Published Overflow Data
Overflow Data
We are committed to providing accurate information about the performance of our sewer network as part of our approach to improving water quality in Scotland.
In our Improving Urban Waters Routemap, published in December 2021, we said we would increase reporting of overflow data from monitored overflows over time:
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By December 2022 publish data annually for monitored overflows where data is already reported to SEPA, identifying the main reason for the overflow event where possible
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By December 2023, publish data annually for all other monitored overflows
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By December 2024, publish near real-time data for all monitored overflows
What has been published?
We have made available the following data:
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Overflow data included within our annual regulatory reporting to SEPA covering the period 2019-2023
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Overflow data from all other monitored overflows covering 2022 & 2023 only where data has been verified
The overflows covered are:
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Combined Sewer Overflow (CSO) which stop the system from becoming overwhelmed during heavy rainfall
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Settled Storm Sewage Overflow (SSSO), a form of CSO that provides a level of treatment or settlement before discharge
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Emergency Overflow (EO) which should only operate in the event of sewer system failure and should not operate in response to rainfall.
Overflowdata in the regulatory return is reported annually to SEPA in line with specific requirements set out within our licenses.
We first published this information on our website at Overflow Data in December 2022 (2017 to 2021 data). It was updated in 2023 and again in 2024 to show data for the previous five year period. Updates will be published annually going forward.
Our commitment to making more data available is one of the commitments in our Improving Urban Waters Routemap.
As a result, verified data for other monitored overflows, where regulatory reporting is not required, was first published in December 2023 (2022 data). This has now been updated to include 2023 data and updates will be published annually going forward.
As we continue our review and verification processes, we will look to publish data for further monitored overflows where available in the future.
The information is available in searchable format by clicking on the blue box at the top of the page and selecting 'download'.
Discharge data is supported by additional information, including metadata, user guidance, postcode, local authority area, and receiving water.
Published Overflow Data
Download the Scottish Water Reported Overflow Event Data to SEPA 2019-2023 & Summary
DownloadOther Overflow Event Data
Download the Scottish Water data for other monitored overflows in 2022 & 2023 not reported to SEPA
DownloadOverflow Event Data
Download the Scottish Water Reported Overflow Event Data to SEPA 2019-2023 & Summary.
Download here
Overflow Monitor
Scottish Water committed to installing 1000 new monitors over 2024
Additional information
Please note that this data covers only monitored overflows where data has been quality assured.
Where Event Duration Monitoring (EDM) is a regulatory requirement, we are required to monitor the frequency and duration of releases from overflows. The published overflow data is based on available EDM data.
It’s important to note that the data received from our EDM monitors may not always be accurate. EDM data doesn’t confirm discharges, it only indicates them. For example, the monitors can be very sensitive and can be set off by vegetation movement. Published data is based on a review of the available data which may vary between monitoring locations.
Reasons for overflow events are not available for historic events because Scottish Water has not been required to collect or report this information. Scottish Water aims to develop approaches to help identify reasons for overflow events and this will become part of future releases of information.
Some parts of the system are operated on our behalf by PFI operators. Where identified as the responsible person for the asset within the discharge license, these operators submit flow and event returns directly to SEPA.
Scottish Water does not publish information other operators report to SEPA. However, as PFI assets return to Scottish Water ownership at the end of PFI contracts, we will then include overflow data from these in our future annual returns to SEPA and this will subsequently be published.
Any grid references within the data set relate to the asset location/monitoring point and not the receiving water.
Find out more about Scotland’s sewers and our improvement plans
