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DWMP Strategic Context

Drainage and wastewater services are essential for a strong economy, safe society and a healthy environment. Our infrastructure, and the work we do to provide drainage and wastewater delivers an essential service for our customers, communities and businesses within our operating area.


Our Drainage and Wastewater Management Plan (DWMP) is a new long-term plan that sets out how we intend to maintain, extend and improve our systems to ensure they are robust and resilient to 2050 and beyond. It provides greater transparency, robustness and clarity for our future investment decisions.

Our Strategic Context sets out the process we’re using to develop our DWMP – including the challenges we face in our region, the Planning Objectives we will work to deliver, how it links to our other plans and with the plans of other organisations, and who we’ll be working with to develop our plan.


We serve around 4.6 million customers in Kent, Sussex, Hampshire and the Isle of Wight and protect a wealth of natural beauty – with over 84 bathing waters, 3,400 km of rivers, four Areas of Outstanding Natural Beauty (AONB), the South Downs and New Forest National Parks and numerous internationally designated ecological sites.

Across our region, we have 39,872 km of sewers and 3,420 pumping stations collecting wastewater from two million customers’ homes and businesses. Each day, more than 745 million litres of wastewater are carefully screened, filtered and treated at our 365 treatment works, meeting strict environmental standards before being returned to the environment.

A core focus of our wastewater service is to protect, restore and further improve these natural assets, while continuing to build operational resilience in the face of high population growth and increasingly extreme weather – among a raft of other pressures. The challenge is significant.

To respond to the challenge, we need to think and act differently – including working more closely with other organisations that have responsibilities for water management and protection of the environment. As part of our approach to developing our DWMP, we’ll be taking the opportunity to find new ways to work more collaboratively.

Level Description
Level 1 – Company Level The Level 1 plan covers the company’s whole operating region. It details its corporate strategy for drainage and wastewater management and its long-term investment planning to secure the outcomes and resilience for customers and the environment. The Level 1 plans brings together information from levels 2 and 3 planning to provide a strategic, long-term plan for drainage and wastewater resilience and associated investment over the next 25 years.
Level 2 – Strategic Planning Areas These plans are aligned to individual River Basin Districts (RBD) catchments. They look strategically across each of these individual catchments, so long-term drivers for change can be identified and holistic options considered at the catchment scale. They describe strategic issues and future risks across the geographical area, along with the strategy for investment to manage and reduce the risks to people, businesses and the environment for the future (short, medium and long term). This provides a strategic context for detailed assessments that take place at Level 3.
Level 3 – Wastewater Catchment / System Level Detailed plans for wastewater treatment works and the sewerage network system, including Drainage Area Plans (DAPs) and Drainage Strategy Frameworks (DSFs). These cover specific local geographical areas within each of the river basin district catchment. Level 3 plans investigate specific current or future local operational problems or issues to identify local solutions that align with the broader policies for the regional Level 1 plan and the strategic options set out in the Level 2 plans.

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

The key dates for the development of our DWMP 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 stakeholders on the catchment based DWMPs (Level 2)
Summer 2022 Public consultation on the regional DWMP
January 2023 Publish report on the public consultation
May 2023 Publish final DWMPs for Southern Water

We’ve scheduled a period of three months in the summer of 2022 for the final public consultation, three months to respond to the consultation and another 3 to 4 months to finalise our plan. This will allow our partners and customers to have a final say on our first DWMP before it is 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 in mid 2023 to inform PR24 business 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

Our DWMP will create strong links to these statutory and non-statutory plans, so our DWMP considers wider objectives and future needs. 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.

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.

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