WO2007011274A1

WO2007011274A1 - Device for migratory fish

Info

Publication number: WO2007011274A1
Application number: PCT/SE2005/001176
Authority: WO
Inventors: Jan-Erik Almqvist
Original assignee: Vagverket
Current assignee: Vagverket
Priority date: 2005-07-22
Filing date: 2005-07-22
Publication date: 2007-01-25
Anticipated expiration: 2008-01-22

Abstract

The invention relates to a device for fish migration from a low-lying point, for instance a watercourse (2), to a high-lying point, for instance a road culvert (3). The device provides a closed waterway between the lower point (2) and the upper point (3), with an inlet (12) at the upper point and an outlet (11) at the lower point (2). The water flow in the device has its maximum velocity at the outlet (11) or the inlet (12) and is adjusted to allow fish (4) to enter, that is the cross-sectional area of the outlet (11) is adjusted so that the water flow through the outlet is not greater than to allow the fish to enter. The device comprises a container (10) having an outlet (11) and being arranged at the lower point (2), and a pipe (13) arranged between the container (10) and a connection part (14) connecting to the upper point (3).

Description

DEVICE FOR MIGRATORY FISH

The invention relates to a device for fish migration from a low-lying point, for instance a watercourse, to a high-lying point, for instance a road culvert.

When building motor roads, railways and the like, it is common to arrange a bank as a stable base for the road. If a watercourse is to be crossed, a bridge is built over the watercourse or the water is conducted through a road culvert under the road. The road culvert is dimensioned so that also a great spring flood can pass without causing flooding or damaging the road. Fish migrating upstream in a watercourse to spawn, however, sometimes experience problems in the road culvert. The most frequent problem is that there is a difference of height between the watercourse and the road culvert that the fish do not manage. Even a difference of height which the fish would normally manage may be enough since the velocity of the water increases through road culverts, thus making it impossible for the fish to continue.

A prior solution to this problem is to install a fish ladder. The fish ladder consists of a number of small dams with a small difference of height so that the fish can swim/ jump from dam to dam, see for instance US 2003/0133754. The drawback of this solution is that the fish ladder will be relatively long and require a large surface around the watercourse, which is not always available. Moreover a fish ladder is expensive to install. Other known solutions involve the use of some kind of system of locks where the flow is controlled by gates which are closed and opened for the fish. However, such systems require power supply and regular surveillance to work in a satisfactory manner.

The invention solves the above problem by a device for fish migration according to the independent claim.

Fig. 1 shows the invention arranged for a road culvert. Fig. 2 shows the invention seen from downstream. Fig. 3 is a front view of the pipe and the connection part.

Fig. 1 shows a device for fish migration according to the invention. The device (1) helps the.fish (4) to bridge a difference in altitude (N) between a lower point, for instance a watercourse (2) where the fish are positioned, and an upper point, for instance a road culvert (3). The device creates a waterway between the lower point, the watercourse (2), and the upper point, the road culvert (3). The waterway through the device (1) is in use filled with water. The device comprises an inlet (12) for the water flow at the upper point and an outlet (11) at the lower point (2). The velocity of the water flow in the device varies, inter alia depending on the area of the cross- section where the water passes. The device is adjusted so that the velocity of the water flow is at its maximum over a short distance.

Fish swimming upstream manage a relatively high flow velocity as long as a short distance is involved. Over long distances, the fish manage a considerably lower velocity. The invention concerns a device with a waterway that utilises this fact. By letting a short distance of the waterway through the device have a smaller cross- sectional area than the rest of the device, the flow velocity will be at its maximum over this short distance. The cross-sectional area and the length of the distance are adjusted to allow the fish swimming in the watercourse to manage swimming through.

An embodiment of the invention is to let the highest velocity occur at the outlet, which is the point where the fish enter the device. The outlet is made to correspond to a short distance and the cross-sectional area is adjusted so that the fish manage the higher velocity. Once the fish have left through the outlet, the cross-sectional area is increased and the velocity of the water flow is reduced. Conveniently the cross-sectional area increases to a relatively great extent so that the flow velocity decreases to a great extent and the fish thus can rest. Since the outlet has the smallest cross-sectional area in the device where the water passes, the velocity of the water flow is at its maximum and then proportional to the cross-sectional area of the outlet. The velocity of the water flow also depends on the height of fall between the upper and the lower point.

An alternative embodiment involves letting the inlet having the smallest cross- sectional area. It is also possible to let the smallest cross-sectional area be in other places in the device, but it is suitable for the fish to be relatively rested before swimming through the narrower section and then also have the possibility of resting afterwards. The device comprises a container (10) arranged in the watercourse (2). The container (10) has an outlet (11) where the fish enter. The outlet is arranged under the water level in the watercourse (2). The container is also connected to a pipe (13) arranged between the container (10) and a connection part (14) connecting to the road culvert (3).

The connection part (14) has a collar (15) which is slipped onto the pipe (13) and a connection device (16) for the road culvert (3), thus allowing the connection part (14) to be detachable. In the autumn after the fish migration is over, the connection part is removed and water can flow freely through the road culvert in the next spring flood. After the spring flood, the connection part is mounted again in time for the start of the fish migration season.

The connection part (14) comprises the inlet (12) and parts (18, 19) which dam up the water in the road culvert (3). The inlet (12) suitably has an area corresponding to the area of the pipe. The parts (18, 19) ensure that the inlet is covered with water and, thus, the device is filled with water. If the water flow should be so great that the water does not manage to flow into the inlet (12), the excess water flows over the edge (20) and continues outside the device down to the watercourse (2).

The device (1) works in such a manner that the fish (4) enter the container (10) through the outlet (11). When the fish have swum through the container (10), the fish start upstream through the pipe (13). The inclination and diameter of the pipe and the outlet (11) are adjusted so that the water flow is not greater than to allow the fish to swim through. Different species of fish manage water flowing at different velocities, and therefore the device is suitably adjusted to the species which migrates/migrate in the watercourse. A suitable diameter of the pipe is in most cases between 20 and 40 cm, which with a suitable inclination of the pipe results in a flow velocity of 1-2 m/s.

The container (10) also has a lid (17) to facilitate cleaning of the container. The container (10) and the pipe are suitably arranged permanently in the watercourse, and only the connection part (14) is mounted and dismounted. However, in small watercourses or with temporary differences in altitude, the entire device (1) can be mobile. A device according to the invention could be dimensioned, for instance, for a maximum flow velocity of 4 m/s, a velocity that many migrating fish manage over a short distance. With a difference in altitude of about 70 cm, and a pipe with a diameter of 30 cm, the outlet should suitably be a hole with a diameter of about 15 cm for the velocity to be 4 m/s.

The invention concerns a device which because of its design allows the fish to migrate upstream, without any movable parts and control systems being necessary. To this end, the invention comprises a waterway which has a varying cross-sectional area. In this manner, the flow velocity through the device will be different depending on the cross-sectional area. The device is preferably dimensioned so that the cross- sectional area is at its minimum in the outlet. The flow velocity through the device will thus be at its maximum in the outlet. The high flow velocity occurs, however, only over a short distance before the fish enter a part having a greater cross-sectional area and, thus, a lower flow velocity and allowing the fish to rest.

The device can also be supplemented with a lid at the outlet (11). This, in combination with the cross-sectional area of the outlet (12) being made smaller than the outlet (11), results in the velocity of the water flow being at its maximum in the inlet (12). The fish have no difficulties in entering the outlet (11) where a sensor detects the fish and closes the lid and prevents water from leaving the container. The water flow through the inlet (12) continues and fills the entire device with water so that the fish can swim upstream to the road culvert. When the fish have left the inlet (12), a sensor detects this and opens the lid at the outlet (11). This solution allows the fish to manage relatively great differences in altitude.

In case of great differences in altitude, it may be necessary to arrange one or more dams between two or more devices according to the invention. The device makes it possible, in an inexpensive and space-saving manner, without requiring electricity, for migrating fish to manage differences in altitude. This is due to the fact that the device creates a water-filled way with a flow velocity between the altitudes, which is possible for the fish to manage. The device is shown between a watercourse and a road culvert, but it can also be used between other types of differences in altitude, such as embankments, power stations, reservoirs and temporary obstacles on building sites.

Claims

1. A device for fish migration from a low-lying point, for instance a watercourse (2), to a high-lying point, for instance a road culvert (3), with an inlet (12) at the upper point and an outlet (11) at the lower point (2), characterised in that the device has a varying cross-sectional area to provide a varying flow velocity in different parts of the device.

2. A device as claimed in claim 1, characterised in that the part of the device with the smallest cross-sectional area is short so that the fish manage the higher flow velocity.

3. A device as claimed in claim 1 or 2, characterised in that the cross-sectional area of the device is smaller at the outlet (11) than in the other parts of the device.

4. A device as claimed in claim 3, characterised in that the cross-sectional area of the outlet (11) is adjusted so that the water flow through the outlet is not greater than to allow fish (4) to enter.

5. A device as claimed in any one of preceding claims, characterised in that it comprises a container (10) having an outlet (11) and being arranged at the lower point (2), and a pipe (13) arranged between the container (10) and a connection part (14) connecting to the upper point (3).

6. A device as claimed in claim 5, characterised in that the container (10) comprises a lid (17) to facilitate cleaning.

7. A device as claimed in claim 5 or 6, characterised in that the connection part (14) is detachable.

8. A device as claimed in any one of claims 5-7, characterised in that the connection part (14) comprises the inlet (12) and parts (18, 19) which dam up water so that the inlet (12) is covered with water.

9. A device as claimed in any one of the preceding claims, characterised in that the velocity of the water flow in the pipe (13) is adjusted so that the fish (4) manage to swim along the entire length of the pipe.

10. A device as claimed in any one of the preceding claims, characterised in that the cross-sectional area of the container (10) is great to provide a low velocity of the water flow.