Grand Union Canal – Modelling

Location: Grand Union Canal                                                                                                                               Client: Affinity Water, Severn Trent Water, Canal and River Trust

Challenge

Water companies in England and Wales are currently investigating a wide range of potential ways to address the long-term challenge of providing resilient, sustainable sources of potable water in the face of the challenges of climate change, population growth and the need to reduce unsustainable abstractions. One of these Strategic Resource Options (SROs) under consideration is to use the Grand Union Canal to transfer treated effluent from Birmingham to the Affinity Water central supply area which forms a ring around the west and north of London.

The project is being developed collaboratively by Affinity Water, Severn Trent Water and the Canal and River Trust. JBA Consulting is commissioned, through the Affinity Water Professional and Technical Services framework, to undertake hydrological, hydraulic and water quality modelling of the transfer, along with hydrometric and topographic surveys of the canal and connected watercourses. Here, Technical Director Paul Eccleston introduces the approach taken to modelling this complex scheme.

Solution

The concept of using the Grand Union Canal to transfer water from Birmingham to Hertfordshire has been mooted for many years, so it was very exciting to be commissioned by Affinity Water to carry out the water resources, hydraulic and water quality modelling to assess this scheme. Depending upon the route selected, there are up to three summits over which water will need to be lifted, around 100 locks to be by-passed by pumping or by-weirs and channels, and inter-connections with sensitive rivers.

Grand Union Canal Modelling
Schematic showing flow pathways within a canal system. © JBA Consulting

The sources of flow into the canal are being modelled using hydrological (rainfall-runoff) models and water resource modelling software Aquator. We have used three separate Aquator models initially developed by the Canal & River Trust as a starting point and worked to combine them into a single model to represent the whole scheme route. This represents inflows from gravity and pumped feeders into the canal network, as well as water losses and movement due to lock operations, leakage and evaporation. This allows us to model present-day and future scenarios over very long time periods including periods of both drought and flood. The model is being verified using an extensive hydrometric survey, also delivered by JBA, as well as historic flow and level data.

Flows from the Aquator model form the flow boundaries into the hydraulic model, built in Flood Modeller Pro (FMP), which we are using to test the impacts of the transfer on water levels, the velocity at constrictions and overflows into rivers.

The transfer flow will come from Severn Trent Water’s Minworth wastewater treatment works, one of the UK’s largest. The FMP Water Quality module is being used to test the impacts of the transfer on water quality along the lengths of the transfer route, helping to identify treatment permit levels that prevent deterioration and where possible improve water quality in the canal. This information can be fed back into the design of the additional treatment processes which will be required at Minworth to support a discharge into the canal.

Benefit

  • We are working as an integrated design team with the clients plus engineering (WSP) and environment (Mott MacDonald) consultants to direct the modelling to answer key questions about the hydraulic and water quality impacts of the transfer.
  • This has identified a set of “test cases” where we are using extra-detailed models of small sections to answer specific questions.
  • We have developed and calibrated new hydrologic models for several catchments feeding the canals.
  • We have developed a tool to transfer Aquator flow results to FMP inflows, enabling us to run several iterations of the proposed scheme.
  • Each step has involved adapting the application of the models to represent the unique nature of the canal and the proposed transfer, a challenge we are relishing.

Want to know more?

For more information about this project, please contact Paul Eccleston.



Leave a Reply