Oued Fes
[1][2] Over the centuries the river has been split and diverted into a multitude of canals that distributed water across the city and once powered a number of historic waterwheels.
[1][3] These various water channels converge into the Oued Bou Khrareb which runs through the middle of the old city and historically divided the Qarawiyyin and Andalusiyyin quarters.
The river begins at Ras al-Ma ("Head of the Water"), 12 kilometres southwest of the city, from a hollow of lacustrine limestone, with an approximate flow of 500 litres/second.
[1] It once passed through a flat area of marshes and wetlands located near what is now Fes el-Jdid and the modern Ville Nouvelle, before emerging at a number places.
[1] Much of the Oued Bou Khrareb's course, from Bab Jdid to Place R'cif, is now hidden beneath a modern road for car traffic (one of the few that penetrates the medina).
[4] This division creates a number of canals (most of them subterranean) through Fes el-Bali which eventually spill back into the Oued Bou Khrareb (the name of the river's main course inside the city).
[4][1] Just after it enters the city walls, the water of the Oued el-Lemtiyyin is collected by a large distributor structure located adjacent to the south side of Bab Bou Jeloud gate.
[7] It has three arched openings that lead into vaulted chambers under the wall from which the water then emerges on the other side into three open-air channels or "zones", located at different elevations.
The two other zones, located on higher ground on either side of this, received lesser amounts of water but were more complex, consisting of multiple small basins and channels that regulated the distribution into local neighbourhoods.
[1]: 113 Many of these historic canals are now underground, with only some ancient toponyms hinting at former bridges that passed over them (e.g. the name Qantrat Bou Rous along a part of Tala'a Kebira).
[1][3] The Oued Bou Khrareb is crossed by several historic bridges inside the medina, some of which were first built before the unification of the two shores into a single city in the 11th century.
[1]: 142–146 Traditionally, the three most important bridges were those of Bin el-Mudun, Terrafin, and Sidi al-'Awwad, each of which were located along a major thoroughfare of the Andalus quarter (the eastern shore).
The Bin el-Mudun Bridge, believed to date from the time of Dunas ibn Hamama, was considered one of the most picturesque, being located amidst a stretch of rocky rapids.
[8][9] The Terrafin or al-Tarrafin bridge,[8][3] originally named Qantrat Bab al-Silsila,[3] is found on the northern edge of Place R'cif.
It is also believed to date initially from Emir Dunas in the 11th century,[8][9] while María Marcos Cobaleda and Dolores Villalba Sola attribute it to the Almoravid period as well.
[3][1]: 336 The river, particularly the Oued Bou Khrareb within the old medina, has long suffered from heavy pollution due to sewage, the activities of the nearby tanneries (which generate chemical waste), and to being sometimes used as a dumping ground by residents.
[11][12] The waste of the tanning industry and other activities also led to toxic chemicals, particularly high levels of Chromium, accumulating in the soil and the water.
[12] Although it is believed that this does not affect the city's drinking water (which comes from upstream), it creates problems for sites downstream along the Sebou River following its confluence with the Oued Fes.
