The DWMP blog - Episode 1 The background

By the middle of 2022, water and sewerage companies in England and Wales must produce Drainage and Wastewater Management Plans (DWMPs) setting out long term plans for the development and maintenance of resilient drainage and wastewater systems.?

This is the first of a series of blogs discussing aspects of DWMPs and setting out how to improve their preparation and effectiveness.??

The process started because of UK Government concern over the lack of capacity and resilience to deal with increased urbanisation, more and denser housing and climate change.?The Government was concerned that, without long term planning, house building and associated economic development would be delayed.

Water UK (the body representing the water companies) established a programme in 2016 to provide guidance for these plans with a first draft in 2018 and a final version in 2019.?The companies then set out to deliver the first cycle of DWMPs.

The DWMP guidance totalled about a thousand pages of documentation and set many challenges for how to actually deliver DWMPs in practice.

This series of blogs will consider the questions that I found myself asking during this first cycle of DWMPs and how my thinking about the answers developed as I experienced different approaches.?This thinking was influenced and challenged by many people from many different organisations and I am grateful to all of them for their insights.?They are too numerous to name here, but you all know who you are, so thank you.?However, the ideas set out here (including the bad ones) are my own.

The guidance for DWMPs borrowed some ideas from the existing long-term water resources management planning process (WRMPs).?The aspects of this that were admired were; that it looked long term, that it was statutory and that there was a common approach across the country.?However, rather more of the WRMPs than these features was incorporated into the guidance for DWMPs with some resulting confusion.?This will be the topic of the next episode of the DWMP blog.

Setting the scope for DWMPs is key – what do we mean by the drainage and wastewater system??The guidance focussed on foul and combined sewers draining to wastewater treatment works and were intended to give a more integrated consideration of the sewerage system, the treatment works that it feeds and the water environment that it discharges to.?But did this integration happen in practice??What about integration with surface water management plans??

Setting a long-term plan requires knowing the targets that you are trying to achieve.?Those targets are themselves uncertain as they are subject to political and social pressure.?So how do we set the targets and how do we ensure that they balance what society wants with what society can afford?

The guidance set out to avoid creating “a cottage industry around modelling”, but how do you consider the future without a model??Is any model better than no model??How do you use the model efficiently to give you the answers that you need?

The implementation of DWMPs requires consideration of future, long-term, scenarios of changes in society, climate, technology and resources.?The pressures are not just the obvious ones of increasing population and rainfall intensity but also higher temperatures, drier summers and demographic and social changes.?All of these have significant uncertainty; so how do we plan for an uncertain future?

How do you develop a long-term plan for assets with a long or infinite life??Do you plan first for the short term and then build on this for the long-term needs, or do you plan for the long term and see how much you need in the short term?

Once we have delivered (in full or in part) the first cycle of DWMPs, how do we improve them, update them, adapt them to future changes??What is the roadmap for improving the approach?

The questions that episodes of the DWMP blogs cover are:

1. The background (This episode).
2. How does a DWMP differ from a WRMP?
3. What is the drainage and wastewater system?
4. Do we need models?
5. Targets; cost or value?
6. Future uncertainty – is it what? or when?
7. Choosing options – stepwise or optimise?
8. Plan forwards or backwards?
9. Minimising modelling effort?
10. Is up-to-date the same as recently updated?
11. Are we following the roadmap?
12. Are we planning for imaginary flooding?
13. How much flood risk is too much?
14. How much overflow discharge is too much?
15. How do we model environmental impact?
16. No detriment – or levelling sideways.
17. DWMPs and asset health.
18. The significance of rainfall.
19. Getting the message across.
20. Methodology for Cycle 2.
21. Did we overlook strategy?

I suggest that you read the episodes in order.?You can find them all here: (https://tinyurl.com/MartinOsborneArticles)

I can promise that it will all be in much less than a thousand pages and I hope that it will be thought provoking and useful.