Nowadays, water management is necessary to optimize the use of this key
resource. As such, increasing water efficiency through the reduction of consumption
and/or resorting to alternative water sources is a challenge of the near future. Rainwater
harvesting is an accessible alternative source of water for non-potable and potable uses
in many parts of the globe. Rainwater can be collected easily and, in many cases, its
use may not require significant treatment, even for potable purposes. Yet, rainwater
harvesting (RWH) systems are still not common in most of the water supply projects,
namely in Mediterranean countries such as Portugal. The promotion of RWH systems
involves viability analyses estimating the expected water savings for different climate
and water consumption patterns. This chapter evaluates the performance of rainwater
harvesting systems of several case studies in Portugal, covering different water use
patterns and geographical locations. The water consumption pattern, both in time and
end-use, influences the potential for rainwater use. Water consumption was monitored
in residential buildings (a single family house and a building), a shopping centre and a
university building. Simulations are presented for different locations in Portugal, in
order to assess the influence of weather in the efficiency of RWH systems. In addition
to the rainfall amount, its distribution in time and space also contributes for the
rainwater availability. The operational data from an existing rainwater harvesting
system is used to calibrate the model and evaluate its sensitivity to the main
parameters. Tank optimization for each case study is discussed. The Mediterranean
climate, characterized by distinct wet and dry seasons and significant variability of the
rainfall events intensity and duration, shows substantial variation of the inter-annual
water savings from a rainwater harvesting systems. The results show that rainwater
harvesting systems in Portugal are a relevant alternative water source in different types
of building.
Keywords: Commercial buildings, Portugal, Rainwater harvesting, Rainfall
regime, Residential buildings, Simulation, University buildings, Validation, Water
consumption pattern, Water savings.
