Wales · Natural Resources Wales
Llanishen Reservoir
Avoid swimming
Currently downstream of an active sewage discharge on the river network — Welsh Water (via sewage-map).
High confidence — an active discharge is being reported right now — the event itself is fresh evidence.
Status computed 27 Aug 2026, 06:43 UTC; statuses refresh every 15 minutes.
What we know
- Regulator classification
- Excellent
- Pollution risk forecast
- Not published for this spot
- Active discharges
- None within 5km
- Recent discharges (last 48 hours)
- 1 within 5km
- Upstream river network
- Downstream of an active Welsh Water discharge right now
- Surrounding overflow coverage
- Within an ingested water company network
- Monitoring season
- Currently in regulator monitoring season
Last sampled 6 August 2026 · 7 weeks ago. Source: Natural Resources Wales.
Risk forecasts are published for 14% of Welsh spots only.
Most recent at Ball Lane Storm Overflow (Welsh Water) — ended 26 Aug 2026, 05:40 UTC.
Sewage-map data as of 27 Aug 2026, 06:30 UTC — discharges traced through the river network.
What this verdict means
Avoid swimming is driven by the strongest negative signals this map tracks: an active sewage discharge affecting this water, or a regulator classification of Poor or a closure. After a discharge ends, waiting at least 48 hours before swimming is the standard advice.
Every verdict here is computed from regulator classifications, sample dates, pollution-risk forecasts, and water-company discharge reports — it is not a water test. Absence of a negative signal is not positive confirmation of safety, and conditions on the day (rainfall, currents, cold) matter as much as water quality. Read how statuses are decided.