The London Water Ring Main is one of UK's largest water investments. It will eventually carry half of London's water and greatly increase the flexibility of London's trunk distribution network. The Trunk Scheduling System is a core part of decision-support for the enhanced network. It has been written to help Operational Controllers make best use of that extra flexibility.

Cost-effective operation makes best use of the cheapest treatment works, lowenergy-loss routes and off-peak tariffs. These need to be combined to meet projected diurnal demands in over 50 zones and leave each of some 20 service reservoirs at a target end volume, whilst taking no more than the declared “reliable output” from each of 10 works. The schedule proposed must be hydraulically viable as well as cheap. Most route constraints arise from pressure limits (so as not to burst mains or leave customers without water). Hydraulic constraints are non-linear and require on-line hydraulic intelligence as the schedule is developed.

The key idea is to regard a schedule as a series of “operating regimes”, each of which is applied for a specified duration. Each regime applies within a particular timeslice. It comprises settings for each pump in the network, together with its implications: a unit cost and the effect of those settings on each source and each reservoir under hydraulic equilibrium. Trunk Scheduling provides a series of modules to answer the questions:

  • which regimes (of the billions possible) should make up the schedule?

  • how long should each selected regime be applied for?

  • in which sequence should the chosen regimes be applied?

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