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Potters Bar Brook

A stream near Potters Bar, Hertfordshire. No gauge of its own: what the river map and the banked data say about it.

Potters Bar Brook is a stream on Ordnance Survey’s river map near Potters Bar, Hertfordshire, with about 2.4 km of mapped channel. On the map it flows into Mimmshall Brook, which flows on into the River Colne, then the River Thames and out to the sea.

Next gauge downstream

Mimmshall Brook on Mimmshall Brook, about 20 m along the river below where Potters Bar Brook ends on the map.

0.26 mASD Normal · easing 30 min ago

After that, North Mymms, about 1.4 km along the river.

No gauge measures Potters Bar Brook itself. A gauge downstream shows water that has already passed it, mixed with everything else that has joined on the way, so it says nothing exact about this stream.

Storm overflows on Potters Bar Brook

1 storm overflow is placed on this stream on the river map. Each status is the water company’s own monitor.

Darkes Lane, Potters Bar Not discharging
Thames Water · into Potters Bar Brook · 2025: 9 spills, 25 h

A status says whether an overflow is discharging now, never how much or why. A monitor that is offline or has not reported is not “not discharging”. Sewage in Britain’s rivers →

Live status: © Thames Water storm overflow activity data, licensed under CC BY 4.0. Annual spill figures: Environment Agency Event Duration Monitoring return, © Environment Agency copyright and/or database right, Open Government Licence (OGL) v3.0.

Water-sampling points on Potters Bar Brook

1 Environment Agency sampling point is placed on this stream. These are dated samples taken by hand, not live readings, and FloodRadar does not grade them.

Potters Bar Brook above Mimmshall Brook
No sample published 1 Oct 2023 – 30 Sep 2026

A sample is taken on a date; it says nothing about the water today. A sample below an overflow does not by itself show where anything in it came from.

Water samples: Environment Agency Water Quality Archive, © Environment Agency and/or database right 2026, Open Government Licence v3.0.

Places along it

From its source towards its mouth, the settlements within a kilometre of it on the map: Potters Bar.

On the map

The map needs JavaScript. Everything it shows is listed on this page.

The blue line is Potters Bar Brook; grey lines are other mapped watercourses. Lines from OS Open Rivers (edition 2026-04).

Mimmshall Brook, the river it joins →EN6 3NL, a postcode page near where it ends on the map (about 270 m away) →All rivers with gauges →

What this page can and cannot tell you

Its line, its name and where it flows come from Ordnance Survey’s river map (OS Open Rivers, edition 2026-04), which leaves out many small streams, ditches and culverts. “Flows into” is the map’s word: a channel that is not on the map is not shown here, which does not mean it is not there.
No gauge measures Potters Bar Brook itself, so its own level is not known here.
Storm overflows are listed only where the river map places them on this stream; an overflow it could not place is not counted.
Water samples are England’s only (the Environment Agency’s archive), placed where the map can place their sampling point.
Nothing on this page says whether any place floods. For an address, see its postcode page.

This uses Environment Agency flood and river level data from the real-time data API (Beta). Licence: Open Government Licence v3.0.