Potential environmental impacts of water harvesting systems for rain to emerging neighbourhoods in Colombia were studied. Two tools were integrated into a simulation model (life cycle analysis and system dynamics). This was performed as an application case study in two urban areas of Colombia (Bogota and Pereira). We modelled a standard neighbourhood with 10 residential 5-storey buildings of 24 apartments. The results show that it is possible to avoid in every neighbourhood 150,729 kg CO2e and 44,857 kg CO2e, respectively.