Design of rainwater harvesting storage through efficiency and cost elasticity: case study Santander University

ABSTRACT Reliability analysis is usually required as input for feasibility assessments of rainwater harvesting (RWH) systems. This study introduces the concept of elasticity between the volumetric reliability and a cost function to optimize the storage capacity. The elasticity was estimated for three tanks at a campus of the Universidad de Santander, Colombia; by means of a daily water balance under specific conditions of demand (non-potable uses), infrastructure (area and coverage of surface), and climatic variability. This method showed that, the average expected efficiency ranges from 29% to 58% with tanks of 60 m3. These values are 7–10% lower than those expected just from the water balance, but the size of tanks decreases by up to 53%. Therefore, the present method allows not only a comparison between expected efficiencies from average estimations with the optimization from daily water balance, but also with that estimated in conjunction with costs.