Dams, power stations, bridges : the Loire and Allier rivers
are doted with all kinds of hindrances which delay or prevent the migration
of the last Atlantic salmons. The map below shows the main obstacles but,
as you may guess, it is incomplete : small dams are very numerous. We
must also remember that organic and chemical pollution as well as the
million ton of slime in the estuary - the « muddy cork »-
form a major obstacle to salmon migration.
- 1. The riffle of the Wilson bridge in Tours
is daming the Loire river. This riffle was caused by the over-extraction
of gravels in the river bed.
- 2. The fish ladders of the mobile dam of Blois
(built in 1969) have never worked. Since 1983, the floodgates are only
opened in summer, which may prevent late migrations.
- 3. 65 m3/s are diverted from the Loire river
to cool the reactor of the St-Laurent-des-Eaux nuclear plant. This hinders
young salmons on their way to the sea in springtime.
- 4. The Dampierre nuclear plant can be easily
passed by salmons thanks to an opening on the right bank but the water
level has to be high enough.
- 5. The Belleville nuclear plant is more and
more difficult to pass because of the deepening of the river bed caused
by extraction of gravels. It is however equipped with two fish ladders.
- 6. Decize dam.
- 7. Maisons-Rouges. This dam had been obstructing
the Vienne river since the beginning of the century. Numerous spawing
grounds (a fifth a the whole Loire basin) were not accessible It has
been demolished in november 1998. A first salmon has been observed upstream
this point in august 1999 !
- 8. The Guétin « bridge-channel
». The first obstacle for salmons on the Allier river. It is 1,5
m high and is easily passed.
- 9. The Lorrains dam.had been built in 1840 and
was modernized in 1950. It is not high and does not create any problems.
- 10. In Moulins, the Allier river flows under
the Règemortes bridge.that becomes unpassable when the water
level is low.
- 11. The « dam bridge » of
Vichy had long been a obstacle for salmon migration. It is now much
more easy to pass thanks to improvements made according to the «
Plan Loire Grandeur Nature ».A fish ladder, equipped with an observatory,
has been built. People can now watch salmons and other migratory fishes
on their way upstream.
- 12. Madeleines. This small obstacle is easily
passed by salmons.
- 13. Villerest dam. It is 70 meters high and
is totally unpassable. The reservoir water is seriously eutrophic.
- 14. The Vezezoux dam, which was previously used
by the thermal power station of La Taupe had not been equipped with
fish ladders. It is very difficullt to pass in spite of a small breach
on the left bank.
- 15. The Bajasse dam was built in 1312. It is
used for leisure purposes and is equipped with an efficient fish ladder.
- 16. Grangent dam.This EDF (National Electricity
Company) building is 70 meters high. It is totally unpassable and has
drowned wonderful gorges of the Loire river. More than a million ton
of toxic mud has been accumulated behind the water gates so that the
draining is very difficult.
- 17. The small power plant of Vieille-Brioude
and the Lavoûte-Chilhac dam are private dams which are about 2
meters high. They are not equiped with fish ladders and constitute a
- 18. The small power-station of Langeac was built
in 1991.It is equipped with a disfonctional fish ladder.
- 19. Poutès-Monistrol hydroelectric power
station.This is the most controversial obstacle. It is responsible for
90% of the loss of Atlantic salmon in the Loire and Allier river. Fifty
two years after it was built, it has been equiped with a fish ladder
next to the Monistrol factory and of a slide for young salmons on the
dam itself. It is also in 1993 that the minimun authorized flow has
been raised to 2,5 m3/s, which gives more chances to salmons to reach
the spawning grounds.
- 20. St-Etienne du Vigan hydroelectric dam. Built
at the end of last century, it has prevented the migration towards the
best spawning grounds of the Allier river. It has been destroyed in
June 1998 as a part of the « Plan Loire Grandeur Nature ».
- 21. Ten kilometers upstream the St-Etienne du
Vigan dam, the Naussac 2 dam has been recently built. It costed 300
million french francs, pumps 100 million tons of water each year to
inject it in the Naussac reservoir, which contributes to throw the upper
Allier water pattern out of balance.
- 22. Lapalisse dam. This hydroelectric complex
pumps water in the Loire river.for turbines and then sends it to the
Ardèche river. It thus maintains a minimal water level in this
river and enables an intensive practice of canoeing in the Ardèche
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