The construction work for the Canal du Midi entrusted by King Louis XIV to Pierre-Paul Riquet was officially completed in 1684. But soon after, it became necessary to make some improvements to the original design.
The most significant modifications were decided upon after an inspection carried out by Vauban. From 1685, sand deposits were quickly increasing in the canal and navigation taxes were not enough to compensate the cost of maintenance. The King therefore asked Vauban for recommendations of how to improve Pierre-Paul Riquet's creation.
The projects involved in Vauban's consolidation work were managed by Antoine de Niquet from 1686 to 1694, the date upon which the Canal du Midi was considered to be actually completed.
Numerous structures were built to separate the waterways crossing paths with the canal (aqueducts) and to evacuate excess waters (spillways). Vauban also managed to ensure a more regular water supply. He had the Cammazes tunnel built, which was then named after him (Voûte Vauban), to extend the Rigole de la Plaine channel. He also strengthened Saint-Ferréol dam and increased capacity there.
In the late 18th-early 19th century, another series of consolidation work brought about some significant changes. The main ones being the addition of the side canals to the Canal du Midi.
The construction of the Canal Saint-Pierre (or Canal de Brienne) in Toulouse provided a link between the Garonne river and the canal, via the Port de l’Embouchure. The Canal de Brienne made the connection to the Garonne upstream from Toulouse much easier.
Opening of the Canal de Jonction and Canal de la Robine in Narbonne.
In September 1787, the connecting canal between the Canal du Midi and the river Aude (in Sallèles d’Aude) was opened to navigation. From there, it was then possible to sail to Narbonne or even Port La Nouvelle via the restored Canal de la Robine.
The Lampy-Neuf reservoir was created in the Montagne Noire region, to provide the canal with an extra supply of water, deemed necessary to ensure navigation on the Canal de Jonction (1777-1782).
Construction and opening of the route around Carcassonne.
When the Canal du Midi route was being studied, Riquet put forward the idea of the canal passing under the city walls to the consuls of Carcassonne. But the additional cost had to be covered by the municipal budget and so the local authorities rejected this idea.
A century after Riquet's proposal, in a worsened economic context, the consuls looked into the creation of an alternative route, around the city. Construction work began in 1787, and was then suspended in 1789. It started again in 1798 and was completed in 1810. The Iéna trench, the port of Carcassonne and Fresquel aqueduct are some iconic creations included in this project.
Riquet's route through the Fresquel valley was therefore abandoned. There are still some traces of this section today such as the former Port de Foucaud and the Arnouze aqueduct.
The owner, the Compagnie du Canal du Midi, made some investments to improve navigation conditions on the canal and increase boat speed.
These improvements included a windlass at the lock gates to help open sluices, and adjustments of bends. To make trade easier, new port areas were created, including new shops.
A special civil engineering service was called upon to study the ways of improving the transport of goods along inland waterways between Toulouse and Bordeaux. Navigation along the Garonne river was often dangerous both for the boats and crew.
There were regularly extreme fluctuations in the river water level which hampered trade. Jean-Baptiste de Baudre, chief engineer for civil engineering based in Agen, proposed the creation of a canal that would run alongside the river, so that boats could sail here in any season.
The Canal de Garonne was built as an addition to the Canal du Midi between Toulouse and Castets-et-Castillon in Gironde (193 km). The canal was built section by section and the management of the waterway was entrusted to the 'Compagnie des Chemins de Fer du Midi et du canal latéral à la Garonne', created in 1852.
When the Canal de Garonne was inaugurated in 1856, Riquet's dream of linking the two seas had come true. The unpredictable waters of the Garonne could be avoided, and safe navigation was now possible all the way to the Atlantic.
In light of the development of the railroad, it was necessary to make some improvements to the Canal du Midi to ensure that waterway navigation would remain profitable.
New engineering structures to resist competition from the railroad.
In 1852, the 'Compagnie des Chemins de Fer du Midi' was established. This company built the railroad network between Bordeaux and Sète. The railroad was inaugurated in 1857, and would immediately compete with the Canal des Deux Mers. Consequently, the Compagnie du Canal du Midi had several engineering structures built to make navigation easier, particularly when crossing the Orb (Béziers), Libron (Vias) and Hérault (Agde) rivers.
The Ouvrages du Libron structures were designed in Vias by Urbain Maguès (1855-1857). This is a set of mobile aqueducts that allow the waters of the Libron river to cross over the canal when the water levels are high. The Orb aqueduct in Béziers, a creation from Urbain Maguès and Achille Simoneau (1854-1857) allows boats to avoid a dangerous section of the Orb river. For the Hérault river, new structures were installed on the riverbed.
In 1858, the 'Compagnie des Chemins de Fer du Midi' was entrusted the management of the canal and introduced a pricing policy that favoured rail transport, and so led to the decline of the waterway.
Major modernisation work began on the Canal du Midi in an effort to make the canal more competitive in the face of rail transport. This work was brought to a halt upon the outbreak of the First World War and was then only partially resumed in the 1930s, to be resumed once again in the early 1960s. The first part of the modernisation work was undertaken on the Canal de Garonne.
The last significant work was the modification of the locks in accordance with the Freycinet gauge, which involved lengthening the locks by 10 m so that freight barges (péniche barge) could pass through (38.50 m, 350 tonnes). The work began in 1977 on the east side of the Canal du Midi and around Toulouse, but was suspended in 1984 by the French Ministry of Development due to the economic crisis France was experiencing. This work was only completed on three sections at either end of the canal: Toulouse-Ayguevives; Béziers-Thau lagoon; Jonction and Robine in Narbonne.
Did you know?
When the Freycinet project was abandoned, this meant the locks of the Canal du Midi from Sanglier lock to the Argens-Minervois lock (140 km) were left intact. In this section, the locks are still the same size as in the 17th century.
In the 1990s, the water supply system to the Canal du Midi was modernised. The work was done to significantly optimise water management. For example, automated gate-operating mechanisms allow much more precise management of water volumes. This also means that instream flows can be controlled, to make sure that rivers have the necessary flows for aquatic species or water-dependent species. Automated machines also calculated the total flows passing through.
At the end of the 1990s, Voies Navigables de France (VNF) began introducing mechanical and electric mechanisms on the canal locks. Manual mechanisms were replaced with electric motors. The sluices and gates were mechanically operated. They were opened using electric motors and hydraulic cylinders. The lock keeper used a control panel or a mobile console to trigger mechanisms.
Since 2010, some of the locks on the Canal du Midi have been automatic, equipped with a control panel so that skippers can pass through the locks independently. VNF employees monitor the locks and are on-hand to assist if needed.
Over the past few years, work has been done to optimise the management of water. The goal is to be able to monitor the flows, the water levels in the canal pounds, take samples and monitor the main outflows. Work is also being done to ensure the locks are watertight.
For the past ten years or so, Voies Navigables de France (VNF) has been using new technologies in computer-aided maintenance management to monitor the condition of the facilities, prevent malfunctions and deal with any faulty equipment.
The staff use digital tablets on a daily basis to input and process data, which is then used to establish annual programmes for preventive maintenance.
Additionally, VNF's plan to provide assistance for modernisation and innovation on a national level includes centralised control stations. In the future, these stations will be used to simultaneously control several locks remotely, optimise traffic flow and for better hydraulics management of the network thanks to real-time processing of data.