Additional Resources - to July 2025
Ecological studies
Important findings from an analysis of national macroinvertebrate trends for England revealed that the richness of invertebrate communities in rivers increased between 1991 and 2019. Also see a report on evidence of biological recovery from gross pollution in English and Welsh rivers.
A study carried out on data collected between 1989 to 2018 for England found significant improvement in freshwater invertebrate biodiversity in all types of rivers.
Despite the 2023 State of Nature report on the UK’s current biodiversity showing widespread declines, the specific data included for water quality was more encouraging. For example, freshwater insect groups initially declined before recovering; and between 1993 and 2022, numbers of bottom-dwelling fish for Wales, England and Northern Ireland Celtic Seas increased.
A report on the potential drivers of changing ecological conditions in rivers shows that ammonia, biochemical oxygen demand and phosphate concentrations have declined widely since 1990. Biodiversity increased since 1990, although there is some evidence that trends have slowed in recent years.
Overall, these studies show a significant improvement in river water quality leading to a greater abundance and diversity of wildlife in rivers in England since privatisation of the water industry.
Important findings from an analysis of national macroinvertebrate trends for England revealed that the richness of invertebrate communities in rivers increased between 1991 and 2019. Also see a report on evidence of biological recovery from gross pollution in English and Welsh rivers.
A study carried out on data collected between 1989 to 2018 for England found significant improvement in freshwater invertebrate biodiversity in all types of rivers.
Despite the 2023 State of Nature report on the UK’s current biodiversity showing widespread declines, the specific data included for water quality was more encouraging. For example, freshwater insect groups initially declined before recovering; and between 1993 and 2022, numbers of bottom-dwelling fish for Wales, England and Northern Ireland Celtic Seas increased.
A report on the potential drivers of changing ecological conditions in rivers shows that ammonia, biochemical oxygen demand and phosphate concentrations have declined widely since 1990. Biodiversity increased since 1990, although there is some evidence that trends have slowed in recent years.
Overall, these studies show a significant improvement in river water quality leading to a greater abundance and diversity of wildlife in rivers in England since privatisation of the water industry.
- Missing spills data: Comparison of Storm Overflow operational data across water companies:
Recap of development situation re surface water separation
All new development should have separate drainage systems for foul and surface water no matter how small, although there are lower standards that can be used if it is not practical to provide a truly separate system. WW tries to rebuff any attempts to connect rain to sewers that carry foul sewage, regardless of how hard it is to dispose of the rainfall elsewhere. We may find that some developers make a legal appeal because of this – we will see, and in that case, the principles and law will be tested.
New building regs were issued in 1965 that referred to sewers and drains. They did not contain specific requirements for separate drainage, however. Despite this, it was during the 60’s that developers and planners recognised the value of separate sewer systems, and these started to be constructed.
The ‘right to connect’ remains in the Water Industry Act, and that is a problem. Introducing Schedule 3 of the Flood and Water Management Act would be a big step towards solving it. Schedule 3 would provide a framework for the widespread adoption of SuDS (sustainable drainage systems) and gives local authorities the role of sustainable drainage approval body (SAB), with responsibility for checking compliance and approving their use. We are hopeful that it will be adopted soon.
Here are more current blockers to good rainwater management at homeowner level:
All new development should have separate drainage systems for foul and surface water no matter how small, although there are lower standards that can be used if it is not practical to provide a truly separate system. WW tries to rebuff any attempts to connect rain to sewers that carry foul sewage, regardless of how hard it is to dispose of the rainfall elsewhere. We may find that some developers make a legal appeal because of this – we will see, and in that case, the principles and law will be tested.
New building regs were issued in 1965 that referred to sewers and drains. They did not contain specific requirements for separate drainage, however. Despite this, it was during the 60’s that developers and planners recognised the value of separate sewer systems, and these started to be constructed.
The ‘right to connect’ remains in the Water Industry Act, and that is a problem. Introducing Schedule 3 of the Flood and Water Management Act would be a big step towards solving it. Schedule 3 would provide a framework for the widespread adoption of SuDS (sustainable drainage systems) and gives local authorities the role of sustainable drainage approval body (SAB), with responsibility for checking compliance and approving their use. We are hopeful that it will be adopted soon.
Here are more current blockers to good rainwater management at homeowner level:
- Powers for water companies to construct property-level solutions do not exist (e.g. we can only persuade homeowners to divert their roof rainwater away from the foul sewer even though this is a fundamental part of the storm overflow problem). We are currently seeking legal opinion to see if we have more powers to disconnect rain from the public sewer and direct the rain to private soakaways etc.
- Powers for water companies to discharge separated rainwater into watercourses do not exist.
- No Govnt incentives exist (unlike loft/wall insulation or electrical charging points).
- It’s not financially worthwhile for property owners to do it themselves (there is a small water bill discount available: Rainwater drainage allowance | Wessex Water )
- Separation leads to progressive not rapid improvements and water industry regulation/planning only works within 5-year blocks.
- Skillsets for the required building AND gardening work are not well established.
Andy Mears' Dec23 note - infiltration of groundwater into the foul system:
“I’ve listed out the SOs in West Dorset that are linked with groundwater inflow, or a combination of groundwater and direct rainfall. Our Matt Kettle provided notes on the infiltration work we’ve done upstream of each with some comments, as per the table below. Matt has presented at a series of Wessex Area Groundwater Prepared Roadshows recently, spearheaded by EA. These were aimed at residents in flood-prone areas. The survey and sealing figures provided below cover our most recent programmes. For some SOs, we have carried out previous survey and sealing works, some very extensively.
In areas where we suspect infiltration is a problem, we typically CCTV the sewers to try to locate the points of water ingress, then carry out sealing works. It can be hard to achieve the former however, because it is no use looking when the groundwater table is low, and if the GWT is too high, you still can’t spot the points of ingress because the sewers are simply full of water. You need to get your timing for the survey just right. In the table below:
“I’ve listed out the SOs in West Dorset that are linked with groundwater inflow, or a combination of groundwater and direct rainfall. Our Matt Kettle provided notes on the infiltration work we’ve done upstream of each with some comments, as per the table below. Matt has presented at a series of Wessex Area Groundwater Prepared Roadshows recently, spearheaded by EA. These were aimed at residents in flood-prone areas. The survey and sealing figures provided below cover our most recent programmes. For some SOs, we have carried out previous survey and sealing works, some very extensively.
In areas where we suspect infiltration is a problem, we typically CCTV the sewers to try to locate the points of water ingress, then carry out sealing works. It can be hard to achieve the former however, because it is no use looking when the groundwater table is low, and if the GWT is too high, you still can’t spot the points of ingress because the sewers are simply full of water. You need to get your timing for the survey just right. In the table below:
- CCTV meterage will include places where we’ve surveyed the same sewer length multiple times, so some catchments have quite high numbers because of this.
- In the same vein, where we haven’t had many problems in the past, some catchments haven’t really been looked at, so may only have low totals.
- For sewer rehabilitation meterage, there is only a small amount of double counting, e.g. where we did joint sealing in the noughties, and have since relined with Cured In Place Pipelining.
Note on bills from Andy Mears:
Whilst we have consistently pressed for higher levels of investment, Ofwat has historically prioritised bill reduction. The first graph below shows bills and inflation over the last 15 years.
The second chart shows how projected bill increases look based on our Final Determination, with historic figures adjusted up for inflation:
Whilst we have consistently pressed for higher levels of investment, Ofwat has historically prioritised bill reduction. The first graph below shows bills and inflation over the last 15 years.
The second chart shows how projected bill increases look based on our Final Determination, with historic figures adjusted up for inflation:
