1001 Smart Cities
🇩🇰 Copenhagen

Copenhagen Bathing Water Forecast & Overflow Warning System

🤖 AI-generated summary · ◆ 15 sourced claims · 🔎 Last verified

This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.

15 sourced claims on this page, none individually verified yet — turn on “Sources in the text” to see each one.

How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page

✎ Updated 14 Oct 2026 1 source added. What changed →

A rainfall and sewer-overflow model decides whether the harbour baths open. Running since 2002 under consultancy DHI with the city and utility HOFOR, it raises red flags for bacteria risk after storms.

Outcome🎯 Succeeded
Evidence🏛️ Official
what does this mean?The strongest source is the operator's or the city's own reporting — an official report, dataset or press release. It grades who did the looking — not how well the project went. All four grades →
Run byCity of Copenhagen & HOFOR (system developed by DHI)
Scale🏙️ City-wide

Part of 1001 Smart Cities — 1,216 documented projects · 🏙️ 9 more in Copenhagen · 💧 Water guide · 📡 Data & IoT projects

Since 2002, Copenhagen's harbour baths have been covered by a bathing-water forecast system developed by DHI with the City of Copenhagen and water utility HOFOR. A predictive model combines rainfall data with the utility's overflow data to estimate bacteria risk after storms, triggering red-flag closures shown on badevand.dk. The city approved a new digital warning system in April 2021 and its record names only the operator that runs it; a closure in April 2025 confirms the warnings are still issued.

Live 📅 since 2002

📊 Impact

The warnings closed Islands Brygge harbour bath for 125 hours in the 2025 season, 4.2% of the time, and the bath's water was rated excellent in every year from 2022 to 2025 on samples taken at least 20 times a year.

🎓 Lesson

A forecast is worth what it lets a city open: Copenhagen's 2021 digital system removed the cap on how many harbour bathing sites the warnings could cover, let sites reopen 7 hours after an all-clear instead of 12, and allowed them 180 metres from an overflow instead of 200.

📡 Data & IoTWaterSensors & IoTHealth & care

Sources

↗ DHI — Safe bathing water in the heart of Copenhagen HarbourDeveloper's project page: DHI built the Bathing Water Forecast system with the City and HOFOR (provider of the sewer data); MIKE 11/MIKE 3 FM/ECO Lab model chain predicts E. coli and enterococci; warnings by website, SMS and managers' dashboards.
↗ City of Copenhagen (kk.dk) — update of the bathing-water warning systemPublished 12 April 2021Committee record of 12 April 2021, approved without a vote: the almost 20-year-old warning system made digital so more bathing sites can be created; red flashing lamps, warning time at most 20 minutes, reopening after 7 hours instead of 12, overflow distance 200 m to 180 m, bathing-water wardens wound down from 2022.
↗ The Local Denmark — sewage overflow closes Copenhagen harbour baths (April 2025)Published 23 April 2025Authorities advised against swimming in most of the harbour after Biofos accidentally discharged 12,000 cubic metres of sewage; red flags on badevand.dk and red warning signs at the baths.
↗ City of Copenhagen (kk.dk) — bathing-water profile, Islands Brygge Havnebad (2026 season)Municipal bathing-water profile for the 2026 season: the site is covered by the forecast with an on-site lamp; overflow structures about 200 m away; water rated excellent 2022–2025; closed 125 hours (4.2%) in the 2025 season; sampled at least 20 times a year.
Show your work What this page rests on and what it can’t tell you · all 15 claims with their sources · the forensic record

Evidence file · public beta 15 addressable claims, 4 source dossiers, one permanent baseline. The file is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.

Inspect the claims, one by one — verbatim text, sources and caveats for all 15

The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.

Claim 1 clm-c70c609c107d35de quantitative
Since 2002
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The municipal committee record of 12 April 2021 dates the warning system by its age rather than by a start year: "Det nuværende varslingssystem er snart 20 år gammelt" ("The current warning system is almost 20 years old"), which places its introduction around 2001 or 2002.
Caveat
No listed source names the year 2002. It is inferred from a 2021 municipal record that calls the warning system almost twenty years old, and the developer's own project page gives no start year at all. DHI's page, carrying a 2023 publication stamp, says residents have used the harbour bath 'for almost twenty years'.

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 2 clm-c9b5c20db7c75f8d descriptive
a bathing-water forecast system developed by DHI
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
DHI's project page describes the system and its own role: "DHI - in collaboration with the City and HOFOR (the provider of the sewer data) - developed an innovative Bathing Water Forecast (BWF) system", and says the system "constantly monitors the harbour's water and predicts the concentration of the indicator bacteria Escherichia coli and Enterococci at specified locations". The page lists the City of Copenhagen as its client.
Caveat
This is the developer's own project page and therefore promotional material. It says DHI developed the system; "has run" is stronger than anything the page states, and the municipal record refers only to "the operator that runs the warning system" without naming DHI.

Sources carrying this claim

  1. DHI — Safe bathing water in the heart of Copenhagen Harbour
Claim 3 clm-14daa91753b25154 descriptive
with the City of Copenhagen and water utility HOFOR
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The developer's page names all three parties: the system was built "in collaboration with the City and HOFOR (the provider of the sewer data)", with the City of Copenhagen listed as client. The municipal record confirms the city's part: the Technical and Environmental Administration supervises the bathing water, is responsible for warning bathers, and "har kontrakten med den operatør, som driver selve varslingssystemet" ("holds the contract with the operator that runs the warning system").
Caveat
HOFOR appears only as the supplier of the sewer data, not as an operator of the forecast, and the municipal record does not mention HOFOR at all.

Sources carrying this claim

  1. DHI — Safe bathing water in the heart of Copenhagen Harbour
  2. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 4 clm-42e8ed334c5d2df4 descriptive
A predictive model combines rainfall data with the utility's overflow data
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The developer's page sets out the model chain: "DHI collects meteorological data from forecast suppliers and runs hydrodynamic models", feeding "a MIKE 11 (now MIKE+ Rivers) model to estimate the inflow of water from the city into the harbour", then "a MIKE 3 FM model calculating the transport of pollutants and a MIKE ECO Lab model for describing the fate of the bacteria". HOFOR is named as the provider of the sewer data, and the municipal record says the replacement system "har opdaterede data om overløb" ("has updated data on overflows").
Caveat
The developer's page describes meteorological forecast data rather than measured rainfall, and no listed source states that the sewer input comes from overflow sensors: the sewer data is only attributed to the water utility.

Sources carrying this claim

  1. DHI — Safe bathing water in the heart of Copenhagen Harbour
  2. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 5 clm-d1fc47b1ccd37e0a descriptive
to estimate bacteria risk after storms
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The developer's page names the threats as "heavy rainfall, frequent release of sewage water and induced pathogenic bacteria", and says the system "predicts the concentration of the indicator bacteria Escherichia coli and Enterococci at specified locations along the water courses from the city to the harbour".
Caveat
Rain-driven overflow is one cause among several. The April 2025 closure reported in the press followed an accidental discharge from a treatment plant, not a storm.

Sources carrying this claim

  1. DHI — Safe bathing water in the heart of Copenhagen Harbour
Claim 6 clm-2d821d02501eab58 descriptive
triggering red-flag closures
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The municipal record describes what the 2021 update changed: warnings are now given by additional warning signs and "røde lamper, der blinker ved forureninger" ("red lamps that flash during pollution events"), with a warning time of at most 20 minutes; the bathing-water wardens who used to hoist the flags are no longer needed for this ("det ikke er nødvendigt med badevandsvagter til at sætte flag") and were wound down from 2022, and sites reopen seven hours after "systemet har sagt god for badning" ("the system has cleared bathing"). The press report shows the effect in April 2025: red flags on the forecast site, and "Red warning signs have been placed at the harbour baths by Copenhagen Municipality".
Caveat
What follows is an advisory rather than an enforced closure: bathers are warned and advised not to swim, and the harbour itself is not shut. The rules the warning runs on - the safety distance to an overflow point and how long a site stays closed - are set by the city administration, and the developer's page describes its dashboards as helping authorities "make informed and timely decisions" rather than acting alone.

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
  2. The Local Denmark — sewage overflow closes Copenhagen harbour baths (April 2025)
Claim 7 clm-8c67294cbc098540 descriptive
shown on badevand.dk
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The article states that Denmark's water quality forecast, which can be viewed on badevand.dk, "shows a chain of red flags around the coast of Copenhagen".
Caveat
badevand.dk is the national Danish bathing-water site, which the article describes as Denmark's forecast rather than a service of the City of Copenhagen.

Sources carrying this claim

  1. The Local Denmark — sewage overflow closes Copenhagen harbour baths (April 2025)
Claim 8 clm-e700c58d2855bda9 quantitative
The city approved a new digital warning system in April 2021
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The Technical and Environmental Committee was asked to approve that the administration "implementerer ændringer i varslingssystemet for badevand, så der kan oprettes flere badesteder og systemet bliver digitalt"; the record of 12 April 2021 states: "Indstillingen blev godkendt uden afstemning."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 9 clm-41515ea0f6a34d1d descriptive
its record names only the operator that runs it
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The record says the administration "har kontrakten med den operatør, som driver selve varslingssystemet" ("holds the contract with the operator that runs the warning system itself") without naming the operator.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 10 clm-b2ffc43e1ab78ea3 quantitative
a closure in April 2025 confirms the warnings are still issued
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Published on 23 April 2025, the article reports that "Danish authorities currently advise against swimming in most of Copenhagen Harbour" after the wastewater company Biofos "accidentally discharged 12,000 cubic metres of sewage into a stream which flows directly into the harbour", with red flags visible on badevand.dk and red warning signs placed at the baths by the municipality.
Caveat
The article describes an advisory against swimming rather than a formal closure, and the cause was an accidental discharge from a treatment plant rather than a storm overflow.

Sources carrying this claim

  1. The Local Denmark — sewage overflow closes Copenhagen harbour baths (April 2025)
Claim 11 clm-13dc3693159b177c quantitative
The warnings closed Islands Brygge harbour bath for 125 hours in the 2025 season, 4.2% of the time
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The city's 2026 bathing-water profile: "Badestedet var i badesæsonen 2025 i alt lukket 125 timer (rødt flag), svarende til 4,2 % af tiden." It also says the site is part of the bathing-water forecast, which warns on the basis of predictions, with a lamp on site.
Caveat
Closure hours measure how often the forecast warned, not whether each warning was right; no listed source publishes the forecast's hit rate.

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — bathing-water profile, Islands Brygge Havnebad (2026 season)
Claim 12 clm-d501fed228c9a6b4 quantitative
the bath's water was rated excellent in every year from 2022 to 2025 on samples taken at least 20 times a year
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The profile's quality table rates bathing water at DKBW 1525 "Udmærket" (excellent) for 2022, 2023, 2024 and 2025, and states that supervision is carried out "Ved prøveudtagning (minimum 20 gange per år)".
Caveat
The classification and the sampling are the municipality's own; they cover water quality at the bath, which also depends on the city's overflow reductions, not only on the warnings.

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — bathing-water profile, Islands Brygge Havnebad (2026 season)
Claim 13 clm-63fd8e6512261546 quantitative
Copenhagen's 2021 digital system removed the cap on how many harbour bathing sites the warnings could cover
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
"Det væsentligste resultat er, at systemet ikke længere sætter en begrænsning for, hvor mange badesteder, der kan oprettes i havnen." The old system, built for a few sites, had reached its maximum capacity with 13 bathing sites.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 14 clm-6fd4ebbed5c9aed2 quantitative
let sites reopen 7 hours after an all-clear instead of 12
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The approved recommendation: "badestederne åbnes 7 timer efter systemet har sagt god for badning mod 12 timer i dag".
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Claim 15 clm-f3c49850d653bc22 quantitative
allowed them 180 metres from an overflow instead of 200
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
"afstanden mellem overløb og badesteder kan reduceres fra 200 meter til 180 meter, på baggrund af konkrete vurderinger", justified by the more visible warning and the fact that overflows usually happen in heavy rain, when nobody bathes.
Caveat
The shorter distance applies only after a site-by-site assessment.

Sources carrying this claim

  1. City of Copenhagen (kk.dk) — update of the bathing-water warning system
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders

This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.

unreviewed Revision 2026-10-14-success-audit effective 2026-10-14 · created 2026-10-14

Awaiting operator and domain-expert review; publication of this revision implies neither.

sha256:e0e7b17c8e1950b6f2496cd73a656b5e0bebdbb676a579d0473849c033ae89c9
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
15
of 15 claims mapped
4
source dossiers
2
publication dates recorded
0
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
City of Copenhagen & HOFOR (system developed by DHI)
Actor types
city-government, utility
Funding model
public
Funding description
Not recorded
Cost
Not recorded
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

4 source dossiers

DHI — Safe bathing water in the heart of Copenhagen Harbour dhigroup.com · 4 linked claims

Open original source ↗

Stable source ID
src-41e0cde0a10c8b78
Publisher
Name not classified · dhigroup.com
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Developer's project page: DHI built the Bathing Water Forecast system with the City and HOFOR (provider of the sewer data); MIKE 11/MIKE 3 FM/ECO Lab model chain predicts E. coli and enterococci; warnings by website, SMS and managers' dashboards.

Descriptive only — not page/paragraph exact
Claims linked
City of Copenhagen (kk.dk) — update of the bathing-water warning system kk.dk · 9 linked claims

Open original source ↗

Stable source ID
src-7d1bb9cffc4460ad
Publisher
Name not classified · kk.dk
Type / language
web-page · language not classified
Published
2021-04-12
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Committee record of 12 April 2021, approved without a vote: the almost 20-year-old warning system made digital so more bathing sites can be created; red flashing lamps, warning time at most 20 minutes, reopening after 7 hours instead of 12, overflow distance 200 m to 180 m, bathing-water wardens wound down from 2022.

Descriptive only — not page/paragraph exact
Claims linked
The Local Denmark — sewage overflow closes Copenhagen harbour baths (April 2025) thelocal.dk · 3 linked claims

Open original source ↗

Stable source ID
src-efa41a7f83c1910b
Publisher
Name not classified · thelocal.dk
Type / language
web-page · language not classified
Published
2025-04-23
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Authorities advised against swimming in most of the harbour after Biofos accidentally discharged 12,000 cubic metres of sewage; red flags on badevand.dk and red warning signs at the baths.

Descriptive only — not page/paragraph exact
Claims linked
City of Copenhagen (kk.dk) — bathing-water profile, Islands Brygge Havnebad (2026 season) kk.dk · 2 linked claims

Open original source ↗

Stable source ID
src-4afe05295b3426d6
Publisher
Name not classified · kk.dk
Type / language
pdf · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Municipal bathing-water profile for the 2026 season: the site is covered by the forecast with an on-site lamp; overflow structures about 200 m away; water rated excellent 2022–2025; closed 125 hours (4.2%) in the 2025 season; sampled at least 20 times a year.

Descriptive only — not page/paragraph exact
Claims linked
Known limits of this file
  • Publisher names and source languages have not yet been classified; domains are recorded without guessing.
  • Existing source notes are descriptive locators, not page- or paragraph-exact citations.
  • A missing archive, publication date or content hash is shown as null rather than inferred.
  • The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.

Continue exploring

Compare this project

🇵🇭 Pasig River: Court-Ordered Water Quality Monitoring · Manila Manila's court set the same swimmable bar for the Pasig in 2008; eighteen years on, sewage still dominates its fecal load. 🇨🇴 SIATA Early Warning Network · Medellín Same genre as Medellín's SIATA — a measurement network built to warn the public, not to enforce, just for a different hazard. 🇩🇪 Hamburg Heavy Rain Map & Severity Index · Hamburg Contrast: Hamburg's rain index only nowcasts, no forecast; this bathing-water tool models forward to a red/green call.

May you swim? Three cities, three answers from the same kind of sensor

All three measure bacteria in urban water. What separates them is what the reading is allowed to do — post a warning, open a gate for the day, or file a report with a court for eighteen years running.

ProjectSinceStatusOutcomeEvidenceRun byCostWhat the reading does
Copenhagen Bathing Water Forecast & Overflow Warning SystemCopenhagen, 🇩🇰 2002 Live Succeeded Official City government, Utility or public operator not public Forecasts rather than measures after the fact: rainfall and sewer-overflow data estimate risk and raise a red flag before anyone gets in.
Seine Bathing-Water Sensing & Public Swimming ReturnParis, 🇫🇷 2025 Live Succeeded Official City government not public Decides the day. Sites open or close each morning on that morning's water-quality result, under health-authority control.
Pasig River: Court-Ordered Water Quality MonitoringManila, 🇵🇭 2008 Live Ongoing Peer-reviewed National government not public Reports to a court, indefinitely, and the river still fails — a court can compel measurement for decades; it cannot compel the sewers that would change the reading.

Explore the wider context

📟 A Reading Is Not a Decision📖 Air quality index (AQI)📖 District metering area (DMA)📖 Non-revenue water (NRW)
📎 Cite this project

1001 Smart Cities (2026). “Copenhagen Bathing Water Forecast & Overflow Warning System” — Copenhagen, Denmark. The Smart City Atlas. https://1001smartcities.org/projects/copenhagen-bathing-water-forecast/ (last verified 2026-10-14). Data: CC BY 4.0.

The underlying data is free to reuse with attribution — see the open data page.

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