Sustainable Water Management Solutions for Large Cities (Proceedings of symposium S2 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 293, 2005, 155-163

Pontifícia Universidade Católica do Paraná (PUCPR), Civil Engineering Department and Universidade Federal do Paraná (UFPR), Hydraulics and Sanitary Engineering Department, Curitiba, Paraná, Brazil

Abstract A project consisting of a collection area, a storage tank and a rainwater utilization system, in a family house, with 51 m² of collection area (the roof), was developed to utilize 85% of the 1526.6 mm average annual rainfall observed in Curitiba City, capital of Paraná State (Brazil). The rainwater storage tank capacity was determined from the collection catchment area 20.5 mm m^-2 = 20.5 l m^-2. This criterion is the regional superficial coefficient of the rainwater collection areas in Curitiba City, developed to promote rainfall detention, to decrease the maximum level of urban floods, retard the surface flows, and recharge the groundwater in catchments with highly impermeable drainage areas. Water from the rainwater storage tank used for non-drinking purposes: internally for toilet flushing and externally, e.g. washing a car, sprinkling impermeable pavements around the house and watering plants, in a four-person family house was estimated, and then the monthly economies and the total annual saving caused by the substitution of drinking water for rainwater were estimated. The average annual economy of drinking water was estimated in 28.5%. The budget applied in the construction of the rainwater utilization system with drinking water rationalization and water resources conservation, presented an average investment refund period of 5 years.

Key words detention and rainwater utilization; economy of drinking water