Multi-staged conversion from intermittent to continuous water supply

Abstract

About 2.2 billion people worldwide lack access to safely managed drinking water. These include approximately 1.3 billion, mainly in South Asia, Latin America, and Africa, that receive water for domestic purposes through piped networks for only limited durations in a practice known as intermittent water supply (IWS). The complex interactions of demographic (social), technological, economic, environmental, and political factors are the primary causes of IWS. They lead to higher water demand and Non-Revenue Water (NRW) water than supply systems’ capacity. Under IWS, the limited water resources are distributed to various zones at different times. In this way, as many consumers as possible can access water and water losses through leakage can be reduced. However, IWS poses high operation costs and NRW to water utilities, coping costs for water storage and treatment facilities to consumers and inequitable water supply, health problems and effects on children’s school activities to society. As a result, there is a great interest worldwide in converting from IWS to Continuous Water Supply (CWS). Achieving CWS is challenging for systems that are significantly degraded and require huge investments. Consequently, the conversion to CWS should be gradual and staged. Using the given pilot network, this study proposes an approach for converting from intermittent to continuous water supply by improving the network infrastructure in a phased manner over a period of 5 years according to the limited available financial and water resources. For hydraulic simulations, EPANET 2.2 was used. First, the network input file was modified by placing the leaks to their exact locations. Before starting the rehabilitations, the network operation was assessed. Rehabilitation was phased in five years and the activities involved were leak fixing, pump upgrades, installation of flow control valves (FCVs) at sources, and pipe replacements. These activities were implemented both manually and using codes developed in R and python. Four major indicators were used to assess the effects of the rehabilitation activities each year. The indicators were the proportion of the number of effective hours a subscriber is served (I1), the volume of water leakage (I3), the proportion of volume of water supplied to users(I4) and the level of equity in supply (I9). Through the staged rehabilitation, I1, I4 and I9 increased from 0.907, 0.757 and 0.733 to 0.995, 0.965 and 0.96 respectively while I3 reduced from 0.504 to 0.302.