On a 23 ha urban watershed, 10 km East of Paris, rainwater tanks have been installed on 1/3 of the private parcels to prevent stormwater sewer overflows. This paper investigates the macroscopic effect of rainwater harvesting on runoff, and thus the potential of this technique for stormwater source control. The analysis is performed using the SWMM 5 model, calibrated on rainfall- runoff measures from two measurement campaigns, before and after the equipment. The availability of two data-sets allows the authors to point out changes in the catchment's behaviour. The main findings are that: (1) catchment's evolution, mainly caused by individual land-cover modifications, produces non-stationarity of the hydrologic behaviour; (2) the rainwater tanks installed, although they affect the catchment hydrology for usual rain events, are too small and too few to prevent sewer overflows in the case of heavy rain events.

The practice of rainwater harvesting (RWH) is spreading rapidly in urban areas. This article studies the impact of a possible generalization of this practice for municipalities by proposing a new method to quantify the potential for potable water savings (PPWS) by using rainwater harvesting at the urban level. The proposed method is based on the adaptation of an already validated model assessing the PPWS for single buildings and the use of urban databases. Two concepts are introduced: (1) the “building type” that allows gathering all the buildings sharing common features; and (2) the “equivalent building,” which is used to assess the PPWS of a set of buildings (of a same building type) as if it were a single building. In the case of the municipality of Colombes (located in the suburbs of Paris), the method shows that the PPWS by using rainwater harvesting represents about 10% of the total potable water consumption: the residential buildings account for 64% of this potential. This method can be applied to other municipalities with a level of acceptable reliability with regard to the means to be implemented in terms of collecting information.

This document proposes a methodology for assessing the quality of water distribution service in the context of intermittent supply, based on a comparison of joint results from literature reviews and feedback from drinking water operators who had managed these networks, with standards for defining the quality of drinking water service. The paper begins by reviewing and proposing an analysis of the definition and characterization of intermittent water supply (IWS), highlighting some important findings. The diversity of approaches used to address the issue and the difficulty of defining a precise and detailed history of water supply in the affected systems broadens the spectrum of intermittency characterization and the problems it raises. The underlined results are then used to structure an evaluation framework for the water service and to develop improvement paths defined in the intermittent networks. The resulting framework highlights the means available to water stakeholders to assess their operational and management performance in achieving the improvement objectives defined by the environmental and socio-economic contexts in which the network operates. Practical examples of intermittent system management are collected from water system operators and presented for illustration purposes (Jeddah, Algiers, Port-au-Prince, Amman, Cartagena, Barranquilla, Mexico, Cancun, Saltillo, Mumbai, Delhi, Coimbatore …).