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Live levels from 1 monitoring station across Central Bedfordshire, updated every 15 minutes.
| Station | Level now | Status |
|---|---|---|
| Arlesey | 0.09 mASD 1h ago | Low |
Stations are listed from source to mouth as the water flows, traced on the river map (OS Open Rivers) and the Environment Agency’s own links between its gauges. A distance “by river” is along the river, and is shown only where the map traces the path.
Contains OS data © Crown copyright and database rights 2026.
Streams and rivers with a gauge whose water joins the Hiz above one of its gauges, from the source down. Named streams without a gauge that have a page here are listed at the end.
No gauged tributary joins the Hiz above Arlesey on the river map. Streams without a gauge are not counted here.
Below Arlesey, its water next reaches Biggleswade, a gauge on River Ivel, 8.4 km by river downstream.
Tributaries and where they join are traced on the river map (OS Open Rivers, edition 2026-04) and the Environment Agency’s links between its gauges. The map holds distances between gauges, not the junctions themselves, so a junction is placed between two gauges, and no further up than the tributary’s own lowest gauge. Contains OS data © Crown copyright and database rights 2026.
6 storm overflows are traced upstream of Arlesey, the Hiz’s lowest gauge on the river map: on the Hiz itself, on its gauged tributaries, and on smaller streams that join above there.
Official figures for 2025, for the overflows traced upstream of Arlesey: 27 spills over 109 hours in total, across all 6.
Each overflow is listed in the stretch above the first gauge its water reaches, from the source down, as on the Gauges tab. A stretch of the Hiz includes the smaller streams that join it there.
Within 3 km of one of the Hiz’s gauges in a straight line, but the river map cannot say whether their water reaches it.
3 other overflows within 3 km of these gauges are placed below the Hiz’s lowest gauge or on another river, so not listed.
A status is the water company’s own monitor: it says whether an overflow is discharging, never how much or why, and a spill does not by itself explain a change in a river level. A status older than two hours is shown as unknown. Annual figures are the official returns: 12/24-hour spills for England and Wales, overflow events for Scotland (Scottish Water counts differently, so the two cannot be compared). “No data” means the monitor produced no usable data that year, not zero. Overflows are placed on OS Open Rivers (edition 2026-04), which leaves out many small channels: an overflow the map cannot place may still drain here. Contains OS data © Crown copyright and database rights 2026. Sewage in Britain’s rivers →
Live status: © Anglian Water storm overflow activity data, licensed under CC BY 4.0. Annual figures for England: Environment Agency Event Duration Monitoring return, © Environment Agency copyright and/or database right, Open Government Licence v3.0.
Dated samples taken by the Environment Agency, not live readings. Results are published days to months after the sample is taken, and many points are sampled only a few times a year, or have not been sampled for years.
6 sampling points on the River Hiz and the streams that join it above Arlesey. 4 have a sample from the last 12 months; 4 have any sample banked. Listed from the source down, grouped by the next gauge each one's water reaches.
| Sampling point | Watercourse (map) | Above the gauge | Last sample | Latest results (river water) |
|---|---|---|---|---|
| Ash Brook A602 Road Bridge Ashbrook | Ash Brook | 13 km | 3 Jul 2026 · 3 months ago | |
| River Hiz Road Bridge Biggin Lane Hitchin | River Hiz | 11 km | 3 Sep 2026 · 35 days ago | Oxygen 87.7%Temp 15.9 °CpH 7.92Ammonia 0.067 mg/l |
| River Purwell A505 Road Bridge Hitchin | River Purwell | 11 km | 3 Sep 2026 · 35 days ago | Oxygen 82%Temp 14.6 °CpH 7.52Ammonia below 0.03 mg/l |
| River Hiz upstream of Hitchin sewage treatment works | River Hiz | 8.7 km | Last sampled 26 Feb 2020, before the imported period | |
| River Hiz Cadwell Arch | River Hiz | 7.2 km | Last sampled 13 Jan 2020, before the imported period | |
| Stondon Brook A600 Road Bridge Holwellbury | unnamed stream | 4.9 km | 4 Sep 2026 · 34 days ago | Oxygen 28.4%Temp 17.6 °CpH 8.21 Mar 2026Ammonia 0.062 mg/l |
Distances are along the river to the gauge named. England's samples only.
FloodRadar does not grade these results: there is no overall score, and official river classifications are a separate dataset. A sample taken downstream of an overflow does not by itself show where anything in it came from. River connections and distances are traced on OS Open Rivers (edition 2026-04), which leaves out many small channels.
Water samples: Environment Agency Water Quality Archive, © Environment Agency and/or database right 2026, Open Government Licence v3.0.
Contains OS data © Crown copyright and database rights 2026.
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