Why develop DWMPs?

Find out why we’re developing drainage and wastewater management plans (DWMPs) for our region – including the pressures our plans will help us address and the benefits we expect to achieve as a result.

Why are we developing DWMPs?

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

We serve around 4.6 million customers in Kent, Sussex, Hampshire and the Isle of Wight (IoW), and protect a wealth of natural beauty – with over 80 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.

A core focus of our wastewater service is to protect 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.

Our wastewater operations

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, 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.

During 2015–20, we invested over £400 million on our wastewater services including:

  • maintenance on sewers and wastewater pumping stations
  • replacing/refurbishing 100km of sewers based on our asset deterioration modelling and risk assessment
  • investing £268 million to reduce the number of blockages in our sewer network.


The pressures we face

There are very real external pressures that we have to prepare for now. These include:

Population growth

Population growth results in additional homes connecting into existing sewerage systems, and new towns being developed that require new infrastructure. We experienced the highest rate of population growth (5.3%) of all water companies between 2009 and 2013. This rate of growth has been increasing and is forecast to step up with a further 800,000 people forecast to be living in our area by 2040. In the short-term, we’re planning 20 infiltration reduction schemes, major growth schemes to support 100,000 new properties, rehabilitation of and 73km of sewers and rising mains.

Climate change

Climate change is affecting our weather patterns and the frequency and intensity of rainfall. For example, 2016 was the warmest year on record, and the third record warmest year in a row. In 2018, we faced a period of extreme cold then rapid temperature rise causing ice to melt – a process that caused many burst water mains and supply interruptions.

Heavy rainfall is on the increase, and we’ll see more weather extremes that will make preventing customers being affected by flooding or pollution a key challenge.

Urban development of housing, roads and infrastructure

Development is resulting in fewer green spaces and trees to absorb rainfall and reduce run-off.

Environmental protection

tightening environmental permits are driving future investment. The Water Framework Directive is the primary legislation that protects rivers and lakes, estuaries, coastal waters and groundwater, and determines what action needs to be taken to ensure all aquatic ecosystems meet ‘good status’ (or ‘good ecological potential’ for heavily-modified water bodies) by 2027.

Almost a quarter of our wastewater treatment works already have tight and challenging quality permits, so we’re under significant pressure to keep rivers, lakes, reservoirs and coasts healthy and clean. As a result, we’re already planning one of our largest ever environmental programmes.


Chemicals enter the drainage network from homes and business (including trade effluents and run-off from farms), as well as highways. Concern has been expressed about the potential for certain chemicals and pharmaceuticals that may be present in river water to disrupt hormone systems in both humans and wildlife. So we’re investigating and monitoring these chemicals as part of the UK Water Industry Research’s ongoing Chemical Investigations Programme.

Protecting public health

For example, the European Union Bathing Water Directive has two bacterial indicators (E. coli and intestinal enterococci) to measure the quality of the water. Bathing waters will be classified against these standards so people can make informed decisions about using the water for swimming and other leisure activities.

Plastics pollution

We’re facing a growing number of products that could have a significant impact on people and the environment if allowed to flow unchecked through the water cycle, including micro-plastics.

Carbon emissions

water industry operations require large amounts of energy for treating drinking water, processing wastewater, and pumping large volumes around an extensive network.

Greenhouse gas emissions from the operational side of the water industry are around 0.62% of UK emissions (BEIS and Water UK, 2019), so there is significant pressure to reduce carbon emissions from our wastewater systems and make them more efficient.

Ageing assets and infrastructure

Much of our sewer network is in over 50 years old. As a result, despite record investment, some public sewers are deteriorating and can collapse, block or suffer from infiltration by either rising levels of groundwater or flooding.

We realise the scale of the challenges we face. To respond to them, 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.

For more information about the challenges and drivers behind our, please read our DWMP Delivery Plan.


The benefits of DWMPs

Our vision for the future is about transforming the role of water in our daily lives. It is about providing a resilient future for water in the South East by transforming the way we work and creating new solutions to meet the challenges ahead.

We’re committing to being bold and innovative so we can meet our customers’ expectations, keep water services affordable and, at the same time, improve our precious environment, support tourism, economic growth and invest in the future of our children and grandchildren.

The DWMP will give us valuable data about drainage and flooding across our region and help us identify where we need additional information to support our future plans. It will also help us identify where future investment in our wastewater infrastructure, people and systems is needed – taking into account economic, social and environmental factors.

In terms of the environment, the DWMP will provide a forum for us to engage with partners concerned with protecting the environment through the use of natural capital accounting – which we’ll be piloting in three catchments over the next five years – to appraise the options available.

Meanwhile, linking our DWMPs to the performance goals we aim to achieve by 2040, we can drive co-ordinated, timely and sustainable investment decisions across our business that support our objectives.

We expect our DWMPs to achieve the following key benefits:


  • Providing a comprehensive integration with existing risk and resilience systems and from PR24 forming the basis of future business-as-usual wastewater asset and investment planning activities.
  • Assessing where (largely drainage) infrastructure managed by other stakeholders may impose additional risks to drainage and wastewater services.
  • Developing planning scenarios for future states based on the challenges and drivers for change – such as growth, climate change and technology – and the long-term drainage and wastewater capacity of our systems.

Systems thinking

  • Establishing a systematic understanding of our wastewater services and current system risks across our operational region and the wider South East.
  • Considering and assessing long-term impacts and risks to – and from – drainage and wastewater systems.
  • Developing a wider understanding of the interdependencies between infrastructure systems, impacts arising from loss of critical infrastructure and cascade failures.

Value engineering

  • Identifying options that offer best value to customers and the environment – ensuring robust, resilient and sustainable drainage and wastewater services in the long-term.
  • Delivering alternative, catchment-based solutions that tackle the issues at source, rather than at end-of-pipe.


  • Supporting economic growth and community resilience, as well as co-creating plans and solutions that are aligned with other organisations' planned investment in water quality, flooding and drainage.
  • Facilitating partnership-working with spefific regard to plans made by other Risk Management Authorities for sustainable drainage, flooding and pollution management.
  • Strengthening our structured and auditable approach to identifying and developing robust investment plans that meet stakeholders' requirements and deliver best value for customers.

Our DWMPs will be key in helping us achieve these benefits, which will be secured by working with others, adopting systems thinking, building resilience and delivering best value water and environmental engineering solutions.

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