Facilitating the passage to fish

1993/05/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Teknologia
• Arrantza

Each year, salmon and sea trout begin migration to North Wales to spawn and cross Conwy Falls 12 m high along the way. From this summer there will be an inclined tunnel to reach the top of the falls.

Giving way to fish is not a new idea. It is relatively normal for fish to overcome reservoirs by building slopes in reservoirs.

The first idea that occurred to the company that monitors Conwy Falls was the construction of a tunnel. To prevent fish from being exhausted, 45 cm wells would be built. Therefore, a total of 28 wells. But to make so much well it was necessary to build a very long tunnel, with a cost of 60,000,000 pesetas. or that, being more than 3,000,000 pounds, it was impossible to develop the project as it was.

Then civil engineer David Donaldson found a simpler solution. Building a total of 14 wells and obtaining two different water levels in each well (see figure), the length of the tunnel would be half the previous project, i.e. 48 m. The water is therefore poured in zigzag, with small jumps.

Thus, in addition to the length of the tunnel in half, the cost has been reduced, so the number of eggs laid in August this year will be 40% higher than last year.