Lough Funshinagh (Irish: Loch Fuinseann, meaning 'lake of the ash tree') is a lake and Special Area of Conservation (or SAC) in County Roscommon, Ireland, found to the west of Lough Ree. It has been called Ireland's amazing disappearing lake, due to the way it empties quickly - in as little as two days - and unpredictably, sometimes killing thousands of fish. Lough Funshinagh is one of a number of seasonal lakes, or turlough, found in the karst areas of Ireland, west of the River Shannon. The qualifying interests by which it is protected as an SAC are the presence of two specific habitat types:
Turloughs Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation.
Location The Lough Funshinagh SAC is located approximately 12 km from Athlone, County Roscommon and County Westmeath, in the townlands of Ballagh (Electoral District: Carnagh), Carrick (Electoral district: Rockhill), Carrickbeg (Electoral District: Rockhill), Inchiroe and Gortfree, Kildurney, Lisfelim, Lysterfield and Rahara. Schedule 1 of the Statutory Instrument for this SAC (S.I. No. 76/2018) identifies it as encompassing an area of 430.52 hectares.
SAC qualification The Lough Funshinagh site was proposed as a Site of Community Importance (SCI) in November 1997 and designated as a Natura 2000 site in May 2019 under the Habitats Directive. Statutory Instrument No. 211 of 2019, establishing the site as an SAC (Site code: 000611), was passed in 2019. According to the NPWS site synopsis, the features which qualify this site for an SAC designation are the presence of two specific protected habitat types, those of
Turloughs [Natura 2000 code 3180] (Priority Habitat on Annex I of the E.U. Habitats Directive) Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation [Natura 2000 code 3270] The Biodiversity Information System for Europe (BISE) web page for the site notes the sizes of the two protected habitats as: Turloughs: 378.30 ha (3.7830 km²) and Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation: 33.00 ha (0.3300 km²). The BISE webpage for the Lough Funshinagh site notes 13 EU Protected Species occurring at this location – all 13 are bird species.
Other protected status qualifications The National Parks and Wildlife Service (NPWS) has included an area of 480.96 hectares at the Lough Funshinagh site as a proposed Natural Heritage Area or pNHA. Very close to this site, Lough Croan Turlough and Four Roads Turlough SACs have also been included as pNHAs. The site at Lough Funshinagh is a County Geological Site (site code: RO018) and is recommended for a Geological Heritage Area.
Hydrogeology The significant ecological features of the Lough Funshinagh site are described in the National Parks and Wildlife Service site synopsis for the site. In this document, the lake is defined as a turlough. “Lough Funshinagh is located approximately 12 km north-west of Athlone, in Co. Roscommon. The lake, which is underlain by Carboniferous limestone, is classified as a turlough because it fluctuates to a significant extent every year and occasionally dries out entirely (approximately two to three times every ten years. In most years, however, an extensive area of water persists.” Data on groundwater levels are available from the Groundwater Level Data Viewer by Geological Survey Ireland. Data recorded for groundwater levels at the site since August 2016 indicate that peaks in water levels typically occur in Spring (March-April) and levels tend to decrease in the Summer and Autumn. The area at Lough Funshinagh is part of the ‘Athlone chain’ of eskers in the System of Clara, as described in the 1876 Scientific transactions of the Royal Dublin Society. The site synopsis notes that this lake is fed by springs and a small catchment lying to the west. Its trophic state is described as mesotrophic (with an intermediate level of productivity and nutrients) and includes some marl deposition (calcium carbonate deposits).
While the size of the Special Area of Conservation is set, the size of the turlough varies. The hydrogeology of this turlough site results in the typical periodic increases and decreases in turlough size and volume, which have been associated with significant drainage and flooding events. The magnitude of these fluctuations is affected by drainage rates through the karstic landscape, and can be affected by weather events. “While Lough Funshinagh is designated as a turlough due to its characteristic fluctuating water levels, it is extremely slow to drain and seldomly empties completely. The characteristic slow response of Funshinagh means that, unlike other turloughs in Ireland, it does not get the opportunity to reset it’s flood pattern each year. This leaves it particularly vulnerable to weather events as their impacts can carry over from one year to the next.”
Significant drainage events Several significant reductions in size have been described, including in 1955, 1984 and 1996. The lake emptied in effect completely in 1996 – water levels began to drop after 19 August 1996 and by 1 September 1996, there was only approximately 30 cm water remaining in the southern end of the lake, and a few days later, only some pools of water remained, with large numbers of fish stranded. Geological Survey Ireland's County Roscommon Geological Site Report states that the terrain of the lake is karstic in nature, underlaid by Carboniferous limestone bedrock. The report suggests that there may exist thin clay or marl deposits under the bed of the lake. The report also states that the lake bed appears to contain one or more swallow holes. These, it is suggested, are usually blocked by an impermeable layer (for example, a clay layer). The breaking of this ‘seal’ on the swallow hole can lead to rapid draining of the lake. This process will result in a ‘gradual slumping inwards of impermeable material’, blocking the swallow hole again. However, it was noted by Drew and Burke in a Geological Survey Ireland publication in 1996 that:
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