Investment feasibility analysis of rainwater harvesting in the city of Itapiranga, Brazil

This study presents an investment feasibility analysis of rainwater harvesting in the city of Itapiranga, southern Brazil. The analysis was performed using the Netuno computer programme and daily rainfall data. Different catchment areas, daily potable water consumption, number of residents, coefficient of utilization and rainwater demand were simulated. By combining such variables, the potential for potable water savings as well as ideal tank capacities were obtained for 144 cases. For the investment feasibility analysis, costs of system components were obtained from local stores. Water and electricity tariffs were obtained from the local utilities; monthly potable water savings and electricity costs due to the use of a motor pump were estimated. The net present value, the corrected payback and internal rate of return were then estimated. Only 45 cases were feasible; all of them for high potable water consumption and large catchment areas. Based on this study it can be concluded that rainwater harvesting, although not financially feasible for all cases, would contribute to high potable water savings. This would benefit society as residents would have a lower potable water consumption, and the public water utility would need to treat lower amounts of water. Therefore, there would be a lower environmental impact. Also, rainwater harvesting in Itapiranga would allow the creation of new jobs and need of experts on this field.