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Drainage and wastewater management

Creating resilient wastewater catchments

We’re managing wastewater and drainage issues to ensure your local area is ready for the impact of climate change and population growth.

Our Water Resources Management Plan (WRMP)  exists to protect your future water supply. We’re now creating a detailed Drainage and Wastewater Management Plan (DWMP) to manage your wastewater more effectively.

Our Drainage and Wastewater Management Plan (DWMP)

All water companies in England and Wales are committed to preparing DWMPs for the first time.

We work in diverse catchments, each with varying population levels, development opportunities and drainage capabilities. Our DWMP needs to support the whole of our region to protect your community and the environment long term. That’s why our DWMP must be partnership-led.

Since early 2019, we’ve been mapping catchments and compiling data to develop our DWMP. In coming years, we’ll be discussing the information we hold about our region with our stakeholders and receiving their feedback and regional data. This is to ensure we’re making proactive decisions and prioritising areas with the biggest drainage and wastewater management issues.

Our first DWMP needs to be ready to for consultation in summer 2022. The final plan must be completed the following Spring ahead of the next price review. DWMP plans will then be reiterated every five years.

A picture of a group wearing fluorescent jackets on the edge of a river looking into the water

The DWMP framework

In 2018, Water UK collaborated with water companies across the UK, plus the Department for Environment, Food & Rural Affairs (Defra); the Welsh Government; Ofwat; the Environment Agency; Natural Resources Wales; the Consumer Council for Water; ADEPT; and Blueprint for Water, to create a DWMP framework all water companies can use.

We’re currently working through the following five stages:

  1. Scope and context: An overview of our drainage and wastewater region as well as the drivers and objectives that shape the DWMP
  2. Initial catchment screening: An overview of our region’s results from the industry-wide catchment vulnerability screening against 17 different risk indicators
  3. Catchment risk analysis: A more detailed assessment of our catchments that will help us understand the risks they face and identify opportunities for solutions
  4. Developing interventions: A list of solutions we and/or our partners have considered as well as their feasibility
  5. Programme update: An up-to-date, high-level view of our plan and where we are

Scope and context

In stage one of the process, we wanted to make sure our partners knew how to contribute to our DWMP.


To help us maximise the benefits of our DWMP, we led a collaborative process that included measures to meet our collective drainage and wastewater objectives while protecting the environment.

In winter 2019, we completed a consultation period for our proposed objectives and carefully considered the comments we received.

Based on this groundwork, the first version of our DWMP will focus on the impact of growth and climate change between 2025 and 2050.

We’ll update this DWMP every five years to make sure the scope of our work can evolve. In future, this may mean including a wider range of measures to prevent incidents like sewer flooding inside homes and river pollution.

Find out more about our national planning objectives now.


We’ll continue to engage with our partners throughout the process until the final version of our plan goes to our regulators as part of our next business plan in March 2023.

We’ll work on the following three levels of engagement and data:

  • Level 1 – the company-level strategy: A plan covering the whole of the Thames Water region, developed from the bottom up
  • Level 2 – our engagement level: Stakeholder communication at established forums, such as the 13 Thames Regional Flood and Coastal Committee (TRFCC) strategic partnership meetings and catchment partnership regular sessions
  • Level 3 – our planning unit: Our wastewater treatment catchments and associated drainage areas

Working through existing forums will help us to gather insights and priorities from a wide group of stakeholders in a way that supports their limited resources (impacted by COVID-19 in 2020).

Overall, this will help us to create a more collaborative and issue-driven DWMP.

Initial catchment screening

In the second stage of our DWMP process, we carried out Risk-Based Catchment Screening (RBCS).

This high-level, risk-based review covered all 382 of our drainage and wastewater catchments, checking for significant challenges and determining if they need more detailed assessment.

We measured the risks in each catchment against 17 indicators. These include flooding, pollution and Sewage Treatment Works quality compliance with permits. If we didn’t identify any unacceptable risks for a catchment, we removed it from the planning process.

In the future, we’ll update this screening process to reflect changing catchment risks whenever necessary.

Access our portal to view the results of our RBCS 2019 assessment.

Baseline Risk and Vulnerability Assessment (BRAVA)

In the third stage of our DWMP process, we carried out a detailed catchment-level analysis. We looked specifically at the vulnerability of the catchments we identified in the RBCS stage in a variety of scenarios.

We call this our Baseline Risk and Vulnerability Assessment (BRAVA).

During this process, we've analysed each drainage and wastewater catchment against the 17 indicators of our RBCS in more detail, considering future changes that could impact our plans over the next 25 years.

This will help us to understand wider resilience issues within each catchment as well as areas we need to prioritise in the next stage.

Access our portal to find out more about the results.

Developing interventions (optioneering)

In the fourth stage of our process, we’ll develop solutions and possible interventions for problems we’ve highlighted through our BRAVA.

We’d love to hear your ideas, including how they may fully or partially meet our objectives. We’ll collate and test all the ideas we receive before we decide which ones to move ahead.

We’re also open to forming new partnerships that will help us address not only our needs, but yours, too. By working together, we can make a wider contribution to local communities around our region.

More information

Please email us to find out more about our DWMP.

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