The monitoring network within this area

Hydrionis holds 121,022 values from 8 gauges within it. Discharge is a property of a gauge and its reach, not of this drainage area, so this page reports the network and its records rather than a single figure.

8

Gauges

121,022

Values held

1909–2026

Record spans

3,591 km²

Area

Gauges within the Nyköpingsån drainage basin

8 monitoring points, positioned as the publisher records them.

How low, how high and how variable this gauge runs

A hydrograph says what happened; these say how often. Read off HALLBOSJÖN's whole daily record between 1933 and 2026, they describe the shape of the record rather than any day in it — and they belong to this gauge and its reach, not to this drainage area.

1.580 m³/s

Q95 low flow

8.880 m³/s

Q50 median flow

23.900 m³/s

Q10 high flow

Largest day of each water year at HALLBOSJÖN

The highest daily mean discharge in each October-to-September water year, 1933–2025.

These are the largest daily means, not flood peaks. A peak lasting hours is averaged across a whole day here, so the true instantaneous maximum on the same day was higher — sometimes far higher on a fast-responding catchment. Flood frequency work needs a publisher's own instantaneous series; Hydrionis holds one for 2,236 American gauges and not for this one, so the two are never drawn together. A water year the gauge did not substantially cover produces no value at all rather than a low one.

View the data behind this chart

Underlying data
Period	HALLBOSJÖN (m³/s)
1933	9.61
1934	29.4
1935	33.8
1936	38.3
1937	26.0
1938	35.0
1939	15.1
1940	13.9
1941	17.5
1942	26.0
1943	27.5
1944	41.3
1945	18.8
1946	17.8
1947	7.25
1948	5.96
1949	28.3
1950	42.2
1951	21.4
1952	20.8
1953	20.4
1954	24.9
1955	17.5
1956	20.8
1957	37.5
1958	46.3
1959	24.6
1960	45.4
1961	28.3
1962	17.5
1963	20.1
1964	16.9
1965	48.6
1966	35.8
1967	28.6
1968	31.8
1969	26.4
1970	17.5
1971	22.8
1972	11.7
1973	15.7
1974	37.9
1975	2.70
1976	40.5
1977	35.8
1978	25.7
1979	13.3
1980	30.0
1981	40.1
1982	23.7
1983	18.7
1984	36.7
1985	40.3
1986	17.1
1987	37.5
1988	17.1
1989	16.2
1990	19.0
1991	17.1
1992	16.4
1993	26.1
1994	31.2
1995	12.8
1996	25.3
1997	29.7
1998	37.3
1999	21.6
2000	51.5
2001	29.8
2002	13.1
2003	22.1
2004	17.7
2005	25.0
2006	31.1
2007	19.7
2008	28.6
2009	32.6
2010	25.9
2011	21.0
2012	30.8
2013	30.7
2014	25.6
2015	18.8
2016	4.50
2017	25.8
2018	12.0
2019	24.3
2020	24.1
2021	8.70
2022	25.2
2023	41.0
2024	19.5
2025	15.6

The longest record here

Mean river flow at HALLBOSJÖN

Annual means of the daily record, 1934–2025. One gauge, not this drainage area.

Annual means computed by Hydrionis from the published daily record, drawn only for years with at least 300 days held. They summarise this gauge's own record and say nothing about any other watercourse in this area.

View the data behind this chart

Underlying data
Period	HALLBOSJÖN (m³/s)
1934	6.12
1935	13.3
1936	16.8
1937	13.0
1938	9.48
1939	11.7
1940	7.04
1941	6.43
1942	7.32
1943	10.5
1944	17.7
1945	16.2
1946	13.0
1947	8.06
1948	4.75
1949	3.85
1950	12.4
1951	14.8
1952	11.2
1953	11.8
1954	10.0
1955	11.8
1956	8.03
1957	10.8
1958	15.6
1959	16.6
1960	14.6
1961	15.3
1962	15.5
1963	9.89
1964	7.01
1965	9.17
1966	15.9
1967	17.9
1968	12.9
1969	12.2
1970	9.02
1971	8.42
1972	9.60
1973	6.01
1974	9.93
1975	14.7
1976	1.46
1977	15.4
1978	15.2
1979	12.2
1980	11.9
1981	16.7
1982	14.7
1983	10.8
1984	10.7
1985	17.2
1986	16.1
1987	13.1
1988	17.0
1989	6.68
1990	5.98
1991	9.57
1992	6.69
1993	8.38
1994	12.3
1995	17.0
1996	8.61
1997	10.7
1998	16.0
1999	15.3
2000	17.0
2001	18.7
2002	11.9
2003	4.51
2004	10.1
2005	9.52
2006	11.5
2007	12.2
2008	13.1
2009	11.6
2010	16.0
2011	12.4
2012	16.4
2013	13.1
2014	12.1
2015	12.3
2016	8.07
2017	2.84
2018	9.06
2019	4.45
2020	9.25
2021	9.58
2022	4.77
2023	14.3
2024	17.8
2025	7.81

Every gauge Hydrionis holds within this area

Gauges within the Nyköpingsån and what each holds
Gauge	Measures	Values	Record
HALLBOSJÖN	mean river flow	33,967	1933–2026
CHRISTINEHOLMS REGL.DAMM	mean river flow	31,591	1940–2026
SIBRO	mean river flow	15,706	1975–2017
BJURSTORP	mean river flow	15,009	1979–2020
NEDRE TÄCKHAMMAR	mean river flow	10,773	1909–1938
VARBRO	mean river flow	5,964	1979–1995
SIBRO 2	mean river flow	5,174	2012–2026
HEBYLUND KVARNSJÖN	mean river flow	2,838	2018–2026

How these gauges were attached to this water

Assigned by the publisher to a numbered basin Every gauge here is assigned to this drainage area by its own publisher, which issues the area an official code — 65000. A drainage area is not a river: it contains the tributaries as well as the main channel, and a gauge in it may be on any of them.

What each gauge’s link to this water rests on
Gauge	Evidence	Established
HALLBOSJÖN	Stated by the publisher on the record this gauge’s observations came from.	With the observations
CHRISTINEHOLMS REGL.DAMM	Stated by the publisher on the record this gauge’s observations came from.	With the observations
SIBRO	Stated by the publisher on the record this gauge’s observations came from.	With the observations
BJURSTORP	Stated by the publisher on the record this gauge’s observations came from.	With the observations
NEDRE TÄCKHAMMAR	Stated by the publisher on the record this gauge’s observations came from.	With the observations
VARBRO	Stated by the publisher on the record this gauge’s observations came from.	With the observations
SIBRO 2	Stated by the publisher on the record this gauge’s observations came from.	With the observations
HEBYLUND KVARNSJÖN	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 3 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	8	yes, 3 or more
Years spanned	118	yes, 20 or more
Values held	121,022	yes, 1000 or more
Distinct measurements	1	no
Publishers measuring it	1	no
Official identifiers	2	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/se-smhi-1273.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.

Data from Sveriges meteorologiska och hydrologiska institut, used under CC BY 4.0.

Sveriges meteorologiska och hydrologiska institut — CC BY 4.0 (licence text)

Suggested citation for Hydrionis

Hydrionis (2026), Nyköpingsån gauge records, accessed 2026-10-05, hydrionis.com/waters/sweden-nykopingsan/

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 Nyköpingsån 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

MeasuredMedium confidence2026-09-30

Source: SMHI — Swedish hydrological observations, 1273. Licence: Open — attribution required (attribution required).

Method: Daily discharge exactly as SMHI publishes it, from its corrected archive. SMHI computes the daily value from its own sub-daily measurement and rating curves; Hydrionis does not recompute it, because a mean derived from whatever sub-daily data happens to be exposed would be a different statistic under the same name.

Checked and approved by SMHI except 1933-10-01 to 1960-12-31 (not yet checked), 1979-06-07 to 1979-06-07 (not yet checked), 2026-02-12 to 2026-09-30 (not yet checked). Station in the NYKÖPINGSÅN main drainage basin, 1,992 km². Discharge is a property of this gauge and this reach, not of the river as a whole.

Retrieved 1 October 2026.