| Thouet | |
|---|---|
 | |
   | |
| Location | |
| Country | France |
| Physical characteristics | |
| Mouth | |
• location | Loire |
• coordinates | 47°16′47″N0°6′38″W / 47.27972°N 0.11056°W /47.27972; -0.11056 |
| Length | 142 km (88 mi) |
| Basin size | 3,396 km2 (1,311 sq mi) |
| Basin features | |
| Progression | Loire→Atlantic Ocean |
TheThouet (French pronunciation:[twɛ]) is a tributary of theLoire in theNouvelle-Aquitaine andPays de la Loire regions of westernFrance. The Thouet rises atSecondigny, close to the source of theSèvre Nantaise, and joins the Loire just to the west ofSaumur. It is 142.6 km (88.6 mi) long,[1] and drains an area of 3,396 km2 (1,311 sq mi).[2]
The river's name derives from the ancientGallic word for tranquil.[3]
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The Thouet rises in theGâtine Vendéenne, the most southern outcrop of theArmorican Massif, at 225 metres (738 ft) altitude. The Armorican Massif is made up ofvolcanic andmetamorphic rocks dating back to thePaleozoic era. This impermeable land does not result in any importantaquifers but is an area of significant rainfall runoff. From the source toParthenay the river flows in a generally east–west direction.[4][5]
To the east of Parthenay, the river turns north and flows on a generally northward heading for the rest of its course. BetweenSaint-Loup-Lamairé andThouars, the river flows onto theParis Basin, an area ofsedimentary rocks where successive marine deposits of periods from theTriassic to thePliocene were laid down. The nature of the rocks here allows the formation of an aquifer whose water reserves support the river in times of low flow.[4][5]
In order downstream, the Thouet flows through:[3][4]
The principaltributaries of the River Thouet are:
For much of its length, the Thouet is paralleled by theGR 36long-distance walking route, which connectsOuistreham, on the coast of theEnglish Channel, withBourg-Madame, on the border withSpain. This stretch of the path traces the footsteps ofpilgrims fromBrittany andNormandy on their way toSantiago de Compostela, and in places crosses the river using the samefords,packhorse bridges andstepping stones the pilgrims would have used.[3][6]
The Thouet was once navigable between its confluence with the Loire and Montreuil-Bellay. The first mention of navigation on the river dates from 1430 when an assembly of merchants in Saumur suggested the creation of a navigation over this stretch of the river, requiring the creation of passages through threemill weirs. It is possible that boats were already carrying goods on the river before that date, the cargo being transferred between boats at each obstacle.[7]
King Charles VII authorised the start of work byletters patent, financing the work by allowing the lords of Montreuil-Bellay to raise a tax on wine that would pass through their land. In the 15th and 16th centuries, the passage through the weirs probably took the form offlash locks. The laterpound lock may have been introduced towards the end of the 16th century, and it is known that three pound locks were in use on the river by 1608. A project to make the river navigable up to Thouars was proposed in 1746 but was never executed.[7]
TheDive, a tributary of the Thouet, was canalised in 1834 to create theCanal de la Dive. As part of this development, two modern pound locks with straight sides and mitred gates were built on the Thouet, downstream of the confluence with the Dive. A third modern lock was built at the same time on the Thouet, but upstream from the confluence of the Dive. These locks had dimensions of 32 m (105 ft) length, 5.20 m (17.1 ft) width, and a draught of 1.60 m (5 ft 3 in).[7]
However the new navigation soon faced competition from better roads and the railway, which appeared in the region in 1874. The maximum boat size imposed by the locks proved insufficient, and a proposed enlargement to the largerFreycinet gauge was never realized. The last commercial navigation on the river was in 1920.[7]
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