Exploring the link between urban development and water demand: The impact of water-aware technologies and options

In conventional urban planning, water demand is covered exclusively by potable water supply and wastewater is directly conducted to the sewers. One of the disadvantages of this practice is that the expansion of an urban area puts additional pressure on existing water infrastructure (both water supply and wastewater networks), which may result in capacity exceedance. In such cases, the required upgrades of existing infrastructure are slow and potentially very costly. On the other hand, modern decentralized water-aware technologies (including for example grey water recycling and rainwater harvesting) enable water reuse at the scale of a household or a neighbourhood. Such options reduce the pressure on the infrastructure and alleviate the need for upgrading centralized infrastructure, hence reducing the cost of urban growth. In an attempt to quantify the potential benefits of these technologies we coupled an urban water management model with a land-use model based on Cellular Automata (CA). The land-use model produces scenarios of urban growth/transformation, which are then assessed through the use of an urban water management model. The assessment is based on indicators including potable water demand, peak runoff discharge and volume of produced waste water. The final result is a representation of the evolution of these indicators as a function of urban growth contrasting conventional and innovative practices.