Select an outfall on the map to see its live state, the rainfall measured at its nearest gauge, and its full history.
The permit test
environment agencyStorm overflows are only permitted to operateduring times of rainfall and snowmelt.
— Environment Agency, permit conditions for storm overflows
So what counts as a dry day? Not our judgement — the Environment Agency's. Their own definition of a dry-day spill is under 0.25 mm of rain on the day of the spill and under 0.25 mm the day before. We use exactly those figures, so anything we call a dry spill is also a dry-day spill by the regulator's own bar.
We then add four checks that can only ever make us less likely to say it: the previous week must have been dry too, the dry condition must have held for 12 hours, the nearest gauge must be within 10 km and reporting in the last 90 minutes, and we must actually hold the week of history we are claiming. Fail any of them and the outfall is marked unverified, never dry.
Rainfall against discharge · last 24 hours
whole regionRain falls from the top; the number of outfalls discharging rises from the bottom. They should move together.