe and North America, there may be countless examples of water management practices and technologies implemented in the Muslim world up until the 16th Century and possibly beyond .
The future of water supply in the Middle East and beyond is set to become transformational if the curiosity, ambitions and enthusiasm of some of the early innovators are embraced. Looking to the sea, as had the engineers of Basra a millennia ago, will be the key to a region faced with the prospect of crippling water scarcity in future years.
Many parts of the world (including the Muslim world) currently facing water shortages that are likely to become exacerbated in future, are also blessed with coastlines and ample sunshine. This is a perfect recipe for some truly remarkable desalination methods to be developed that could harness the power of renewable energy including solar and tidal. Seas are a generally a reliable and sustainable source of water; they are vast, do not dry up, are less polluted than rivers, and have built-in circulation systems, which make them a more attractive source of water than inland, saline aquifers.
Desalination usually involves removal of salt from seawater using either thermal distillation or membrane separation. The most widely-used desalination techniques are: Reverse Osmosis (RO) and Multistage-Flash (MSF) distillation. Although the capital and operating costs of these techniques have been significantly reduced during the last 40 years, due to innovations and advancement in technologies, these techniques still have major practical limitations, resulting in high operating and capital costs, which make their use less affordable by many nations.
The most widely-used desalination processes are driven almost entirely by the combustion of fossil fuels, i.e., direct, thermal methods, such as MSF, and/or indirect, membrane-based methods, such as RO (using electricity generated by fuel-fired power plants).
Current desalination costs are estimated to be between $1.0-2.0 per cubic meter of produced fresh water for large-scale applications, though actual costs are higher for older plants and fuel-powered plants. The breakdown of these costs shows that about 50% of the operating cost is accounted for by energy .
Current world efforts in the area of desalination are focusing on increasing the energy efficiency of desalination processes, and significantly reducing the dependence on an energy- short world, by using alternative energy sources [10,11]. Alternative energy sources, including solar, wind, tidal and osmotic types of energy, could provide secure, sustainable, adequate and affordable energy sources to drive desalination technologies.
A world pioneer in this field is demonstrating that a re-emergence of Muslim innovators is already underway. Adel Sharif, winner of the prestigious British Royal Society Brian Mercer Award in 2005  is leading the way. An academic at the University of Surrey (UK), he has written extensively on the topic [13-19].
He points out that the Muslim World, including many other parts of the world that have or may have water shortages, are known to have dry climates and long, sunny days throughout the year. Therefore, the use of solar energy and, in particular, its direct use in desalination and water treatment should be strongly encouraged. He also goes onto state that on the humanitarian dimension, UN Statistics indicate that around 1 billion people today lack sufficient, clean water. If just a small proportion of the three million lives lost each year can be prevented, then something of global importance will have been achieved.