Water Balance Modeling as a Tool for Assessing the Inventory Flows of Urban Water Systems and Water Consumption in Buildings

A water balance modeling method was developed and applied to assess the water flow impact on urban water systems and water consumption in buildings. The method is based on the computational tool Aquacycle and a case study applied in a city in Brazil. Some modifications have been made to Aquacycle, including using urban drainage and sewage structures commonly applied in Brazil and parameters closer to the Brazilian reality. Such structures are decentralized wastewater treatment systems, deep tubular wells, irregular urban networks, and covered tanks for storing rainwater. Also, an automatic rainwater harvesting system was considered for flood mitigation. The water balance proposed may also be used for a modular assessment approach in urban water systems, aiming to facilitate the application of life-cycle assessment. A case study also aimed to assess alternative water supply in buildings, including scenarios with and without rainwater harvesting. The most significant positive impacts of using rainwater in buildings were a decrease of almost 6% in stormwater runoff and a decrease of water consumption by around 30%. There is a substantial waste of water in the distribution process, which, although it favors groundwater recharge, can have a high impact when considering energy and chemical products consumption. All contributions obtained via modeling can be used to provide specific fluxes in each component that can be used for technical, financial, or environmental evaluations, such as life-cycle approaches, carbon footprint, and cost–benefit assessment.