There are 91 working locks on the Canal du Midi along its course from the Bassin du Thau on the Mediterranean coast to the junction with the Canal lateral a la Garonne in Toulouse. There are a further 13 locks on the La Nouvelle branch which runs through Narbonne to the Mediterranean at Port-la-Nouvelle. The locks are all under the management of the French navigation authority, Voies navigables de France.
Construction
The Canal du Midi was built between 1666 and 1681 by Pierre-Paul Riquet to provide an inland water route through Southern France between the Atlantic at Bordeaux and the Mediterranean at Sète via the Garonne. The first design for the locks on the canal was a rectangular shape however due to a collapse of a side-wall early in the building program (exactly which lock is not recorded), Riquet modified his plans and rebuilt both existing and new locks with an ovoid chamber. They were typically 11 m wide at the midpoint and 6 m at the gates with an overall length of 30.5 m. Riquet also restricted the maximum rise to 2.9 m so whereas previously he would have built one deep lock he instead used intermediate gates creating double, triple and sometimes quadruple chambers. During the Canal du Midi modernisation program of the 1970s several of these multiple chambers were converted into single "deep" locks with concrete side walls.
The lock gates were originally made of oak in the traditional mitre pattern with balance beams and each gate had a single large wooden sluice drawn up by a vertical screw. The introduction of electric and hydraulic systems for both the lifting of the sluices and the opening of the gates has seen the removal of the balance beams and modern gates are of metal construction.
At each lock there is a double-fronted two-storey lock keeper's house upon which is fixed either a cast iron or a masonry sign showing the name of the lock and the name and distance to the adjacent locks in each direction. The locks are still operated by lock keepers and passage is only possible when they are in attendance however on La Nouvelle branch operation by boaters is allowed. The locks are open every day except 1 January, 11 November and 25 December, from 08:00 until 17:30 out of season and 08:00 until 19:00 in the summer peak; all locks are closed 12:30 – 13:30 for lunch.
Profile At its western end, Toulouse, the canal is at an altitude of and climbs to at its summit level between Ocean Lock and Mediterranee Lock west of Castelnaudary before dropping down to sea level at Sète. The graph shows the profile of the Canal du Midi from Toulouse (1), through the summit of the canal at Seuil de Naurouze (2), Castelnaudary (3), then Carcassonne (4) and Trèbes (5). The channel continues to Béziers just after Fonsérannes Lock (6), and then on to Agde (7) before flowing in to the Bassin de Thau at Sète (8).
At , Naurouze is the highest point of the canal with a drop of between the summit and Toulouse and between the summit and Sète. The longest pound is between Argens Lock (Aude) and the Fonsérannes Lock (Hérault) while the shortest reach is between two locks at Fresquel.René Gast, Le canal du Midi et les voies navigables de l'Atlantique à la Méditerranée, éditions Ouest-France, 2000, , p. 22
Locks
The following list numbers the locks from the Canal lateral a la Garonne in the west to the Bassin du Thau in the east. Staircase locks are listed as a single entity but the number of individual chambers in the flight is noted. Travelling west to east from Toulouse to Sète the locks numbered 1–18 are ascending and 19–86 are descending. Castanet lock is the first lock with an elliptical chamber, as Riquet realised it was the best fit solution due to mechanical stress from surrounding areas.
Locks in the Canal du Midi Locknumber Lock name Coordinates(links to mapsand satellite images) Number ofchambers Distancefrom Toulouse(km) Image Altitude(metres)1 Béarnais Lock 11.1135m2 Minimes Lock 12139m3 Bayard Lock 13.6145m4 Castanet Lock 115.7 148m5 Vic Lock 117.4151m6 Montgiscard Lock 124.9 155m7 Aygues-Vives Lock 128.1 159m8 - 9 Sanglier Lock 229.6 163m10Négra Lock 133.3 166m11 - 12Laval Lock 237.5 170m13Gardouch Lock 138.9 173m14Renneville Lock 143.0 176m15 - 16Encassan Lock245.9 185m17Emborrel Lock147.5 189m18 Océan Lock 151.6 193m 51.5 Summit (Seuil de Naurouze) 52 193m19Méditerranée Lock 156.6 193m20-21Roc Lock 257.5 189m22 -24Laurens Lock 358.7 180m25Domergue Lock159.7 175m26Laplanque Lock160.9 173m27 - 30Saint-Roch Lock 465.4 170m31 - 32Gay Lock 267.1 159m33 - 35Vivier Lock 368.7 154m36Guilhermin Lock 169.1 147m37Saint-Sernin Lock 169.7 145m38Guerre Lock 170.6 141m39Peyruque Lock 171.7 139m40Criminelle Lock 172.2 137m41Tréboul Lock 173.6 134m42Villepinte Lock 177.4 130m43Sauzens Lock 179 127m44Bram Lock 180.3 126m45Béteille Lock 185.9 123m46Villeséquelande Lock 193.4 122m47 - 48Lalande Lock 298.2 116m49Herminis Lock 198.5 114m50Ladouce Lock 199.9 109m51Carcassonne Lock 1105.5 106m52Saint-Jean Lock 1108.0 102m53 - 54Fresquel Double Lock 2108.8 97m55Fresquel Single Lock 1109.0 92m56Evêque Lock 1112.6 91m57Villedubert Lock 1113.4 86m58 - 60Trèbes Lock 3118 84m61Marseillette Lock 1127.2 79m62 - 64Fonfile Lock 3130.4 76m65 - 66Saint-Martin Lock 2131.6 67m67 - 68Aiguille Lock 2133.4 59m69 - 70Puichéric Lock 2136.4 57m71Jouarres Lock 1142.7 49m72Homps Lock 1146.4 46m73 - 74Ognon Lock 2147.1 41m75 - 76Pechlaurier Lock 2149.8 38m77Argens Lock 1152.3 32m78Fonserannes Lock 6 (+2 unused)206.6 32m79Orb Lock 1208.0 12m80Béziers Lock 1208.4 81Ariège Lock 1212.5 9m82Villeneuve Lock 1213.8 6m83Portiragnes Lock 1218.3 5m84Agde Round Lock 1231.4 4m85Prades Lock 1232.93m86Bagnas Lock 1235.3 2m
See also Aqueducts on the Canal du Midi Water features on the Canal du Midi
Notes Lock numbers are as given in the appendix of the 1994 edition From Sea to Sea by L.T.C. Rolt The flight at Fonserannes was "replaced" by a water slope in 1984 hence the single "lock number". However, the slope has never worked and the 6 flight staircase remains the only way to pass through meaning that there are 91 locks but only 86 numbers. Chamber has three sets of gates, the third being the junction with the branch descente dans l'Hérault
References