Lough Gur, Limerick Ireland

Lough Gur is one of only two lakes greater than 0.5km2 in County Limerick.  The lake, which covers 76 hectares, is a shallow (maximum depth of 4.4 m, a mean depth of 1.59 m), hard-water, eutrophic lake, with continually high levels of phosphorus. There are no rivers flowing into the lake, which is fed mainly by groundwater springs and surface runoff from adjacent lands. Due to its enriched nutrient state, the lake suffers periodically from algal blooms with poor oxygenation conditions and elevated pH (>9). Not alone have the blooms been unsightly, but the excessive weed growth associated with eutrophication impacts on water quality, fish stocks and threatens the use of the lake for recreational amenity.   

Lough Gur is situated in an internationally important archaeological landscape and consequently is an important asset to the county historically, environmentally, aesthetically and economically. The area is a proposed National Heritage Area (NHA, 437) and a Wildfowl Sanctuary (WFS-33) and therefore considered of national importance. The area contains a range of EU Habitat Directive (92/43/EEC) priority Annex 1 habitats including transition mires, quaking bog and alkaline fen. The lake has dense summer growths of submerged plants Ceratophyllum and Elodea while reedbeds of Typha latifolia, Carex spp. and Iris pseudacorus dominate the emergent vegetation. Rudd, Perch and Pike are present with Rudd dominant in terms of biomass and Perch in terms of abundance.  

The lake is currently classified as ‘moderate’ status, because of lake plants, fish status and elevated levels of the nutrient total phosphorus.  Ammonia-Total (as N), Chlorophyll and Total Phosphorous (as P) are all indicating an upward trend 2016-2021. Potential sources of nutrients in the Lough Gur catchment include agricultural activities (slurry, fertilizer, manure from animals grazing in or around the lake). Pathways are potentially overland where soils are heavy and via groundwater where soils are well drained but very thin. Seepage of effluent from on-site wastewater treatment systems including septic tanks are another likely source of phosphate to the lake.  

For Lough Gur to reach its WFD objective of Good Ecological status thereby making a significant contribution to improving the quality of all life.  

Identify lake-specific restoration mechanisms.  

An understanding of the nutrient content of the lake sediments, and the dissolved oxygen profile of the lake water to complete a nutrient balance for the lake.  

Identify the nutrient inputs from the surrounding groundwaters and surface rivers and effects on the lake water body.  

Where nutrient inputs have been identified implement targeted measures to reduce this nutrient input and quantify necessary resources, human and financial, to conduct restoration goals.  

Plan provisions for improved liaison with community and local interest groups.  

Work towards improved conservation and management of the natural heritage of the area.  

The primary stakeholders are the local landowners and farmers who own most of the surrounding catchment area. 

The local authority Limerick City & County Council own approximately 10% of the lake shore and operate a visitor centre, public carpark, public toilets and a refreshments kiosk. 

The Local Authority Waters Programme (LAWPRO) works on behalf of Ireland’s 31 local authorities to protect and restore good water quality in our rivers, lakes, estuaries, ground and coastal water through catchment science and local community engagement. 

A voluntary community-based rivers trust is operational in the wider Maigue River Catchment. The Maigue Rivers Trust (MRT) was established in 2016 and has directors drawn from social, economic and environmental interests. The MRT aims to work with local communities to ensure that the rivers and lakes of the Maigue catchment can achieve their full potential both environmentally and recreationally. 

Inland Fisheries Ireland conduct fish stock surveys on the National Research Survey Programme. The most recent survey was on Lough Gur in 2021. 

The Lough Gur Group Water Scheme is public groundwater water supply serving a population of 1,439 with 700 metered water supply connections including domestic, agricultural, and commercial connections.