An evaluation of the historical approaches to uncertainty in the provision of Victorian reservoirs in the UK, and the implications for future water resources planning

摘要

Attitudes to large Victorian reservoir schemes range from being unnecessarily grandiose to being grateful for a wonderful legacy. The sizing of three Victorian reservoir schemes at Thirlmere for Manchester, Lake Vyrnwy for Liverpool, and Elan Valley for Birmingham, was strongly influenced by ambitious Corporations, and the Victorian engineers’ judgment of the demand forecast, respectively JF Bateman, Thomas Hawksley and James Mansergh. In this research, the “risk averseness” of design size is used as a surrogate for uncertainty, and a novel lag-time method, which involves extraction of data from supply and demand balance diagrams, enables comparisons. The full Elan scheme design is found to be the least risk averse, and the original Thirlmere scheme design the most risk averse. In comparison with a contemporary large reservoir design, the tentative conclusion is reached that using the lag-time model approach, the recent proposal by Thames Water Utilities for a 100 Mm3 design for an Upper Thames Reservoir, in terms of future supply and demand, is a more risky design size than any of the Victorian designs. Water resources planners would be interested in the analysis and comparison of risk averseness and efficiency of design for other types of historical and modern schemes.