Paper Title
The Long-Term Behavior of Residential Rainwater Harvesting Systems in 1969–2018 Rainfall Time Series

Increasing pressures on water demand and availability of water resources due to progressive urbanization, industrial development, population growth and climate change require looking for water sources. A significant part of the water demand in residential buildings can be reduced as a result of replacing tap water with rainwater. This study aimed to investigate the potential of rainwater harvesting (RWH) system performance for polish climate conditions, on the example of two cities: Białystok and Wrocław. The inflow, outflow and the storage volume of rainwater were evaluated on the basis of water balance model including 1969–2018 rainfall data and water consumption estimated for two purposes: toilet flushing and washing. The simulations revealed that RWH system is able to cover ~80% of annual water demand. The accumulated rainwater can fully cover the water demandfor two-thirds of the year. Therefore, RWH systems can definitely play a significant role as an alternative water source and should be implemented as a common practice in urban development. Keywords - Rainwater Harvesting, Water Demand, Water Saving Efficiency, Water Balance Model.