Civil Engineering June 2022 | Vol 30 No 5

28 June 2022 Civil Engineering D evelopment of new water resources is urgently needed to both relieve the load on the Umgeni System and to meet growing water demands along the South Coast. As an additional primary source of potable water, LUBWSS will also increase the South Coast’s operational flex- ibility in the event of infrastructure damage arising from extreme natural events (the need for such flexibility being clearly dem- onstrated by the recent April 2022 floods in KwaZulu-Natal). The LUBWSS – Umgeni Water’s cur- rent flagship project – is expected to cost R5 billion when completed in 2026 and has three system components: 1. Goodenough System: Raw water ab- straction, desilting and pumping at the site of the old SAPPI-SAICCOR weir (on what was known as Goodenough Farm, some 12 km upstream of the Umkhomazi Estuary) and conveyance to a new water treatment works near Craigieburn. 2. Treatment and Clear Water System: Water treatment works (130 Mℓ/day capacity), clear water conveyance and Lower Umkhomazi Bulk Water Supply Scheme: Goodenough and Ngwadini raw water systems After many years of feasibility studies and detail design, Umgeni Water is currently proceeding with the construction of a river abstraction, conveyance and treatment system on the lower Umkhomazi River (the so- called Lower Umkhomazi Bulk Water Supply Scheme or LUBWSS) in order to augment the existing potable water supply to the KwaZulu-Natal South Coast. Figure 1 LUBWSS schematic layout Goodenough Reservoir Qdes = 1.19 m 3 /s (103 Mℓ/d) Qmax = 1.54 m 3 /s (134 Mℓ/d) Qdes = 1.19 m 3 /s (103 Mℓ/d) Qmax = 1.55 m 3 /s (134 Mℓ/d) Qdes = 100 Mℓ/d Qmax = 130 Mℓ/d WTW Quarry Reservoir SCS EWR = 1 m 3 /s SAPPI SAICCOR 1.7 m 3 /s 8.5% return Qdes = 1.30 m 3 /s (113 Mℓ/d) Qmax = 1.695 m 3 /s (146 Mℓ/d) Goodenough Abstraction Works High lift pumpstation Hydrocyclones and balancing tank Ngwadini Abstraction Works Summer Qdes = 1.0 m 3 /s Winter Releases to make-good river flow shortfall Ngwadini Dam Minimum river flow Goodenough abstraction = 1.16 m 3 /s Sappi-Saiccor abstraction = 1.7 m 3 /s Enviro reserve = 1.0 m 3 /s TOTAL = 3.86 m 3 /s Minimum river flow Ngwadini abstraction = 1.0 m 3 /s Goodenough abstraction = 1.16 m 3 /s Sappi-Saiccor abstration = 1.7 m 3 /s Enviro reserve = 1.0 m 3 /s TOTAL = 4.86 m 3 /s Umkhomazi River