Household Water Withdrawal Behaviour under Intermittent Water Supply

Piped networks are the predominant method of distributing water to households in urban areas. In many cities across the world, the piped network operates intermittently with water supplied for less than 24 hours per day. These Intermittent Water Supply (IWS) networks are estimated to affect over one billion people worldwide, predominantly in the Global South. Operating intermittently requires households to adapt their water withdrawal habits in order to manage their access to water, for example, storing water for the ‘dry pipe’ periods. The effects of IWS are not felt equally amongst the served community as intermittent operation causes unequal distribution of water across the network.
Efforts to better manage IWS networks and, if possible, transition to continuous ‘24/7’ water supply are hampered by the current lack of models that can simulate IWS behaviour accurately. A significant obstacle is the paucity of data regarding household withdrawal behaviour, a key driver of the water dynamics in a piped water network. This study aimed to investigate the influence of supply conditions and household characteristics on water withdrawal behaviour under IWS conditions
A comprehensive data collection programme in an operational IWS network enabled new insights that can unblock progress towards effective management of IWS systems. In partnership with The Beacon Project, the IWS network of Lahan, Nepal was monitored in greater detail than any previous study. A series of 56 household volumetric flow meters were installed coupled with a household survey and pressure sensors distributed across the network. Together they form a first-of-its-kind dataset revealing the dynamics of an IWS network.
The data revealed ‘pooling’ phenomena where water drains down the network and sits at the lowest elevations, leading to a portion of Lahan receiving continuous water supply. Households employed a range of adaptations that were influenced by both their wealth and local supply conditions. Highly variable withdrawal behaviours were observed; the specific withdrawal signature of a household was strongly associated with their volume of storage. Current simplifications utilised by modellers do not accurately reflect this highly heterogeneous and coupled behaviour.
The quantity of water that households withdraw was not found to correlate with their local supply hours suggesting a more complex relationship between household water demand and IWS conditions. Widespread use of other water sources complicates the notion of ‘consumer demand satisfaction’, leading to a proposed separation of piped water demand and total water demand. Analysis of the Lahan case study led to the development of a new framework that describes the relationships and processes that govern water access under IWS supply. The framework highlights the crucial intersection of supply conditions and household adaptations to determine inequitable access to water. This has wide-ranging implications for hydraulic models of IWS, long-term demand forecasting and network management approaches.