Large-scale household rainwater harvesting: supply-demand analysis of the One Million Cisterns Program

The assessment of the supply-demand relationship in domestic rainwater harvesting systems has been much discussed. In particular, large-scale implementation programs would benefit from the availability of demand-supply indicators for the standard systems they implement. Such indicators should be simple, and, thus, of straightforward implementation, yet sufficiently informative to express the supply-demand relationship beyond the water balance. Hence, the aim of this work is to propose new indicators suitable for large-scale programs. Four indicators are evaluated: reliability, efficiency, resilience and surplus. The 1 Million Cisterns Program (P1MC) in Paraíba is taken as a case for the application and evaluation of the indicators. The standard P1MCsystems were numerically simulated, taking precipitation series for the 194 municipalities where the cisterns were implemented in Paraíba. The results show that reliability and efficiency, for these systems, have equivalent values, making it possible, without loss of information, to use only reliability.