The Influence of Deep Uncertainties in the Design and Performance of Residential Rainwater Harvesting Systems

Abstract

The Rainwater Harvesting Systems (RWHSs) have being used as water conservation alternative to guarantee access to water in urban areas facing increasing demand and climate variability. However, the functioning of these systems depends on socio and economic parameters that usually are de ned as constant in traditional viability analyses. The variability of these parameters are not well represented by prede ned probability functions, being named in the literature as deep uncertainty factors differentiating from well-characterized uncertainties whose probability functions are known. This research aimed to evaluate the in uence of uncertainties (deep and well characterized) in the performance of RWHSs in three towns in the State of Goiás, Brazil (Rio Verde, Ipameri and Formosa). Technical (Satis ed Demand -SD, Reliability -REL and Rainwater Consumed -RH) and economic (Net Present Value -NPV, Net Present Value Volume -NPVV and Bene t Cost Rate -BCR) performance criteria were evaluated under a set of 1,000 scenarios comprised of climate (rainfall) and deep uncertainty factors (water tariff, discount rate and operational costs). According to selected performance criteria, the RWHS performed well in 50. 01%, 46.19% and 38.01% of the scenarios in Rio Verde, Ipameri and Formosa, respectively. It was possible to illustrate the impact of the water tariff and the discount rate in the performance of RWHSs in all three cities showing the need to incorporate the variability of these parameters when evaluating RWHSs as alternative source of water supply in urban areas.