How To Object
River Lagan and Belfast Lough: Choked by Sewage, Strained by Agriculture
The River Lagan is under siege. Flowing from the green fields of County Down into the heart of Belfast, its journey ends in Belfast Lough, a site protected under international conservation law. But both river and lough are being poisoned.
The culprits? A crumbling sewage infrastructure and poorly regulated agricultural runoff.
Sewage Overload
The River Lagan suffers from a legacy of outdated Combined Sewer Overflows (CSOs), designed to dump untreated sewage into rivers during periods of heavy rain. With increasing rainfall and urban growth, these CSOs are no longer an emergency measure—they are a routine source of pollution.
NI Water admits that Belfast Lough is chiefly polluted by the city’s sewage. Their 2024 report, The Scandal of Belfast Lough, lays bare the truth: download the PDF.
Community reports along the Lagan describe cloudy, grey water, floating debris, and foul smells after storms. In short: the river is sick, and sewage is a major cause.
Read more:
Farm Runoff: A Rural Burden
Further upstream, the Lagan flows through agricultural land. Here, the river absorbs phosphorus and nitrogen from fertilisers and slurry. These nutrients feed algal blooms, smother oxygen levels, and diminish insect and fish populations.
While farming does contribute to river pollution, recent research shows that sewage may be the greater threat to riverine biodiversity. A 2023 Oxford University study found that even treated sewage has a more damaging impact on river ecosystems than agricultural runoff:
This doesn’t mean agricultural pollution gets a free pass. But it means prioritising investment in sewage treatment is crucial for ecological recovery.
Belfast Lough: A Protected Zone Under Pressure
Belfast Lough is a Ramsar site, a Special Protection Area (SPA), and includes several Areas of Special Scientific Interest (ASSIs). Yet protected status hasn’t shielded it from damage. In 2023 and 2024, multiple reports documented high levels of E. coli, sewage debris washing ashore, and increased algae growth.
How Much Sewage Is Going Unmonitored?
NI Water plans to install over 700 Event Duration Monitors (EDMs) by 2027—just 30% coverage of Northern Ireland’s storm overflows. That leaves around 1,633 overflows unmonitored. So how much untracked sewage might be pouring into rivers and loughs?
Estimated Annual Discharge from Unmonitored Overflows:
- Overflows unmonitored: ~1,633
- Average spills per year per overflow: ~41
- Average volume per spill: ~100,000 litres
That equates to approximately 6.7 billion litres of sewage entering our waterways every year without being measured, managed or reported.
No data. No accountability.
Why This Matters Now
This is a keystone moment. If developments like the one at Quarterlands can be halted due to their impact on an already overwhelmed sewage system and vulnerable waterbodies, it could set a precedent.
Groups along the Lagan are starting to organise. Voices are rising. The more we draw attention to the link between development, river health, and lough degradation, the more likely we are to secure meaningful change.
What You Can Do
- Share this post.
- Write to your councillor.
- Ask NI Water why our rivers are treated as open sewers.
The River Lagan can recover. But only if we stop ignoring the pipes beneath our feet.
