In this paper, a fuzzy simulation–optimization model coupled with the genetic algorithm based on Boulton's equation is presented to estimate transmissibility (T), storage coefficient (S), specific yield (Sy) and leakage factor (Dt) of an unconfined aquifer. This model is capable of minimizing the deviation between observed and calculated drawdowns of pumping test data. To assess the applicability of the model, its results are compared with the graphically obtained solutions from Boulton's equation. To this end, real pumping test data obtained from an unconfined aquifer in Dayton, Ohio, are considered as the case problem to evaluate the efficacy of the model. In the fuzzy approach, pumping rate is considered as an uncertain variable. For evaluation of the model, several statistical error indices are utilized. Results show better matches for the model as evidenced by much smaller errors. As an example, mean absolute relative error for the proposed model and graphical Boulton's solution is 2.52% and 4.98%, respectively. It is concluded that the model is accurate and may replace the graphical Boulton's solution. T and Sy were found to be more sensitive to uncertainty in the pumping rate measurement, when compared with S and r/Dt.

This study presents a review of the state-of-the-art literature on water pipe failure predictions, assessment of water losses risk, optimal pipe maintenance plans, and maintenance coordination strategies. In addition, it provides a categorization of water main (WM) failures as well as a taxonomy of WM maintenance strategies. In particular, predictive and prescriptive analytics are highlighted with the investigation of their contributions and drawbacks from methodological and application perspectives. This review aims at providing a review of failure analytics developed recently in water mains domain either for prediction of failure or identification of optimal maintenance strategies conjointly. Future research directions and challenges are elaborated in advancing the understanding about the mechanisms leading to failures. The existing gaps between theory and practice in managing assets across water distribution networks ensuring cost-effectiveness and reliability are discussed. As knowledge about the state of the water mains and related areas is crucial, thus, this review provides an state-of-the-art update from recent studies, and accordingly, presents and discusses avenues for future research.

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