This statement provides information about statistics concerning aspects of water in Scotland and England that were presented in July 2025 in:
- A letter and accompanying table sent on 24 July from Steve Reed MP – the Secretary of State for Environment, Food and Rural Affairs at the time – to Stephen Flynn MP (published on X on 25 July). The Secretary of State sent this letter to Stephen Flynn in support of statements made in the House of Commons on 21 July , which compared Scotland and England in terms of water pollution, and in the context of nationalised and privatised water company ownership models.
- The Independent Water Commission (IWC)’s final report (published on 21 July). This report contains water quality statistics that were directly relevant to the debate, which were flagged in a 22 July letter to the Secretary of State from Gillian Martin MSP, Cabinet Secretary for Climate Action and Energy.
This statement focuses on statistics relating to the following aspects of water:
- Sewerage pollution incidents
- Storm overflow monitoring
- Household water usage
- Water leakage (proportion of supply)
- Water leakage (litres)
- Water meter coverage
- Surface water quality
- Bathing water quality
Sewerage pollution incidents
Statement: “There were 35.8 incidents per 10,000km of sewer in Scotland versus 35.4 incidents per 10,000km of sewer in England and Wales reported in 2023-24.” [24 July letter]
OSR view
While the 24 July letter did not provide a source for this statistic, we were able to identify how the figures for Scotland and for England and Wales were produced. However, several caveats limit the quality of this statistic, particularly for comparing between countries. The substantial caveats – together with the small difference between the estimates – led to our view that this statistic is not of a sufficient quality to use as a basis for robust conclusions. We conclude that there is not suitable evidence to allow for a meaningful comparison of the number of sewerage pollution incidents in Scotland and in England and Wales in 2023-24.
The statistic above was presented in the 24 July letter, although the letter did not provide a source for the statistic. Defra informed us that the figure for England and Wales was taken from Ofwat’s Water company performance report 2023-24 (p24), and the figure for Scotland was calculated using figures from Scottish Water’s 2023-24 report (p3 and p28).
While we were able to identify and recalculate the sewerage pollution incidents statistic from these sources, there are several caveats to consider when comparing countries on this basis. We summarise these caveats below:
- The IWC report did not include comparisons of pollution incidents because of challenges in comparing nations due to differences in monitoring and reporting such incidents. As indicated in the storm overflow monitoring statistic presented in the 24 July letter (see next section), England and Scotland differ substantially in terms of the proportion of monitoring coverage. An Environmental Standards Scotland (ESS) report also highlights that the figures for England and Wales are reported by calendar year, while figures for Scotland are presented by financial year. We also identified that the sewer length data used in the calculations were from 2018 for England (table 5.2.9.), and from the end of the 2023-24 financial year for Scotland (table D6).
- The statistic presents a figure for England and Wales combined, although England and Wales have different models of water company ownership. As the 24 July letter was produced in the context of nationalised and privatised water company ownership models – comparing Scotland and England, respectively – it could be viewed as inappropriate to include data for Wales in this statistic. A figure for England could have been calculated from the individual water company data reports published by the Environment Agency. However, there are other difficulties to consider in distinguishing England and Wales in this way, as companies in Wales serve small parts of England, and companies in England serve small parts of Wales.
- The figure for England and Wales appears to only include incidents from sewerage assets, and not from water supply assets. However, the figure for Scotland appears to include incidents from sewerage and water supply assets. As the Scottish Water report (p28) suggests that not all (‘most’) incidents occurred in the sewerage assets, it is possible that the figure for Scotland is an overestimate. The ESS report highlights the need for more transparent and detailed data for Scotland concerning these incidents, which would enable incidents from sewerage and water supply assets to be considered separately.
Storm overflow monitoring
Statement: “Storm overflow monitoring coverage in Scotland was 28% in 2024, while England has 100% coverage.” [24 July letter]
OSR view
The finding that England has 100% coverage, and a much higher proportion of storm overflow monitoring than Scotland, is supported. However, the extent of the difference is difficult to determine, as the figure for Scotland is approximate.
A 2023 Defra and Environment Agency press release is provided as the source for the figure for England and is also referenced in the IWC report to support the same figure. While the letter details the sources and the way in which the figure for Scotland was calculated, a 2024 ESS report notes that the figure is difficult to determine accurately. As such, the figure for Scotland should be clearly framed as being approximate.
As acknowledged in the 2024 ESS report, England and Scotland have different policies relating to storm overflow monitoring. As such, while the exact proportion of overflows in Scotland that are monitored is unclear, the finding that a higher proportion of overflows are monitored in England than Scotland is highly unlikely to change.
Household water usage
Statement: “Average household water use is also significantly higher in Scotland (178 litres per person per day), compared to England (137 litres in England).” [24 July letter]
OSR view
This statistic appears to be correct, although the source indicates that the figure for England is a combined average for England and Wales. While we identified a discrepancy between sources for the figure for England, there appears to be support for the figure presented in the 24 July letter.
A Scottish Water strategy article is provided as the source for this statistic, although this article does not provide the origin of the figures. The same article is provided as the reference for the Scottish figure in the IWC report. As stated in the article, the figure for England reflects a combined average for England and Wales (this figure is also presented on p295 of the IWC report). The figures for England and Wales are presented separately on p298 of the IWC’s report, and the figure for England is taken from Ofwat’s water company performance report 2023-24 (p16). However, the figure for England on p298 indicates that water usage is 140 litres per person per day, while the Ofwat source indicates that English companies had a one-year average usage of 137 litres per person per day. The reason for this discrepancy is unclear, although the Ofwat source supports the figure for England presented in the 24 July letter.
Water leakage (proportion of supply)
Statement: “25% of total water supplied in Scotland is lost to leakage compared to 19% in England (2023-24).” [24 July letter]
OSR view
The sources for these figures were accurately presented. While an alternative figure for England is presented in the IWC’s report, the Environment Agency figure presented in the letter appears to be more comparable to the figure for Scotland.
The IWC report presents an alternative figure for England (23%, p298), although this represents the percentage of water produced that is lost or unbilled (‘non-revenue water’). The IWC report notes that non-revenue water is distinct from the metric used for Scotland. The IWC figure also relates to a different period (2022-23), and the source is not freely accessible.
Water leakage (litres)
Statement: “Leakage, litres of water leaked per person per day (2023/24) – England 49, Scotland 84” [24 July letter]
Statement: “Leakage, litres of water leaked per household per day (2023/24) – England 118, Scotland 183” [24 July letter]
OSR view
The figures for England in these statistics actually relate to England and Wales, which is noted under the 24 July letter’s accompanying table but not in the table itself.
There are inconsistencies with how these statistics are presented in terms of relating to England alone, or England and Wales – the table’s column refers to ‘England’, while the footnotes refer to ‘data for England and Wales’.
Using the sources provided in the 24 July letter, we were able to recalculate both of the statistics (using the combined figure for England and Wales), except for the per person daily water leakage in Scotland, as the source for Scotland’s population size was not clear. As each data source presented the figures for England and Wales separately, we were able to recalculate the leakage figure for England only and found that the pattern of findings did not change substantially.
Water meter coverage
Statement: “Water meter coverage, % of all households (2024) – England 60%, Scotland 3%” [24 July letter]
OSR view
While the broad pattern of findings appears to be supported – there is higher water meter coverage of households in England than in Scotland – both figures are likely to be approximate.
The figure for England is taken from research and analysis undertaken by the Environment Agency, which states that the figure is approximate (‘around 60%’). The figure for Scotland is calculated from a Scottish Water article. The article states that Scottish Water provides unmetered water supply to 97% of households in Scotland, therefore suggesting that the remaining 3% of households have water meter coverage. However, the article states that the number of households in Scotland on private water supply or supplied through a business (73,000) is approximate.
Surface water quality
Statement: “Surface water quality (achieving good or excellent status) – Scotland 66%, England 16%” [IWC report]
Statement: “Water bodies at poor or bad status – Scotland 14%, England 20%” [IWC report]
Statement: “Surface water quality achieving bad status – Scotland 3%, England 3%” [IWC report]
OSR view
These statistics indicate that a higher proportion of surface water is classified as good or excellent in Scotland than in England. The countries are more similar in terms of the proportion of surface water that is classified as poor or bad. While we identified differences between how the figures for England and Scotland were produced, the patterns of the findings are unlikely to be substantially affected.
These statistics were presented in the IWC report (p125 and p299). The sources for the figures for England were accredited official statistics. Using the sources provided for Scotland, we were able to repeat the calculations. However, we note that the Scottish Environment Protection Agency (SEPA) source provides figures separately for surface water and groundwater, while the IWC report combines these figures. As the figures for England only appear to relate to surface water, we are unclear why the IWC has included groundwater in the calculation of the figure for Scotland. However, we repeated the calculations for surface water alone, and found that the results do not change substantially.
The House of Commons Library published a research briefing concerning water quality in January 2025, and this briefing draws on more recent data on surface water and groundwater in Scotland (2023). We focus on the IWC report as it compares the countries across a more similar period using the latest data for England (England 2019, Scotland 2020). However, the more recent data for Scotland indicate a similar pattern of results.
The IWC report highlights factors that could lead to differences in water quality between Scotland and England (and other countries). For example, Scotland has a considerably lower population density than England. This is important as it emphasises that water quality is affected by several factors and cannot be attributed to just one (for example, water pollution incidences).
Bathing water quality
Statement: “Bathing water quality (good or excellent) – Scotland 87%, England 85%” [IWC report]
OSR view
We view this statistic to be appropriate – specifically, that Scotland and England have a broadly comparable proportion of bathing water sites that meet good or excellent standards.
This statistic was presented in the IWC report (p299), and the sources for the figures were accurately presented.
As stated above, several factors contribute to water quality status (for example, population density), so attributing water quality to any one specific factor should be avoided.
Related
Letter from Professor Dame Carol Propper to Seamus Logan: MP statements on water quality