Re-design of a water distribution system using a stochastic approach. A case study of Bujuuko Town, Mpigi district.

Abstract

Water is an essential element required for the sustenance of plant, animal and human life and the development of human civilization (Falkenmark, 2020). In modern communities, it is more specifically important for: domestic, industrial and commercial use (MWE, 2013). At least 300 million people around the world are served by intermittent water supplies were the pipes do not supply water for periods of time (Nelson et al., 2016). Traditionally, in water distribution system design, the systems are designed to be able to handle demands at the end of their design period, usually 20 years (MWE, 2013). In this design, water demand throughout the design period is considered to be deterministic, which means, involving no randomness (Basupi & Kapelan, 2015; Vertommen et al., 2012). This assumption makes the systems susceptible to poor performance since the actual demand at each node in a WDS is not usually known with accuracy, especially when considering long-term projections (Giustolisi et al., 2009; Magini et al., 2016). In Africa many water utilities are working hard to expand access, but most cannot keep up with the growing water demand. This has left only one third of urban residents with piped water to their homes. Hours of water supplied tend to be less than 24 hours per day. Many utilities provide relatively low levels of service compared to utilities with a much larger reliance on shared connections and public stand posts (Berg, 2017). The authorities responsible for water supply in Uganda are the Ministry of Water and Environment and the National Water and Sewerage Corporation (Danilenko, 2021) whose role is to ensure availability of adequate water to meet the people’s demand. In current practice design of WDN in Uganda is with accordance of the Uganda Water Supply Design Manual. Uganda has one of the fast growing populations. Lutaaya & Echelai (2021) reported that between 2007 and 2020, water customer connections base of Kampala has more than tripled from about 95,000 customers in 2007 to 345,000 customer connections in 2020, an increase which was not foreseen in the design of the system and thus warranted the use of intermittent water supply (IWS) in Kampala. Water supply has not kept pace with the population growth and has resulted in water shortages and low pressures in most parts of distribution system (Mutikanga et al., 2011). Owing to such unpredictability in the nature of water demand, WDS design approaches that take into consideration demand uncertainties are recommended.