MulkearLIFE – delivering catchment-scale river restoration
14 January 2015
Author: Ruairí Ó Conchúir, project manager, MulkearLIFE MulkearLIFE is a five year, partnership-based project working on the restoration of the Mulkear River catchment, which forms part of the Lower Shannon Special Area of Conservation (SAC). It is one of the most important integrated catchment management projects in Ireland and a flagship EU co-funded LIFE Nature project with a €1.75 million budget. Inland Fisheries Ireland is the lead partner, working with the Office of Public Works (OPW) and Limerick City and County Council, with additional funding from the National Parks and Wildlife Service. The main objective is to restore, through in-stream rehabilitation works, degraded habitats along stretches of the Mulkear River and its main tributaries – the Newport, Bilboa, Dead, Clare-Annagh and Killeengarriff rivers. While the key target species are Atlantic salmon, sea lamprey and otter, the project actions benefit a wide range of other fish species, invertebrates, birds and mammals by creating habitat complexity, thereby greatly enhancing the overall biodiversity of the region.
Degradation and loss of instream habitat, due to river drainage works dating back to 1874, has had a negative impact on the project’s target species. Drainage schemes, both recent and historic, have prevented rivers from recovering to a more natural state. Consequently, MulkearLIFE has implemented various habitat rehabilitation techniques to mimic natural conditions and create habitat complexity. Techniques including the installation of rubble mats, random boulders, paired deflectors and vortex stone weirs all help to break-up uniform habitat. Rubble mats, for example, are a useful feature when introduced to rivers that have been subject to past drainage work. They essentially mimic natural riffle areas, which were present pre-drainage. The construction of a rubble mat on the river bed reduces the cross-sectional area of the river, thereby increasing flow velocities at low summer flows. On the Mulkear River, individual mats have utilised up to 250 tonne of rock per mat, using rock which is generally 15 to 25cm in diameter and creating an interlocking top cobble layer. This results in important ecological changes on this top layer. The faster-flowing area on top of the rubble bed is quickly colonised by aquatic vegetation. In addition, a considerable variety of invertebrates favour such conditions and will colonise the rubble mat in significant numbers. This level of colonisation happens very rapidly (within months). More importantly, the fast-flowing nature of the water over the rubble mat provides exceptional habitat for young salmon and trout and, with invertebrate colonisation having taken place, provides such fish with ample food supplies.
Rubble mats to encourage biodiversity
MulkearLIFE has installed 28 rubble mats on 10km of the Mulkear River, utilising over 5,000 tonne of rock, helping to enhance habitat for salmonids and lamprey species, improving instream and riparian biodiversity. It has also enhanced over 15km of river channel through instream measures (random boulders, vortex and stone weirs) on the Clare-Annagh, Killeengarriff, Bilboa and Newport rivers using over 1,500 tonne of rock, with individual random boulders weight between one and three tonnes. To improve the distribution of sea lamprey in the catchment, MulkearLIFE addressed barriers to upstream migration. The population in the Mulkear is of national importance, but a number of old mill weirs have prevented sea lamprey from fully utilising the catchment. Passage has been monitored by MulkearLIFE through tagging and radio tracking to determine how sea lamprey navigate obstacles, what habitat they use and their preferred spawning zones. In 2011, MulkearLIFE designed, manufactured and successfully installed fish passes to assist sea lamprey ascend the major barriers at Annacotty and Ballyclogh weirs on the Lower Mulkear River, which greatly facilitated passage. From 2011 to 2014, over 93% of passage at Annacotty weir was achieved on MulkearLIFE’s two new sea lamprey tiles.
In August 2013, following 15 months of planning and consultation, MulkearLIFE removed a significant section of Ballyclogh weir which was a barrier to salmonid and sea lamprey passage. The reconfigured weir now allows unhindered passage to the rest of the catchment, where an additional 184km of river channel has been opened. The success of this work was particularly noted in 2014, where the total number of sea lamprey redds recorded in walkover surveys increased from 55 in 2012 to 85 in 2013 and then to an amazing 296 redds recorded in 2014. The Mulkear catchment has a good population of otter. In certain areas where otter numbers are low, the project is improving breeding and resting habitats. Otter survey work is a critical element of this work. MulkearLIFE has conducted five annual catchment wide otter surveys and one major six-month natal otter holt survey. Based on the findings of these surveys, ten artificial otter holts have been installed at various sites where they were considered necessary, several of which have been utilised. The project has improved otter habitat through extensive tree planting, enhancing river connectivity with a focus on old ox-bows, and has begun to address the degradation of riparian habitat in past historical drainage programmes. The Mulkear catchment has a number of non-native invasive plant species that impact negatively on the catchment. The riparian zone is the interface between the land and the watercourse. It is important as a food source and for the provision of cover for young salmon. Native vegetation improves bank function by protecting banks from erosion during flood conditions while invasive weeds lead to riverbank instability, erosion and siltation of gravel beds used by salmon for spawning. Large invasive plants, such as giant hogweed, Japanese knotweed and Himalayan balsam, reduce biodiversity by out-shading native plant species.
Problems with invasive species
Over the past four years, MulkearLIFE and its project partners, the OPW and Limerick County Council, have treated in excess of 200km of river channel for non-native invasives, including repeat and multiple treatments for the densest infestation of non-native invasive plant species. In addition, the project has established the Mulkear Conservation Volunteers (MCV) to undertake practical, river based, conservation activities. Over the past four years, the MCV has undertaken 48 outings (amounting to over 1,120 unit days) to improve river biodiversity. This has included tree planting, river clean-ups and the manual removal of Himalayan balsam and other non-native invasives from various ‘high nature value’ sites throughout the catchment. MulkearLIFE is also working closely with the local farming community to address local water-quality concerns and developing alternative solutions to cattle drinks for cattle with direct access to the river. It has established 12 ‘pilot learning sites’ on farms with extensive river frontage which act as ‘demonstration sites’ for other farmers and farm planners. One of the most enjoyable and rewarding aspects of the project’s work relates to the comprehensive Environmental Educational Programme (EEP) in local schools and within the wider community. A total of 74 schools (primary and post primary) have been completed as part of the EEP. This has involved half-day classroom engagements and separate half-day river based field trips with over 1,750 schoolchildren. Additionally, MulkearLIFE has conducted field-trips and training workshops for over 360 children and adults. This outreach work in local schools and within the local community is something about which the project is immensely proud. Hundreds of young adults and children now have an enhanced understanding of riparian habitat and the connectivity of rivers and wildlife corridors. The students also have a better understanding of Ireland’s fish species, invertebrates and water quality, the major threat of non-native invasive plant species and an appreciation of the seven principles of Leave No Trace. These seven principles (Plan Ahead and Prepare, Be Considerate of Others, Respect Wildlife and Farm Animals, Keep to Durable Ground, Leave What You Find, Dispose of Waste Properly and Minimise the Effects of Fire) provide an excellent grounding for all to enjoy rivers and the wider natural environment in an responsible way. Mulkear-LIFE is confident that these young people will be the future guardians of the Mulkear catchment and the Lower Shannon SAC. MulkearLIFE’s work came to an end on 31 December 2014. From now on, a five-year After-LIFE conservation plan will continue with elements of the project’s work in the catchment.http://www.engineersjournal.ie/2015/01/14/mulkearlife-catchment-river-restoration/http://www.engineersjournal.ie/wp-content/uploads/2015/01/New-Picture.bmphttp://www.engineersjournal.ie/wp-content/uploads/2015/01/New-Picture.bmpCivilLimerick City & County Council,OPW,water