Establishing a migration system for the ichthyofauna upstream-downstream of the weir located on the DâmboviŃa River in Bucharest

Ph.d eng.Răzvan Voicu

INTRODUCTION

Discontinuation of longitudinal connectivity of waterways in Romania and

preventing fish migration upstream towards the spawning areas as a result of barring

watercourses in order to produce electricity, flood defense and water supply has led, in

time, to a decrease number of migratory fish species present in the rivers of Romania.

Ecological and economic implications of this phenomenon have determined experts to

seek solutions for restoring longitudinal connectivity of waterways and providing fish

migration towards breeding habitats upstream of some dams.

An important element relating to good management of migratory fish species in

rivers, both at European and national level, is currently the arranging or removing

transversal obstacles that hinder fish migration. In this respect, the obligation to achieve environmental objectives under the Water Framework Directive (60/2000/CE) and the

directives thereunder entail the assurance solutions regarding the fish migration and also

the recovery of longitudinal connectivity of rivers.

Also, the national legislative framework regarding the water policy (Water Law

no. 107, with subsequent amendments, NT No. / 2006 OM 1163/2007), reflecting the

European directives, mentions the obligation to ensure construction works in order to

protect the fish migration and also to maintain the ecological balance in the reservoirs.

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).

As a case study, the DâmboviŃa River weir located on Independence Splai near

“Regie” University Campus (fig. 1) was chosen.

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Figure 1. Weir on the DâmboviŃa River, near “Regie” University Campus

As it can be seen in Fig. 1, the case study is a weir with mobile sluiceways. All

three sluiceways are the same size. In general, as it can be seen in Fig.1, two of the three

sluiceways, the middle one and the one near the left bank are open so that water can pass

over them. The sluiceway on the right is set up at maximum so that the water level is

blocked entirely (fig.2 a and b). The sluiceways are driven by cylinders fixed in the (dam)

weir foundation.

After performing a detailed study, I could observe that right at the sluiceway near

the right bank, where the water is completely blocked, fish gather in large numbers (fig.

2.b). At the other sluiceways, fish stop their migration at approximately 30 cm distance

from them, feeling the stream flow discharge.

sluiceway near the right bank central sluiceway

pile I pile II

sluiceway near the right bank

Figure 2( a and b). Sluiceways positioning

b)

a)

It is necessary to provide a window and a metal door into the sluiceway near the

right bank, on the water level (fig. 3 a and b).

pile I

the right bank

window

piston sluiceway

window

Figure 3 (a and b) Sluiceway window positioning-indicative scheme

a)

b) b)

This window is provided with a door driven by two telescopic hydraulic cylinders

fixed to the sluiceway obliquely (fig. 4 a and b). When the cylinders reach the maximum

level, the door rises above water level by 10 cm. The metal door is fixed to the cylinders

by means of springs helping it to perfectly fold on the sluiceway.

piston metal door

metal door

telescopic hydraulic cylinder

sluiceway

weir foundation

Figure 4 ( a and b). Metal door positioning on the sluiceway – indicative scheme

The water pressure on the metal door is almost insignificant, being positioned on

top of the sluiceway. A rectangular metal canal with the same size as the window has to

be fixed to the sluiceway inside by the means of some screws (fig. 5).

b)

a)

rectangular metal canal

metal door

sluiceway

telescopic hydraulic cylinder

weir foundation metal screws supporting pole

Figure 5. Rectangular metal canal positioning – indicative scheme

The metal pole is fixed to the dam foundation by the means of some screws. The

first rectangular pool of water catchment, which represents the refuge area for fish, is

fixed to the canal. The rectangular basin is made of galvanized steel sheet piling, is 50 cm

high and is attached to the pile I (fig. 6)

screw

first rectangular basin

pile I

supporting bar

Figure 6. The first rectangular basin positioning - indicative scheme

Another rectangular parallelepiped basin will be fixed to the rectangular basin

(fig. 7). The second rectangular basin is made of galvanized steel sheet piling, is 40 cm

high and is attached to the pile I and it will reduce the water speed coming through a

window of the first basin (fig. 8).

The Module M2, which almost reaches the left bank, will be fixed to the second

rectangular basin. (fig. 9).

right bank

first rectangular basin sluiceway

module M1

second rectangular basin

metal grille pile I

Figure 7. The second rectangular basin positioning - indicative scheme

pile I

sluiceway near the right bank

module M1

overflow window

acces window module M2

window basin II

window basin I

first rectangular basin second rectangular basin

Figure 8. Connections between the two rectangular basins - indicative scheme

second rectangular basin first rectangular basin

pile I

module M 2

pile II

Figure 9. Module M2 positioning - indicative scheme

The third module M3 is circular and makes the connection between the module

M2 and the left bank (Fig. 10 – the left bank, M4 module, M3 and M4 modules

positioning).

DâmboviŃa River

pile II

module M2

module M3

the left bank

module M4 metal grille

Figure 10. M3 and M4 modules positioning

For protecting the connection between them, the modules M2 and M3 are

provided with double reinforcement on the horizontal surface, and also a metal

supporting pole for preventing the buckling. Module M4 will be connected to the

DâmboviŃa River (fig. 10). The fish species will be protected by some metal grilles fixed

to the components of the system by using some metal hinges. All components of the fish

migration system are rustproof and removable. In the event that there will be no need for

of fish fauna migration, all the components of the system mentioned above can easily be

detached from the weir and some of them can be used for another weir as system for fish

migration. This method for fish fauna migration can be successfully applied anywhere in

the world.