Lough Derg spawning fears over Shannon abstraction

FLUCTUATIONS in water levels in Lough Derg could have a significant impact on the spawning of coarse fish population, if Dublin City Council proceeds with its plan to abstract over 350 million litres of water on a daily basis from the lake, angling groups have warned.
The Shannon Regional Fisheries Board and Lough Derg Anglers made a series of submissions to consultants who have launched a new report detailing the need and way that huge volumes of water could be abstracted from the River Shannon to supply the Dublin region.
In their submissions, they highlighted the impact of low flows on the Fish Pass at Parteen Weir; sought clarification in relation to the low flow modelling carried out in the preferred option; highlighted the need for more information on water levels and retention times and possible adverse affects on biodiversity, fish, angling and tourism.
A number of submissions were concerned the proposed abstraction would impact negatively on future availability of local water supplies. Stakeholders were concerned the abstraction should not be at the expense of local water supplies and sought an assurance that this would not happen or that development in the region would not be restricted.
Concerned residents who contacted the consultants felt the provision of a water supply for the Dublin region shouldn’t be at the expense of local needs.
The IFA sought a management programme to alleviate flooding, while other submissions expressed concern about the impact of high water levels on farming in the Callows and risk of flooding.
Concern about the role of the ESB in the current management of the Shannon, implications of this management regime for the abstraction of water and how the regulation of flow would be achieved were also raised in a number of submissions.
Consultants argued that in the case of the recommended Lough Derg water supply option, potential water level impacts as a result of abstraction could be offset by minor 1 to 2% modifications, subject to ESB agreement to Ardnacrusha’s power generation output.
“Abstractions of water for use within the Shannon catchment, upstream of the proposed abstraction point, have little or no impact on the proposed abstraction since about the same quantity of water is returned back into the river and lake system following treatment.
“Potential future abstractions for local catchment use downstream of the proposed abstraction point are not impacted by the proposed abstraction, as the proposed level of average abstraction is about 2% of Ardnacrusha flow at 2040/2050 and these abstractions are coming by agreement with the ESB from water stored in Lough Derg for use in Ardnacrusha.
“Water flows into the old Shannon River at Parteen Weir, which are used to supply Limerick, are totally unaffected by the abstraction proposals. These flows are managed by the ESB under statute.”
The consultants acknowledged the ESB are legally entitled to financial compensation for loss of water, which could have been used for electricity generation at Ardnacrusha.
They pointed out the recommended water supply option involves maximisation of water abstraction from Lough Derg in high-flow periods, when the ESB potentially are unable to use the water due to flows exceeding Ardnacrusha’s maximum limit of 400m3 per second. The water abstracted during high flow periods will be stored in a former cutaway bog in the Midlands for later dry-period use.
“In this manner, water could potentially be compensation free for high-flow periods of the year depending on flow/climatic conditions.”
The consultants also pointed out agreement with the ESB would be made in writing and these would become part of the planning consent process to be adjudicated by An Bord Pleanála.
They confirmed the proposed maximum abstraction is 4m3 per second, which would have a marginal beneficial impact on flooding.
Lough Derg has a European designation in relation to its ecological habitats and species. However, the consultants believe the proposed abstraction would not result in changes to the current operational lake levels and external storage could be used to manage any residence time issues that may arise during low-flow periods.
They also claimed the proposed abstraction would not impact negatively on water quality or on the ecology of the Shannon/Lough Derg ecosystem and will be in full compliance with the Water Framework Directive. Further detailed assessments including a pollan survey will be carried out during the Environmental Impact Stage (EIA) of this project.
The preferred option involves raw water abstraction from northern Lough Derg and pumping of raw water to a cutaway bog near Portarlington. Combined raw water and treated water pipelines would be about 130km in length. The proposed 2031 level of abstraction for Dublin and Midlands is about 2% of the average Shannon flow in Lough Derg.
The main opponents of the proposed scheme, the Shannon Protection Alliance, have vowed to take their opposition to the project to the European Commission, if necessary.