Developing our DWMPs

Find out what process we’re using to develop our Drainage and Wastewater Management Plans (DWMPs) – including the timetable, how they link to our other plans and who we’ll be working with.

Our process

The process we’re following to develop our DWMPs is:

Step Name Description
1 Strategic context The strategic context defines the objective of the DWMP, the area that the plan covers and the planning objectives against which current and future performance is to be measured at a company and local planning level.
2 Risk based catchment screening Risk based catchment screening (RBCS) is designed to focus effort where there is evidence of flooding, pollution issues or other risks that may require action.
3 Baseline risk and vulnerability assessment The baseline risk and vulnerability assessment establishes the current position of issues in the drainage and sewer catchments, and assesses the potential impacts of future changes. It will also assess the resilience of the systems within the catchments.
4 Problem characterisation The problem characterisation identifies the nature and complexity of the interventions required and assigns the catchments to different levels of options development and appraisal.
5 Options development and appraisal The options development and appraisal develops a long list of generic options that could be considered to address the problems within the catchments. Appraisal of these options will lead to feasible options for future funding and implementation.
6 Programme appraisal The programme appraisal stage will define preferred options based on ‘best value’ and incorporating ecosystem services assessments / natural capital approaches, and develop a prioritised list of interventions and timetable.
7 Final DWMP programme The final DWMP is then produced, after external consultation, with a proposed investment programme, to inform our formal Business Plan development and submission to Ofwat to make the case for funding.

The final DWMP programme is then fed into the development of our Business Plan for the next price review period (PR24).

Risk based catchment screening

Risk based catchment screening (RBCS) is a process completed at the outset of developing a DWMP. It’s used to identify where a sewer catchment has a current and/or potential risk or vulnerability, so effort to can be focused on understanding the risk and why it’s likely to occur. Find out more about RBCS:


Risk based catchment screening

Planning objectives

The Water UK guidance sets out the need to establish planning objectives for a long-term planning horizon. These will be developed during the 'strategic context' stage. Find out more about planning objectives:


Planning objectives

Our timetable

The water-sector regulator, Ofwat, has set a timetable for delivering the first round of DWMPs. Though challenging, the timetable is necessary so our DWMPs can be used in the development of our business plan for the next price review (PR24).

The timetable is also driven by the need to inform the National Infrastructure Commission’s second National Infrastructure Assessment (NIA) into the state of the water industry’s infrastructure, due for publication in 2023.

The key dates for the development of our DWMPs are:

Timeline Activity
April 2020 Establish DWMP programme for the current funding period (2020–25), and commence work on developing the plans
June 2020 Update the Risk Based Catchment Screening (RBCS) for 2020
June – November 2020 Working with partner organisations to develop the strategic context, planning objectives and baseline risk and vulnerability assessment (BRAVA)
December 2020 Submission of BRAVA to Water UK
January – August 2021 Working with partners on options development and appraisal
Autumn 2021 Start early consultation with customers on the catchment based DWMPs (Level 2)
Summer 2022 Public consultation on the regional DWMP
January 2023 Publish final DWMPs for Southern Water
Our delivery schedule

We’ve considered the activities, sequence and resource requirements in detail. Based on this, we’ve developed an indicative delivery schedule for the delivery of the first round of DWMPs – shown in the Gantt chart below. We consider this realistic and achievable and it meets Ofwat’s timetable:

DWMP High Level Delivery Programme

The timetable for the delivery of the first round of DWMPs is a significant challenge. We understand what is involved and our detailed programme has considered how we will deliver the DWMPs. We’ll work hard to provide a good first set of DWMPs for our region to support our work with partner organisations, customers and our business plan for the next price review (investment) period for 2025 – 2030 (known as PR24).


Giving our partners and customers a say

We’ve scheduled a period of three months for the final public consultation and three months to respond to the consultation and finalise our plan. This will allow our partners and customers to have a final say on our first DWMPs before they’re published, as well as providing an ongoing mechanism for them to continue to have a say in our planning and investment decisions during implementation.

We’ll complete the first round of drainage and wastewater planning for our operating region by the end of January 2023. These final plans will be available in early 2023 to inform PR24 business plans.


Links to other plans

Several other plans will inform our DWMP – including plans from other organisations with responsibilities for drainage, water management and protection of the environment, including:

  • River Basin Management Plans (RBMPs)
  • Flood Risk Management Plans (FRMPs)
  • Local Flood Risk Management Strategies
  • Surface Water Management Plans
  • Local Plans (for future development and social change)
  • Water Resource Management Plan (WRMP) and Drought Plan

We will create strong links to these statutory and non-statutory plans, so our DWMPs consider wider objectives and future needs, and our decision making and timing of delivery is co-ordinated where possible, especially where we can work in partnership to jointly fund and deliver schemes.

In addition, our DWMPS will be supported by the key programmes within our Business Plan for 2020–2025:

  • Target 100 – Reducing average daily consumption to 100 litres per person.
  • Catchment First – Ensuring catchments are at the heart of decision making and delivery
  • Networks 2030 – Creating a more resilient supply network for future generations.
  • Resource Hubs – Transforming wastewater treatment works into community assets.
  • Sustainable Drainage 2030 – Creating capacity across the sewer network.

Our DWMP will also demonstrate where proposed activities may have a significant impact on other plans – for example, nutrient management plans and diffuse water pollution plans.


Find out more

For more information about the context of our DWMPs and our approach to delivering them, please read our DWMP Delivery Plan:

DWMP Delivery Plan

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