Coast KZN

18 Oct 2021

Ugu provides update on proposed weir

Shona Aylward (South Coast Herald) Picture: A Google Earth image of the previous weir built along the river.

Ugu District Municipality’s new budget includes planning for a permanent abstraction berm/weir on the Umzimkhulu River. This is to upgrade and protect the Umzimkhulu River abstraction which is the life source for the Lower South Coast water supply from Hibberdene in the north to Margate in the south, Marburg, Bhobhoyi, Gamalakle and Murchison communities among others.

Ugu’s spokesman, France Zama said it is imperative to note that from inception of the Lower South Coast supply scheme more than 50 years ago, all planning, designing and authorisations have been geared towards sustaining the licenced potable abstraction of 32 million  m3 per annum from the river which necessitates a maximum system capacity of 108 million litres per day over the short peak demand holiday periods.

“An engineering study done in 2005, identified that a weir across the river is required for long-term assurance of flooded suction to the pumps, particularly during low meandering winter flows as well as to manage ecological reserve requirements,” he said.

Also, the weir would be required to synchronise and conserve water releases from Ncwabeni off-channel dam to be constructed 25 km upstream, as well as, a permanent solution to prevent saltwater contamination.

At a site visit in October 2020, the Minister of Water and Sanitation gave directives to Umgeni Water to fast-track the Ncwabeni dam with a storage capacity of 15 million m3 for release into the river in response to the increasing demand for water in the Ugu District with the St Helens Rock weir being an integral component of the scheme.

Mr Zama said the new weir and pipeline will be designed in line with industry best-practice with all protocols and compliance strictly observed. A hydraulic scale model of the river and weir will be constructed in the Stellenbosch University laboratory under the guidance of Professor Anton Basson, a leading hydraulic expert. Their 100 m long facility is one of the largest in the Southern Hemisphere where they have tested most of the recent similar weirs and river abstraction works constructed in South Africa, including the Umkomaas and Tugela River abstraction weirs amongst others.

Specialist studies will ensure that the current good health of the Umzimkhulu River and estuary are assured as an asset of the South Coast.

The weir allows river and sediment transfer to continue as per normal but ensures flooded suction for the abstraction pumps as permanent protection of supply against the vagaries of the river.

The Green Net has two upcoming public information meetings about the proposed weir. This Saturday, October 16 at the Melville Sanctuary of Love at 2 pm, and then next on Wednesday, October 20 at the Port Shepstone Country Club at 4.30 pm.