The basis of the source head method of calculating distribution network reliability

This paper formalises the derivation of the hitherto intuitive source head method of calculating water distribution network reliability. The derivation is inspired by recent developments in pressure-driven network analysis. The reliability analysis uses a parameter referred to as the required source head for full demand satisfaction together with the widely accepted definition of reliability as the expectation of the ratio of available flow to required flow. The methodology is conceptually simple and straightforward to implement. The calculated reliability values are probabilistic in that the random nature of pipe failures is accounted for. The computational efficiency of the formulation is very high, and this is demonstrated using a sample network. The results suggest that if reliability is calculated as the average of the upper and lower bounds, large savings in computational effort can be made.