Three sensitivity analysis methods based on derivative, screening and regression are applied to the CLARA simplified planning tool (CLARA-SPT) estimating life cycle cost (LCC) of water supply systems. Derivative-based and standard regression coefficient methods are used to address parameter prioritization and Morris screen method for parameter fixing. The study investigated sensitivity of 26 parameters through three feasible water supply alternatives. The results revealed the importance of all global parameters: period of consideration, net interest rate and expected annual growth rate, for the LCC of all alternatives. The analysis identified ten technological parameters as non-influential, which can be fixed to a certain value. In contrast, two internally fixed parameters (i.e., chlorine dosage and alum dosage) are determined to be important; hence, these parameters need to be available for planners for reasonable cost estimation. Except for period of consideration, all parameters have low standard deviation (σ) value that indicates linear correlation of alternatives' LCC with input parameters and/or insignificant interaction among parameters. This study is valuable for further development of the CLARA-SPT in order to simplify it and to provide guidance for the tool user on the importance of specific input parameters.

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