Development Of Optimised Conjunctive Control Rules For A System Of Water Supply Sources (1997-1998)

Funding body: Environment Agency

Control rules have been used in the United Kingdom for more than 50 years to reduce operating costs by controlling the overdrawing and pumped refill of reservoirs. However, for over 25 years some water companies within the UK have been integrating their sources into resource zones so there has been a need to produce conjunctive control rules applying to a whole system. This is undertaken to achieve greater economic returns, a higher reliability of supply and to provide a clear view about the 'spare' resource within a system.

The derivation and construction, whether formally or informally, of reservoir operating control rules within the Environment Agency South West region has been based on a methodology described in The British Hydrological Society Occasional Paper No.1 (1988). This technique is able to deal adequately with the operation of single reservoirs. However, although some guidelines on the operation of multi-purpose, multiple reservoir water systems have been devised, there remains no methodology generally accepted by water resource managers for deriving multiple-reservoir operating policies.

This research developed a new approach to the optimisation of the operation of multiple reservoir systems. The revised methodology develops the concept of an extended drought period with an additional emergency storage reserve to extend the reliability of the system. The operation of the Roadford Reservoir System, South West England, consisting of nine reservoirs was studied. Through simulation analysis, the control rules of each reservoir were revised to achieve the targets to the maximum possible extent. The obtained results are superior to the current operating control rules, in terms of reliability of supply and the volume of demand deficit in Roadford Reservoir System over a 116-year historical data set.


  • Thorne, J.M., D.A. Savic and A. Weston, (2002) Optimised Conjunctive Control Rules for a System of Water Supply Sources: Roadford Reservoir System (UK), Water Resources Management (in press).
  • Thorne, J.M., D.A. Savic and A. Weston, (1999) Development of Optimised Conjunctive Control Rules for a System of Water Sup-ply Sources, in Making Better Use of Water Resources, CIWEM, London, pp. 141-155.
  • Thorne, J. and D. A. Savic, (1998), Development of Optimised Conjunctive Control Rules for a System of Water Supply Sources, Centre for Water Systems, Report No.98/02, School of Engineering, University of Exeter, Exeter, United Kingdom.

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