This research investigated the relevance of four hydrological variables in the performance of a domestic rainwater harvesting (DRWH) system. The hydrological variables investigated are average annual rainfall (P), precipitation concentration degree (PCD), antecedent dry weather period (ADWP), and ratio of dry days to rainy days (n(D)/n(R)). Principal component analyses are used to group the water-saving efficiency into a select set of variables, and the relevance of the hydrological variables in a water-saving efficiency system was studied using canonical correlation analysis. The P associated with PCD, ADWP, or nD/nR attained a better correlation with water-saving efficiency than single P. We conclude that empirical models that represent a large combinations of roof-surface areas, rainwater-tank sizes, water demands, and rainfall regimes should also consider a variable for precipitation temporal variability, and treat it as an independent variable. (C) 2016 Elsevier B.V. All rights reserved.