River Basin Management Plan consultation designates 466 heavily modified water bodies
The Department of Housing, Local Government and Heritage has designated 466 water bodies across Ireland as heavily modified water bodies (HMWBs), a key development in the implementation of the third River Basin Management Plan (2022-2027).
This designation follows a comprehensive technical assessment by the Environmental Protection Agency (EPA) in 2022 and reflects a significant evolution in the State’s approach to water resource management. Previously, only 33 water bodies had been designated as HMWBs. The expansion to 466 water bodies comprises 433 rivers, 20 lakes, and 13 estuarine or coastal waters.
The Department says that this expansion “recognises the longstanding hydromorphological alterations required” to support essential human uses such as flood protection, navigation, water supply, urban infrastructure, and arterial drainage.
Under the EU Water Framework Directive (WFD), HMWBs are those whose physical characteristics have been significantly altered for a specified use, making the achievement of good ecological status (GES) impractical without causing disproportionate socioeconomic or environmental harm. Instead, these water bodies are assessed against the alternative objective of good ecological potential (GEP).
The Department’s review, informed by additional data from specified use owners, determined that in all 466 cases, achieving GES would either “compromise vital services” or prove “technically or financially unviable”. These findings are designed to ensure that the RBMP’s objectives remain aligned with both environmental goals and Ireland’s infrastructural realities.
Going ahead, HMWBs must be integrated into regulatory, planning, and licensing frameworks. The EPA is to define and monitor GEP targets using the mitigation measures (Prague) approach, emphasising improvements where feasible while safeguarding critical human uses.
The designation will be revisited in future planning cycles as national policy evolves particularly in areas such as arterial drainage, land use, and flood management, and as ecological assessment tools become more refined.
The public consultation on the designation of Heavily Modified Water Bodies closed on 23 May 2025, following an eight-week period for stakeholder engagement. The outcomes of this process will inform the finalisation of the third-cycle River Basin Management Plan (RBMP), which covers the period 2022-2027.
The Department of Housing, Local Government and Heritage is expected to publish the final RBMP later in 2025, with implementation of the updated measures to commence shortly thereafter. Planning for the fourth-cycle RBMP (2028-2033) is to begin during this cycle, with consultation and technical groundwork expected to start as early as 2026.
