2 Hydraulic Engineering for Nature - 2.3 Ecological Continuity

Question 1

Ecological Continuity Background

See diagram on slide 36

Answer 1

 Migratory fish species need to migrate between the headwaters of freshwater bodies and the sea for the purpose of reproduction.

 Transverse structures, such as pipes and conducts, weirs or barrages may seriously interfere with or completely obstruct migration in a water body.

Question 2

How to Improve Ecological Continuity

Answer 2

 Structure on or around artificial barriers (such as dams and locks) to facilitate fishes’ natural migration.

 Most fish passes enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps.

 The velocity of water falling over the steps has to be fast enough to attract the fish to the ladder, but it cannot be so fast that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver.

Question 3

Fish Passes (Fish Ways, Fish Ladders, Fish Steps)

Answer 3

See picture on slide 38

Question 4

Rock Ramp

See picture on slide 39

Answer 4

 Mimics natural structures

 Replaces or complements smaller artificial structures

Question 5

Bypass River

Answer 5

See picture on slide 40

Question 6

Pool and Weir Fish Pass

See picture on slide 41

Answer 6

 Series of small dams and pools create a long, sloping channel

 Fish swim from box to box, upstream they have to jump

Question 7

Vertical Slot Fish Pass

See picture on slide 42

Answer 7

 Slots allow fish to swim upstream without leaping.

 Handling of seasonal fluctuations in water levels

Question 8

Baffle Fish Pass

See picture on slide 43

Answer 8

 Symmetrical close-spaced baffles (plates) in a channel

 Reduces velocity, no resting place necessary

 Easy moving

Question 9

Fish Lock (Sluice)

Answer 9

See pict on slide 44

Question 10

Fish Elevator

See pict on slide 45

Answer 10

 Carries fish over high barriers

 When enough fish accumulate in a collection area, they are nudged into a hopper that carries them around the barrier.