Willow Brook — monitoring and records

The monitoring network on this water

Hydrionis holds 2,246 values from 6 gauges on this water. Discharge is a property of a gauge and its reach, not of this water as a whole, so this page reports the network and its records rather than a single figure.

Gauges

2,246

Values held

1938–2026

Record spans

Gauges on the Willow Brook

6 monitoring points, positioned as the publisher records them.

The seasonal shape

An annual mean says how much water a river carried. A monthly record says when — and on most rivers the difference between a wet winter and a dry summer is larger than the difference between one year and the next.

Monthly mean flow at Willow Brook at Willow Brook

Each month's mean discharge as the publisher computed it, which shows the seasonal shape an annual mean flattens away. 1938–2026.

Show relevant events (4 events)Shading marks when something was recorded, not what caused the line.

Taken as the publisher computes it rather than recomputed by Hydrionis from daily values: the publisher knows which of its readings passed validation. Months the gauge did not cover are absent rather than interpolated, and the line breaks where they fall.

What the shaded periods are (4 events)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

Event	Type	Period	Standing	Authority
The 1976 drought	Drought declaration	1975-05-01 – 1976-08-31	Documented record	Compiled record
Yorkshire drought	Drought declaration	1995-04-01 – 1996-03-31	Documented record	Compiled record
The 2022 drought	Drought declaration	2022-03-01 – 2022-10-31	Documented record	Compiled record
European drought	Drought declaration	2022-05-01 – 2022-10-31	Documented record	Compiled record

Not shown on this chart

Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Hurricane Katrina water and sanitation collapse — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.

View the data behind this chart

Underlying data
Period	Willow Brook at Willow Brook (m³/s)
1938	0.218
1939	2.89
1940	0.568
1941	1.79
1942	0.803
1943	0.884
1944	0.268
1945	0.665
1946	0.402
1947	1.37
1948	0.552
1949	0.850
1950	0.423
1951	1.16
1952	0.938
1953	0.831
1954	0.427
1955	1.50
1956	0.803
1957	0.638
1958	1.38
1959	2.01
1960	1.21
1961	1.78
1962	1.29
1963	0.616
1964	0.591
1965	0.630
1966	1.19
1967	1.15
1968	1.40
1969	1.97
1970	1.46
1971	1.49
1972	1.03
1973	0.715
1974	0.838
1975	1.27
1976	0.617
1977	1.81
1978	1.26
1979	1.18
1980	1.04
1981	0.878
1982	1.31
1983	0.899
1984	1.15
1985	0.992
1986	1.44
1987	1.06
1988	1.90
1989	0.643
1990	0.782
1991	0.735
1992	0.854
1993	1.37
1994	1.72
1995	1.51
1996	0.876
1997	0.178
1998	1.49
2000	1.70
2001	1.51
2002	0.868
2003	2.01
2004	1.37
2005	0.779
2006	0.670
2007	1.28
2008	1.42
2009	1.06
2010	1.11
2011	0.893
2012	0.544
2013	1.37
2014	1.78
2015	1.02
2016	1.33
2017	0.729
2018	1.07
2019	0.546
2020	1.54
2021	2.54
2022	0.714
2023	1.28
2024	2.22
2025	1.51
2026	1.97

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	Environment Agency — Hydrology Data Explorer API · Open Government Licence v3.0
How the values came to exist	Measured
Period held	1938–2026
Completeness	98.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	One period inside 1938–2026 holds no value: 1999. It is drawn as a break in the line and is never interpolated across.
Continuity	The record begins in 1938 and is not continuous from it: 89 years separate the first value from the last, and 99% of the years between them are held. The span is not the record.
Last read from the publisher	2026-08-24
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

Every gauge Hydrionis holds here

Gauges on the Willow Brook and what each holds
Gauge	Measures	Values	Record
Willow Brook at Willow Brook	mean river flow, mean monthly river flow	1,096	1938–2026
WILLOW BROOK	ept family richness, life flow index (family level), proportion of sediment-sensitive invertebrates, whpt average score per taxon, whpt number of scoring taxa	370	1985–2025
WILLOW BROOK	ept family richness, life flow index (family level), proportion of sediment-sensitive invertebrates, whpt average score per taxon, whpt number of scoring taxa	220	1989–2013
WILLOW BROOK	ept family richness, life flow index (family level), proportion of sediment-sensitive invertebrates, whpt average score per taxon, whpt number of scoring taxa	190	1985–2013
WILLOW BROOK	ept family richness, life flow index (family level), proportion of sediment-sensitive invertebrates, whpt average score per taxon, whpt number of scoring taxa	185	1995–2013
WILLOW BROOK	ept family richness, life flow index (family level), proportion of sediment-sensitive invertebrates, whpt average score per taxon, whpt number of scoring taxa	185	1988–2025

How these gauges were attached to this water

Named by the publisher Each gauge here names this water in the publisher’s own station record. Hydrionis has not inferred the connection from station names.

What each gauge’s link to this water rests on
Gauge	Evidence	Established
Willow Brook at Willow Brook	Stated by the publisher — Environment Agency hydrology station register, riverName field — https://environment.data.gov.uk/hydrology/id/stations	2026-08-26
WILLOW BROOK	Stated by the publisher on the record this gauge’s observations came from.	With the observations
WILLOW BROOK	Stated by the publisher on the record this gauge’s observations came from.	With the observations
WILLOW BROOK	Stated by the publisher on the record this gauge’s observations came from.	With the observations
WILLOW BROOK	Stated by the publisher on the record this gauge’s observations came from.	With the observations
WILLOW BROOK	Stated by the publisher on the record this gauge’s observations came from.	With the observations

What this record holds

Hydrionis decides which waters get a page, and which of those are offered to search, from what is actually held rather than from how the page reads. Five signals are counted; this record has 5 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	6	yes, 3 or more
Years spanned	89	yes, 20 or more
Values held	2,246	yes, 1000 or more
Distinct measurements	7	yes, 2 or more
Publishers measuring it	2	yes, 2 or more
Official identifiers	1	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/gauge-ea-cf3b4439-a244-41c8-b3e6-089f5ba5cee2.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

No bulk download is offered here, which is a licence position rather than a product one: at least one contributing publisher does not permit redistribution. The values can be read on the page, cited, and pointed to at source.

Attribution and citation

Attribution you are required to give

These are conditions of the licences the underlying data is published under. They are obligations to the publishers, not to Hydrionis, and they apply to you directly whether or not you mention Hydrionis at all.

Contains public sector information licensed under the Open Government Licence v3.0.

Environment Agency — Open Government Licence v3.0 (licence text)

Suggested citation for Hydrionis

Hydrionis (2026), Willow Brook gauge records, accessed 2026-09-02, hydrionis.com/waters/england-willow-brook/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: the Willow Brook gauge records changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

Where these figures come from

Spatially aggregatedHigh confidence2025

Source: EA — Hydrology Data Explorer API, EA measure cf3b4439-a244-41c8-b3e6-089f5ba5cee2-flow-m-86400-m3s-qualified. Licence: Open — attribution required (attribution required).

Method: Mean of the twelve monthly means for the year. Computed from months rather than from daily readings directly, so that a year with uneven observation is not weighted toward its best-observed months. Years with any month missing are not published.

Aggregated by Hydrionis from daily mean flow published by the Environment Agency under the Open Government Licence v3.0.

Retrieved 24 August 2026.