Automating DWMP Workflows to Reduce CSO Spills

Automated Drainage and Wastewater Management Plan (DWMP) workflows help water companies turn established modelling processes into repeatable, scalable analysis. They can automate model maintenance, calibration, scenario preparation, risk assessment and solution development across  multiple time horizons. By connecting existing models, data and water modelling processes into a controlled workflow, water companies can build a stronger evidence base for CSO investment decisions while reducing the repetitive manual work required to produce it.

Drainage and Wastewater Management Plans are now a statutory planning requirement for sewerage undertakers in England and Wales. The latest government guidance requires companies to prepare, publish and maintain plans that support resilient drainage and wastewater services and align with related flood-risk and drainage strategies.

Why are DWMP workflows important for CSO spill reduction?

Reducing CSO spills requires more than identifying where a network is currently under pressure. Water companies need reliable evidence to understand current performance, predict how it may change over time and determine which interventions will deliver the greatest and most resilient benefits under different future scenarios.

DWMP workflows provide a structured way to build this evidence at scale. By embedding agreed modelling methods, quality checks and standards into automated processes, they can ensure model updates, calibration, option appraisal and solution development are applied consistently across catchments.  

Automation also increases the scale and speed of analysis. Tasks that would otherwise require significant manual effort can be applied consistently across large numbers of models and CSOs, allowing teams to assess more locations, investigate problems in greater depth and evaluate a wider range of potential interventions within DWMP programme timescales.

Most importantly, workflows enable a more systematic approach to solution development and investment planning. Rather than developing and assessing interventions individually, teams can explore combinations of solutions, test them across different scenarios and compare their performance against cost, carbon and wider environmental or social objectives. 

This is particularly important because interventions interact across a network. An improvement at one location may reduce spills locally while increasing hydraulic pressure elsewhere. Catchment-wide modelling allows these interactions to be understood and helps avoid developing solutions in isolation. 

Testing interventions across multiple scenarios and planning horizons also allows their robustness to be assessed. Workflows can identify no-regrets solutions that continue to provide benefits under a range of possible futures, while highlighting where predicted outcomes are particularly sensitive to uncertainty. 

Ultimately, automated DWMP workflows help move CSO modelling from a largely manual exercise into a repeatable evidence-generation process. This gives water companies greater capacity to understand their networks, compare investment options and identify interventions capable of delivering sustained improvements in CSO performance.  

Which DWMP activities can be automated?

Automation is particularly effective for repeatable, rules-based activities such as the following DWMP activities:

How does automation improve model consistency?

Automation improves consistency by applying the same approved rules, templates and checks across every model included in a programme. Manual updates can vary between individuals, consultancies and catchments. Differences in naming conventions, data structures, local procedures and interpretation can make later analysis difficult to compare or repeat. A controlled workflow provides a common method for gathering data, applying changes, recording assumptions and producing updated networks and simulations.

For water companies managing hundreds of models, this provides a scalable way to apply agreed processes across all models without repeatedly recreating or manually managing the same approach for each catchment. Engineering review remains central. Modellers still need to confirm that source data are suitable, local assumptions are valid and updated models behave as expected. Automation supports the procedural elements of the process; experienced engineers retain responsibility for technical judgement and sign-off.

Where does calibration fit?

Calibration is an optimisation task that can be accelerated through automated methods. For CSO assessment, models may require further refinement to reproduce seasonal variation and annual spill frequencies with sufficient confidence. Runoff response, rainfall-dependent infiltration and groundwater infiltration can all influence predicted spill behaviour, particularly where historic models were verified against short monitoring periods.

Automated calibration can test parameter combinations across several monitors, events and time periods. Engineers define acceptable parameter ranges, review diagnostic outputs and decide whether the model is fit for purpose. The workflow therefore accelerates the computationally intensive part of calibration without replacing engineering judgement or verification.

How can automated DWMP workflows support better CSO decisions?

Automation enables teams to move beyond assessing individual interventions and systematically explore a much wider range of solutions and investment strategies catchment-wide. Rather than repeatedly running models manually for each option, structured workflows can test different combinations of interventions across multiple scenarios and identify how they interact across the wider network. This is important because an intervention that reduces spills at one location may increase hydraulic pressure elsewhere.  

Teams can assess combinations of:

• Pipe and pump upgrades
• Online or offline storage
• Flow controls and real-time control
• SuDS and surface water separation
• Strategic diversions
• Operational changes

Optimisation can then identify combinations that provide strong performance against defined objectives and constraints, helping teams understand trade-offs between cost, CSO spill reduction and wider outcomes. The same workflow can be used for prioritisation studies, identifying where intervention is likely to deliver the greatest benefit, and adaptive pathway planning, assessing how different investment strategies perform as future conditions change.

This provides a more comprehensive evidence base for deciding where to invest, which interventions to pursue and how investment should be phased over time.

Building a scalable and auditable DWMP process

Automating repeatable DWMP activities gives modelling teams a stronger foundation for reducing CSO spills. Consistent model updates, scenario preparation and results processing improve traceability, reduce avoidable rework and support clearer comparisons between intervention options.

STRIDE uses HEEDS and its Water API to connect hydraulic models, GIS data, spreadsheets, scripts and internal tools within a configurable workflow. Engineers retain control of the assumptions, constraints and technical decisions, while HEEDS manages repeatable processing and records how outputs were produced.

This approach helps water companies maintain models across multiple catchments, respond to changing planning assumptions and develop more robust evidence for CSO spill reduction, investment planning and regulatory assurance.

Learn how to automate DWMP workflows and reduce CSO spills in every catchment. Download A Water Modeller’s Guide to Reducing CSO Spills now.