Observatoire des consommations d’eau urbaine. Application à Nantes Métropole

Since the 1990s, a drop in drinking water consumption has been observed in France. As a break after several decades of continuous rise in consumption, this decrease was not anticipated by local authorities and water operators. However, recent data at the municipal level for all of France confirm a slowdown in this downward trend or even a stabilization of consumption since 2013. These unanticipated developments and the importance of their impacts reinforce the need to improve knowledge of water demand and forecasting capabilities. This report presents an observatory project of urban water consumption developed in the pilot area of Nantes Métropole. A large number of analyzes were conducted thanks to consumption data collected and consolidated on behalf of the observatory. The first results confirm a continuous decrease in unit consumption between 2011 and 2017 for Nantes Métropole, although of very low amplitude. Data mining also highlights non-homogeneous consumption over time, in space and between different types of subscribers on the territory. In addition, these data, once linked to external data (socio-economy and household demography, housing typology, meteorology) were used to build demand functions at different local scales (cities and neighborhoods), which have been compared to a demand function built at national level. Regression results confirm the interest of going down to a finer scale, and therefore the relevance of using a local observatory to monitor users’ behavior and better anticipate them, to produce reliable indicators and useful parameters for consumption forecasting, and also to target public actions on certain user groups that would need to be specifically monitored.