Salmon & Dams



salmon_runs.jpg**danny p

Il s'agit d'un tableau sur les statistiques de capture de ces dernières années datant de 1870 à 1990.**


Ce barrage est à 50 miles d'Okanogan. Barrage de Grand Coulee, est situé sur le fleuve Columbia, et bloque maintenant une des plus grandes montaisons de saumon en Amérique du Nord. danny p


This dam is in Southern France. Dams destroy fauna and flora.
It is an artificial lake.


Cette carte illustre l'ensemble des barrages dans la partie nord-ouest de l'Amérique. danny p


Salmon and Dams
Salmon and Dams
Dams were built to produce electricity through power created from the force of the flow of water.
It is therefore an artificial lake upstream from which water flows, turning the turbines in the dams. There are many consequences of creating dams.
By creating this artificial lake, we destroy the lives of animals and plants; the downstream part of the rivers empty and the fish die or migrate.
Unfortunately salmons breed upstream. Dams block passages to upstream parts of rivers that fishes cannot ascend to, and so some fish species begin to disappear.
In addition, some dams destroy the beauty of the natural landscape in which it is placed.
If a dam is made incorrectly, it can break and flood cities located in the vicinity of its downstream portion.
In the case of a more ambitious project, its consequences can be more severe: by embedding entire valleys, the construction of a dam can cause a human upheaval, forcing entire populations to move, and have an ecological impact by changing the local ecosystem.

A reservoir of water is created when a dam is constructed. Water stored in dams flows to a turbine. The flow drives an alternator that converts mechanical energy into electrical energy. The power of the water turns the turbine. The power produced can be measured using the flow rate and the height of the fall.

By Paul Richard :)

Here is the map of the largest dams in France. We see that the dams are in the South. The question is why? The dams are constructed in the south because there are mountains so there are spaces for the creation of artificial lakes.

Dams prevent salmon from migrating to their place of birth, which is where they go to breed; salmons always breed in the same place. Therefore, if their passage to their birthplace is blocked by dams, they can become extinct as the reproduction of their species would be prevented.

By alexis :)

In the case of anadromous species like salmon, dams can block or slow the rise of broodstock to their breeding areas. This may have resulted in the decline or even extinction of some species of migrating fish, as has been observed in the Meuse and in most European rivers.
Fish downstream dispersion can in turn be confronted with the forced passage through turbines of hydropower. The fish may then be more or less seriously injured or even killed during their passage through the turbines.Whatever its use, a dam may be an important barrier to fish migration.

Atlantic salmon from the Loire basin is inscribed on the Red List of Threatened Species Conservatory of "The International Union of Nature " in a petition warning the global conservation organization (WWF) environment. She says "Remove the dam Poutès, on the Upper Allier, built in 1941 in the heart of the best breeding areas, would maximize the rescue program undertaken under the Plan Loire grandeur nature, knowing that the work can be replaced by other renewables. "This iconic and authentic fish have already disappeared for the Loire basin without an awareness and mobilization of numerous partners. In the 90s, its population was very low, only about 200 individuals each year. For 5 years, the numbers range between 500 and 1,000 individuals on average. The mythical fish whose history is intimately linked to the Loire and its tributaries has benefited from various programs for its survival and repopulation. From the start of the salmon restoration project on the basin of the Loire, with the implementation of the Upper Allier salmon initiated by the Ministry of Environment, it became apparent need to create a parallel legal structure capable give it a wider dimension and ensure its sustainability after the program of the Plan Loire and its extension beyond 2006.

Alexis Marchand

There are an estimated 74,993 dams in the United States, which equates to nearly one dam built for each day since the signing of the Declaration of Independence. These dams block 600,000 miles of what had once been free flowing rivers. That’s about 17 percent of all rivers in the nation. Dams now block almost every major river system in the west of the nation. Many of these dams have destroyed important spawning and rearing habitats of Chinook, Coho and other commercially important salmon that fish industries depend on. In some once productive river systems such as Sacramento Valley where salmon was abundant, less than 5% of the original habitat now remains available to the salmon species. In the Columbia River Basin, which was once the most productive salmon river system in the world, less than 70 miles of that once great river still remains free flowing.
Commercial salmon fishermen have been fighting a rearguard action against widespread dam building since at least the 1930's, when the construction of large dams began. Throughout the west, many boondoggle dam projects were either never built, or were substantially modified, to protect irreplaceable fish runs as a direct result of the outcry of fishermen. There would be no mitigation hatcheries, for instance, had it not been for salmon fishermen demanding them as compensation for lost habitat.

By Paul :)


The stakeholders (people affected) in this dilemma are fishermen. Bears are also suffering from the consequences of habitat loss in the vicinity of dams and reduced source of food due to decreasing salmon runs. For thousands and thousands of years, salmon has been a primary source of food for people native to areas surrounding salmon breeding areas. Even at present, people around the world have a need for the salmon that go through their nearby salmon runs.
Bears are also affected by loss of salmon as they hunt at salmon breeding areas and rely on salmon as a source of food. The decreasing salmon population is a problem in the long term as the continual decrease in their number could result in the extinction of the species.

Les parties prenantes (personnes affectées) dans ce dilemme sont les pêcheurs, les ours et habbitat qui sont dans le domaine de la migration des saumons en baisse. Le saumon a été la principale source de nourriture pour les indigènes pour des milliers et des milliers d'années.Même dans le temps présent, les gens autour du monde ont un besoin pour le saumon qui passent par là les montaisons de saumons à proximité.

En outre, les ours sont effectuées par la perte de saumon dans le fait qu'ils ont besoin de chasser le saumon quand ils arrivent sur les lieux de reproduction. Cela pourrait être un problème dans une conversation à long terme, en raison du fait qu'il y aura de moins en moins de saumon jusqu'à ce qu'un jour, ils vont tous disparaître.

Danny P.


The constant concern for water over millenniums can be seen in the form of remains of dams found all around the Mediterranean. People have been looking for ways to retain water and, in both Mesopotamia and in Egypt of the Pharaoh’s, archaeologists have identified the first structures built to hold the precious water that all humans need.

In ancient times, Hindus and Arabs built tanks with small dikes several feet high using earth or boulders.

The ruins of what appears to be the oldest dam in the world were discovered in Egypt in 1885 at Kafara, which is 30km south of Cairo. It was a dam 12m high, built with rockfill around 5000 years ago. It was destroyed by a flood in the middle of the 3rd millennium BC.

Another achievement was made in late 4th millennium BC; a light-weight dam was constructed near Jawa in Jordan.

More recent but ancient achievements in dam construction include:

Dam Rusa 1 (734-714 BC) near Van in eastern Turkey,
Dam Sennacherib (705-681 BC) north-east of Nineveh,
1st dam Darius (521-486 BC) on the Iranian Fars in Kor.

Around the year 25 BC, Vitruvius described various hydraulic structures, but not dams. A century later, Frontinus mentioned the "lacus, which is super Villam Neronianam Sublacensem". This was moved to the area of water intake of the aqueduct Anio Novus because of the greater cleanliness of water. One and two smaller structures at the upstream and downstream parts were built during the time of Emperor Nero (54-68) to create artificial lakes at his villa in Subiaco, 50 miles east of Rome.

In Syria, the construction of dam Harbaqua, a dam that was 21m in height and 365m in length, was achieved by the Romans. Harbaqua was located between Damascus and Palmyra, and it was constructed under Emperor Hadrian (117-138) to fertilize the desert.

Cross sections of typical Roman dams

In Spain, the earth dams of Proserpina and Cornalvo that were constructed ahead of two aqueducts 12km and 25km long fed the city of Merida in the southwest. They could have been built during the reign of Trajan (98-117) who, as emperor of provincial origin may have contributed to this region.
Proserpina aqueduct had a maximum height of 12m and a length of 427m, while Cornalvo had a maximum height of 15m and a length of 194m. The Roman arch dam of Esparragalejo was built in the first century AD for irrigation. Finally the earth dam Alcantarilla, which was 14m in height and 550m in length, was the starting point of the aqueduct of Toledo, which stretched 38km. This dam was built in the second century AD.

In North Africa, dams were particularly numerous in Roman Tripolitania around Leptis Magna, which was the birthplace of Septimus - Severus (193-211). The largest gravity dam built by the Romans in Tunisia was located on the river near Kasserine Derb. These dams in North Africa did not just serve to provide water, but were also used for retention and formation of alluvial surfaces of arable land in the Wadi beds.

In Gaul, Roman engineers realized abutments against the sides of a valley to create a dam, which would provide water supply in Vallon de Baume, south of Saint-Remy de Provence (Glanum). They used a dam structure that had a sharp horizontal curve similar to those used in Turkey. This was the first application of dam engineering. The principle of the arch as used in this case had been long used by the Romans with great skill in buildng bridges, retaining structures and buildings. The site of Vallon de Baume was almost completely covered in 1891 by a new dam that was constructed.

As mentioned above, the Romans had long used the principle of the arch to stabilize their bridges, retaining structures and buildings. Ci-cons to the left of the cell wall were used as semi-circular support for the land of Butte St Antoine in Frejus. The others to the right supported the Gauls on the western outskirts of Frejus.

The oldest French dam seems to be on Pont Neuf Gouessant (Côtes d'Armor): This is an earth dam, which is 10m in height. It was built in the 13th century. However, the dam of St. Ironwood was the first major dam on French soil; built in 1680 to supply the Canal du Midi, it is 36m in height.
The first large French masonry dam seems to be that of Lampy (Aude) built in 1780, also for the supply of the Canal du Midi.

It is from this date, more exactly after the turmoil of the Revolution and the Empire (circa 1830 when industrial era began) that dams were constructed with an appearance with which we are familiar today rather than being constructed the empirical way. The first of these dams was the Furens dam, which was built between 1861 and 1866, 9km upstream from St Etienne. This dam can be considered the prototype of the modern dam that has a triangular profile. Although the Furens dam was constructed between 1861 and 1866, it was not until 1938 with the rise of the “white coal” industry that this modern design was used readily in France and around the world.


Since The Middle Ages, salmon has become scarce in some streams and has disappeared completely from many of them.

Allier River has maintained a population of salmon due to ongoing efforts made to keep the salmon population alive. Salmon, migratory fish par excellence are born in spring. The fry spend their first weeks in rollers at the heart of reeds. At the end of summer, it becomes a parr and feeds on aquatic invertebrates. After a year or two, it becomes a smolt in the springtime and begins its migration to the sea with the help of forces of floods and water flow. After a journey of 5000km in the Atlantic Ocean, it arrives and grows in areas off Greenland and the Faroe Islands. Once it becomes an adult and is sufficient in size, the salmon returns to the river where it was born to spawn.

This remarkable life cycle has been significantly hampered since the late nineteenth century by the increasing human activity and the creation of new infrastructure on rivers that were once salmonid paradise. These obstacles have taken different aspects related to either fishing or to the development of heavy rivers (dams, navigation …), or mechanical pollution (gravel extraction …) and chemical pollution (agricultural, industrial, household …).

Poaching, since the Revolution of 1789, had the first negative impact on rivers and caused the depopulation of broodstock particularly during the spawning period. In parallel to this, the bulk removal of parr in small mesh nets or rows has dangerously reduced the renewal of the species: in the late 1940s, for example, between Alleyras and Pont-du-Chateau, it is estimated about 80 kilograms of parr were destroyed daily. From 1973 to 1980, intensive fishing at sea has also seen a reduction in salmon numbers. In salmon farming areas, as recently discovered in Greenland, broodstock has been threatened by excessive fishing. Angling has also contributed to the reduction and to the possible extinction of the species albeit in much smaller proportions.

By 1972, professional fishing and the use of nets more than 5 meters wide on the Loire was denounced by the Association of Salmon Protection. .

The construction of dams for electricity production and the creation of water reservoirs for irrigation has progressively and permanently sterilized many spawning areas and has caused the disappearance of salmon on most rivers.

Alexis Marchand


The possible solutions for this problem are either to improve the course of salmon runs so that salmon can reach their breeding grounds more easily or to just demolish dams entirely. A solution must be found for this very serious problem.

The best solution that I can think of is just to demolish all dams, which would allow fish to swim freely to their breeding areas as they were able to back in the days before dams existed. I think that societies nowadays take everything for granted including fishes that are available to us but are in significant danger. At present, societies rely heavily on electricity and, as a result, species and their habitats are being destroyed.

Les solutions possibles à ce problème sont soit, mieux montaisons de saumon que les poissons puissent passer plus facilement. Or, il suffit d'effacer les barrages en deffinently. Nous avons besoin de trouver une solution à ce problème très néfastes sur nos mains.

La meilleure solution i peux penser à est simplement de supprimer tous les barrages et de laisser les poissons en liberté comme ils le faisaient retour dans la journée. Je pense que la société prend maintenant des jours les choses pour acquises, l'une étant le poisson qui sont à notre disposition mais sont sensiblement lésés par le fait que les jours de la société d'aujourd'hui relys sur l'électricité qui est de toute évidence être prises sur le habbitats environnantes.