Civil Engineering October 2022 | Vol 30 No 9

22 October 2022 Civil Engineering Q Q Intermittent supply can create water quality problems and in some cases increase the incidence of water-related diseases such as diarrhoea, typhoid and cholera. Q Q Implementing intermittent supply can be achieved in a matter of hours, but returning to a reliable 24/7 pressurised supply can take years due to the damage caused to the network. Q Q Water service providers that have resorted to intermittent supply may find that returning to a 24/7 pressure regime will prove to be extremely difficult and costly, requiring both political and institutional support that is often lacking. “A paradigm shift is imperative” (Charalambous, 2016). Q Q Intermittent supply is not an ap- propriate long-term intervention for reducing water use or water losses. RECOMMENDATIONS The following recommendations should be considered: Q Q Water service providers should implement water saving measures (WRC, 2014) and/or restrictions early on in a drought to avoid having to take emergency measures when water supplies can no longer support the demands. Q Q Reducing water pressures to below the acceptable norms in order to maintain a 24/7 pressurised supply is preferable to introducing an intermittent supply. Liaison with the fire department will be helpful in such cases to address liability and insurance issues. Q Q Properly sectorised networks with clearly defined and controlled pressure zones have the added benefit that pres- sure can be used to control water use during severe droughts. Water service providers should therefore be encour- aged to set up and operate such zones during normal operating conditions so that the necessary infrastructure is in place when needed. Q Q Intermittent supply should be the op- tion of last resort. Q Q It is accepted that in certain crisis situations, there may be no alternative to intermittent water supply, such as in the case of KwaZulu-Natal when severe floods caused huge damage to the water infrastructure. In such cases, great effort is required to mitigate the health issues until a fully pressurised water supply can be restored.  REFERENCES Charalambous, B. 2016. Intermittent Water Supply in Water Distribution Networks. Water Loss 2016, Bangalore, India. Water Research Commission (WRC). 1999. Development of a standardised approach to evaluate bursts and background losses in water distribution systems in South Africa: SANFLOW . Report TT109/99, by R Mckenzie to the South African Water Research Commission. Water Research Commission (WRC). 2014. Guidelines for Reducing Water Losses in South African Municipalities. Report TT 595/14 by R Mckenzie to the Water Research Commission. Intermittent supply will eventually result in greater water use than 24/7 pressurised supply, assuming that the resource is capable of supporting the demand from the system. Figure 5 Intermittent supply compared to pressurised supply Flow (m 3 /h) 450 400 350 300 250 200 150 100 50 0 Mon 00:00 Tue 00:00 Wed 00:00 Thu 00:00 Fri 00:00 Sat 00:00 Sun 00:00 100 150 200 250 300 350 400 : : ri : t : m( wolF 3 /h) Initial Average Flow: 135 m 3 /hr Reduced Average Flow: 95 m 3 /hr