Micro Hydropower and Fish. Garry O Neill. Senior Fisheries Officer. Inland Fisheries Branch.
1. Value of Fisheries. 2. Life cycle of the Salmon. 3. Potential impacts of Hydro s on Fish. 4. Fisheries Legislation. 5. Mitigatory Measures.
1. Fisheries are valuable and contribute to the rural economy Commercial fisheries in decline-salmon trout and eels. Recreational fishing Angling. There are over 4.0 million anglers in UK and 60.0 million in Europe. Recent report concludes that angling is worth 22M to the NI economy and supports up to 700 full or part time jobs. The presence of fish, particularly salmon indicates a clean green environment which is attractive to investors. 2. Fishing rights in freshwater are owned by individuals or groups of individuals. Fishing rights may or may not be attached to the surrounding land. 3. Legislation has developed to protect these assets and rights.
HOLDING Sea 1 to 2 yrs NURSERY 1 to 3 years GRAVEL Mar to Apr Nov to Jan May to Aug
Fish can be found in most rivers and streams so it should be assumed at the outset that fishery protection measures will be required.
Potential impacts of a Micro Hydro on fisheries. Entrapment of fish at intake and outlet points. Damage to fish passing through machinery. Dewatering a stretch of river affecting the ecology. Obstructing fish migration.
Map1. The Randalstown hydro site on the River Maine, Co. Antrim. N Turbine Intake # De-watered Stretch Turbine House # Turbine Outlet 0 100 200 300 400 Meters
River Intake Point (Sluice Control) Dam Diagram of a low head run of the river hydro Fish Pass Flood Control Sluice or mechanism Mill Intake Layde (Head Race) Outlet point Outlet Layde (Tail Race)
Fisheries Legislation. Ref: www.northernireland-legislation.hmso.gov.uk Fisheries Act (NI) 1966. Foyle Fisheries Act (NI) 1952. International Legislation e.g. European water framework directive; Fish Directive.
Fisheries Act (NI) 1966 Section 54 requires the provision of a fish pass in any dam constructed across a river. Section 58 requires the closure of sluices during the weekend period or when the mill is not working. Section 59 requires the operator to provide and maintain gratings to prevent fish entering the mill.
Provision of a fish pass. (section 54) Design will depend on the shape and height of the weir. Design must be approved by this Department. Fish pass should : Be placed on the face of the weir so that fish are able to find the entrance. Be fully supplied with water at all times. Not be drowned out during flood conditions. Operate without the need for manual control. Sited or secured to prevent poaching. Velocity of water in the pass should not exceed the swimming ability of the fish. Pools should be sufficiently large to prevent fish becoming disoriented and the side walls of sufficient height to prevent fish jumping out (Salmon and Trout). Should allow the passage of eels and lampreys. Economical to construct.
Notch Examples of fish pass. 1. Overspill and notch. Effective for salmon and trout. Suitable for low head weirs up to 1.5m above river bed. Depth of pool should be 1.5 times the height of the weir Downstream Pool Weir crest Maximum 1.5m above bed level Maximum 1m Upstream water level Weir notch Pool
The type of fish pass shown has proved effective under a range of flow conditions for weirs with a crest level up to 1.5m above riverbed. 2 To mill Pool
Example of fish pass. Weir crest 2. Diagonal baulk and notch. Diagonal Baulk directs f low Notch cut in weir face provides a flow of water attractive to fish. Diagonal baulk concentrates the flow into a pool downstream. Fish movement Pool Upstream water level Effective on weirs with gently sloping face. Notch Diagonal Baulk Weir face 30 or less
Example of fish pass. 3.Pool and Traverse fish pass. 0.6m 0.5m 2m 3m Consists of a series of walls and pools which allow fish to move over the weir. Low velocity of water through pools Fish are able to travel considerably long distances. Useful on weirs with a high head.
5 Fish pass on the Carey river, Ballycastle. The series of pools allows fish to ascend quite high obstaclesabout 4metres in this case.
Provision of gratings. (section 59) Operator is required to provide and maintain gratings at the points where the water is diverted from and returned to the river. Dimensions are specific. 25mm between bars on the inlet. Gratings must cover the entire watercourse to the height of the highest flood. Gratings on the inlet must be covered with a wire lattice during certain periods to prevent the ingress of small fish.
Problems with gratings. Difficult to maintain. Often remote from the site. Tend to block and reduce water flow. Fish may become trapped. Department may issue an exemption permit where it is satisfied that acceptable alternative measures can be provided. Such permits will only be issued after consultation with directly adjacent fishery interests.
Grating placed on the inlet to a small hydro.
Diagram 10 Example of a self cleaning screen currently in operation at Ballinderry Fish Hatchery. weir Fish a nd debris river Perforated screen To hatchery 8 Water flows through the screen and is diverted to the hatchery via a pipe Fish and debris
Example of self cleaning screen being installed at a turbine near Cookstown 13
River Dam Fish movement To mill Fish can become entrapped at this point when there is little water flow over the dam Grating at right angle to flow Head race Gratings placed at inlet, at right angles to the flow conform to fisheries law but may cause fish to become trapped.
River Dam Fish bypa ss adjacent to grating allows free passage over dam crest Fish move ment Grating set parallel to flow To mil l Debris deflecting boo m Head race It is more effective to place the grating on the inlet parallel to river flow. This will divert fish away from the grating. Fish bypass should be provided. Debris deflecting boom helps to keep the grating clean.
Example of a fish by- pass structure for which an exemption certificate may be granted. Enables better protection for fish. River X Y X Fish Bypass Y Fish movement Maximum angle 30 Ve rti cal fish screen Detail: see diagram 4b Grating easier to clean. To mill More secure site. May be fitted with self cleaning device.
Details of fish bypass arrangements Adequate supply of water. Well maintained angled fish screen. Rounded surfaces. Shading and security. Good access back to river. X Smooth rounded surfaces Y Angled f ish screen Fish Bypass To river Shading Water level Fish movement Water flow Note : Shading over the fish bypass encourages fish to enter and protects from predators. Walls of pool to be high (1m above water level) - to prevent fish jumping out* Pool Pool 1m 2m 0.5m : maximum drop X Water Level : Intake layde Series of pools to return to the river. * Smooth bore pipe is equally effective in low head situations (<3m) Y
Grating set on outlet at right angles to flow. Upstream migrating fish will be attracted to the flow from the turbine and become vulnerable to predation. River Fish Movement Outlet layde Grating set a right angle to flow. Fish are attracted to this point and are vulnerable to predation and / or poaching
GRATING SET ON OUTLET PARALLEL TO BANK River Encourages fish to move upstream Fish less vulnerable to predation Outlet layde Fish Movement Grating set parallel to bank encourages fish to move upstream
Example of gratings set parallel to the water flow. These give much better protection to fish and are easier to keep clean. River Abstracted water 16
Control of water abstraction. (section 58) Fisheries Act requires that Hydro must not operate for a period of 24 hours each weekend. This provision is arbitrary and does not satisfy: The natural ecology of the river. Angling in the stretch. Upstream and downstream fish migration. Abstraction is now largely controlled by abstraction licences however, the Department may control abstraction through the issue of an exemption under the fisheries Act
River Bush: Flow (cumecs per metre river width) and upstream salmon movements. 180 160 140 120 No. Salmon 100 80 0.08 1.1 60 40 20 0 0.00 0.50 1.00 1.50 2.00 2.50 3.00 Cum ecs per metre river w idth
Examples of an exemption under section 58. Exemption from weekend closure may be considered if operator; 1. Maintains adequate flow in the dewatered stretch to permit upstream migration for salmon during the period of peak migration. (July to October). 2. Closes the hydro during period of smolt migration (April and May).
Summary. Fish protection measures must be included by law at all points where water is abstracted from a watercourse containing fish. These include screens, fish passes and limits on abstraction. Advice on suitable measures should be sought from fisheries technical staff in DCAL. With good management and common sense on the part of the abstractor, well maintained, fish protection measures at abstraction points can minimise damage to fish stocks.
SW N SE Area Fishery Offices: Northern Area: Garry O Neill. River Bush Salmon Station. 21 Church Street, Bushmills, Co. Antrim. BT57 8QJ. Tel: 02820731435. garry.o neill@dcalni.gov.uk South Eastern Area: Peter Lynch. Fisheries Office, Castlewellan Forest Park, Castlewellan, Co. Down BT31 9BU. Tel: 02843778937. peter.lynch@dcalni.gov.uk Fishery Office Boundaries. South Western Area. John Kane. Fishery Office. Enniskeen House, Killyhevlin Enniskillen, Co. Fermanagh. BT74 4EJ. john.kane @dcalni.gov.uk