The second fish passage solution for discharge sill on Dâmboviţa river.

1. Engineering techniques developed to achieve longitudinal connectivity
on the rivers. Case study developed on the DâmboviŃa River
Dr.eng.Răzvan Voicu
rzvnvoicu@yahoo.com , getiiliberi@gmail.com
In Bucharest, the DâmboviŃa River is completely hydrotechnically arranged
(lakes, dams, discharge sills, concrete bed etc.). There are different species of fish (chub,
burbot, wild carp, common nase, common rudd and so on) in the DâmboviŃa River. The
migration of these species is blocked by the presence of some hydro-building activities
on the river. All such construction shall be equipped with systems for fish migration
according to the Water Framework Directive (60/2000/CE). To achieve a system for
ichthyofauna migration on the DâmboviŃa River upstream – downstream the discharge
sill near Auto Vitan Market, I suggest the following solutions:
SOLUTION I
A metal or concrete pillar is installed at the pile 1, three meters away from the
first concrete plate 2, approximately. A metal plate is welded on the metal pillar. Then a
telescopic hydraulic cylinder is welded on the metal plate (Fig. 1 – telescopic hydraulic
cylinder, pile 1, concrete plate 2, metal or concrete pillar, Positioning the metal or
concrete pillar).
pile 1
telescopic hydraulic cylinder
watercourse
concrete plate 1
metal or concrete pillar
concrete plate 2

2. Figure 1 Positioning the metal or concrete pillar
A metal bar, cogged on the inside, is fixed to the right bank of the watercourse,
which is covered by concrete (as the entire watercourse is) vertically. An electric motor is
attached to this cogged bar (Fig. 2 – pinion, electric motor, cogged bar, Fixing the electric
motor to the cogged bar). The motor is driven by a pinion, following the rack nacelle
principle known and used worldwide (Fig. 3 – Rack nacelle a and b).
right bank pinion electric motor
watercourse
cogged bar
Figure 2 Fixing the electric motor to the cogged bar
a
rack nacelle (nacelle-italiastar.ro)

3. b
rack nacelle (nacelle-italiastar.ro)
Figure 3 a and b - Rack nacelles
A horizontal bar will be fixed to the cogged bar using two bearings. This bar is
also fixed to the electric engine and with the help of which it can move vertically and
inside the river as well. (Fig. 4 – metallic rectangular parallelepiped (1), metal bar with
variable geometry, Fixing the electric motor to the cogged rail). Vertical bar can move
vertically due to a hinge that locks the bar in the vertical plane. A rectangular
parallelepiped made of a metal grid that has no upper horizontal surface is welded to the
metal bar with variable geometry. (Fig. 5 –Fixing the metallic rectangular parallelepiped
(1) to the metal bar with variable geometry)).
bearings
metal bar cogged bar
pinion
electric motor
metal hinge
metal bar with variable geometry
Figure 4 Fixing the electric motor to the cogged rail

4. electric motor
right bank pinion metallic rectangular parallelepiped (1)
watercourse
cogged bar
Figure 5 Fixing the metallic rectangular parallelepiped (1) to the metal bar with
variable geometry
The four vertical surfaces of the metallic rectangular parallelepiped (1) are
equipped with folding systems made from the same material (metal grid). The folding
surfaces are fixed to some folding bars and they withdraw in line with the parallelepiped
surfaces. (Fig. 6 – folding bar, folding surface, electric motor for folding mobile surfaces,
metallic rectangular parallelepiped, Positioning the folding surfaces on the metallic
rectangular parallelepiped). These bars can be folded due to small motors attached
outside the metallic rectangular parallelepiped.

5. folding bar
folding surface
electric motor for folding mobile surfaces metallic rectangular parallelepiped (1)
Figure 6 Positioning the folding surfaces on the metallic rectangular
parallelepiped
Many migratory fish, regardless of species (for example) gather in the concrete
plate area 2 wanting to overcome the weirs with variable geometry. (Fig. 7 – Area of
study and Fig. 8 – weir with variable geometry). The difference in level between concrete
plate 1 and plate 2 is 1.5 m.

6. concrete plate 2
Figure 7 Area of study
Figure 8 Weir with variable geometry
After withdrawing, these folding surfaces pass about 30 cm over the water level
which allows catching fish fauna inside the metallic parallelepiped. In the case study, the
lower rectangular basin reaches a depth of over one meter. After the metallic
parallelepiped (1) reaches the maximum, due to the rod it is fixed to, the telescopic
hydraulic cylinder pushes the parallelepiped up to the angle where all the fish fauna
moves between the horizontal and one of the vertical surfaces of the parallelepiped. (Fig.
9 – Maximum level of the telescopic hydraulic cylinder). The lower left corner of the
metallic parallelepiped is higher than the other corners, resulting in a funnel within the
two surfaces, which directs the fish to the left corner, but at a lower level after folding.
(Fig. 10 – System of fish redirecting inside the metallic parallelepiped (1)). Fish gather
near the weirs in order to go upstream, but if there is a system for fish redirecting made of
electromagnetic field generators fixed to the left bank, then the fish will get near the
metallic parallelepiped. Thereby, fish can be blocked and pass downstream of the weir. A
fence made of metal grid can also be set as a system for fish redirecting.

7. metallic rectangular parallelepiped (1)
right bank electric motor
pinion
metal hinge
concrete plate 1 concrete plate 2
cogged bar telescopic hydraulic cylinder
Figure 9 Maximum level of the telescopic hydraulic cylinder
Figure 10 System of fish redirecting inside the metallic parallelepiped (1)
At the metallic parallelepiped base near the lower left corner, there is a circular
window to which a durable flexible plastic tube is attached. (Fig. 11 - The flexible tube,
Positioning the flexible tube in the metallic parallelepiped (1)). The flexible tube of about
40 cm diameter will be located above the maximum level of the weir and will be fixed to

8. the right bank using some metal cables allowing it to move vertically. (Fig. 12 – Fixing
tube system, metallic parallelepiped 2, Positioning the flexible tube towards the right
bank). Fixing the tube to the right bank and its flexibility allow its anchoring to the
metallic parallelepiped without affecting the discharge sill. For moving downstream –
upstream the same flexible tube, but using other parallelepiped made of metal grid, will
be used (Fig. 12).
metallic parallelepiped (1)
the flexible tube
Figure 11 Positioning the flexible tube in the metallic parallelepiped (1)

9. SOLUTION II
fixing tube system metallic parallelepiped (1)
the flexible tube right bank pile 1 pile 2
metallic parallelepiped (2)
Figure 12 Positioning the flexible tube towards the right bank
The rectangular parallelepiped 2 preserves the same characteristics regarding the
mounting of the flexible tube, redirecting the fish inside and transporting the fish
upstream of the discharge sill. The difference lies in the way of fixing the metallic
parallelepiped 2 to the metal housing of the electric motor . (Fig. 13 metal support,
folding bar, Mobile system supporting the metallic parallelepiped 2).

10. bearings
metal bar cogged bar
folding bar metal support
motor electric
metallic parallelepiped (2)
Figure 13 Mobile system supporting the metallic parallelepiped 2
The process of lifting the metallic parallelepiped 2 is performed on the same
principle: rack nacelle, but in this case there is no telescopic hydraulic cylinder to incline
the parallelepiped 2. The parallelepiped 2 will be inclined by using a folding bar for the
fish to reach the flexible tube (it rotates in the same plane) fixed inside the electric motor.
Because the water depth is about half a meter, the parallelepiped 2 is directly supported
by the concrete river bed. (Fig. 14 – the concrete river bed, metal support, stationary
metallic parallelepiped 2, folding bar). In this case the redirecting system consists of
some electromagnetic field generators located on the left bank.

11. right bank
metallic parallelepiped 2
cogged bar
the concrete river bed
metal support
folding bar
Figure 14 Stationary metallic parallelepiped 2
Electromagnetic field generators operate separately, both upstream and
downstream. When lifting the metallic parallelepiped 2 by the means of the rack nacelle
system, the upstream electromagnetic field generators stop for the fish fauna reaching
upstream the discharge sill to continue the migration and not to come back, by the means
of the upstream metallic parallelepiped (1), downstream of the spillway sill. This solution
is not complicated, is modern, does not require large financial resources, is space saving,
does not destroy the discharge sill components, and can operate entirely using solar
energy. All the components of the system are stainless steel or are made of other non-corrosive
materials. During winter, the system can be uninstalled and used for another
discharge sill having approximately the same dimensions. The presented dimensions of
the system are only trial, but accurate when needed. This system was introduced on a
concrete area to better understand the positioning and operation thereof. It can be applied
anywhere in the world.

12. All rights reserved
Bucharest
2013