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DWS postpones rehabilitation of the Lower Sundays Canal

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The Department of Water and Sanitation has announced the postponement of the emergency rehabilitation on parts of the Lower Sundays River Canal that was planned to start from Monday, 10 June to 15 August 2024.

This is due to the recent heavy rainfall that resultant into flooding in various areas of the Nelson Mandela Bay Municipality (NMBM) which may have compromised infrastructure including water supply systems. This to afford the municipality to complete its disaster assessment and response as well as state of readiness for the project resumption.

The canal is within the Lower Sunday’s Government Scheme (LSGWS) which forms part of the greater Orange-Fish-Sundays Inter Basin Transfer Scheme. The transfer Scheme conveys 740 million kilolitres of water annually from the Gariep Dam to Eastern Cape through the 80 km Orange-Fish Tunnel. In the Eastern Cape the water is controlled and conveyed through a system of dams, canals, tunnels, and rivers to supply 50 000 ha of irrigation as well as domestic water to towns such as Cradock, Somerset East, Bedford, Adelaide, Makhanda, Kirkwood, Addo, Paterson and the Nelson Mandela Bay Municipality (Gqeberha, Kariega and Despatch).

The portion of the Orange-Fish-Sundays (LSGWS) Transfer Scheme supplies water to 20 000 ha of mainly high-value citrus crops as well as the Nooitgedacht Water Treatment Works (WTW) of the NMBMM. The Nooitgedacht WTW currently supplies 58 million kilolitres of water to the NMBM annually, which is about 60% of the NMBMM’s water use.

The LSGWS Canal system supplies two main users with bulk water, namely agricultural users (Sundays River citrus producing area) as well as domestic and industrial users (Sundays River Valley Local Municipality and Nelson Mandela Bay Metro).

The Department had planned to commence with a construction of Lower Sundays River Canal tie-ins to the newly built section of the canal where a failure had occurred back in 2017.

The repair of the canal is a result of a May 2017 incident where a section of the embarkment slipped, resulting in failure of its optimal function between Kirkwood and Addo, about 4,4 km south of Enon. Subsequently, DWS had to put temporal embarkment using a High-Density Polyethylene (HDPE) membrane to ensure continuous supply to the users. However, a secondary embankment failure occurred, at around 200m downstream of the initial embankment and canal failure.

The work required to be undertaken during the period includes demolishing in the existing canal at the upstream and downstream tie-in sections, surface preparations, and a HDPE liner to be placed over the upstream and downstream tie-ins.

The total length of the new canal alignment is approximately 452 m long; this length incorporates the main embankment, the part where the canal failed as well as a section to bypass the secondary embankment failure.

It is important to note that during the tie-ins construction, the canal will not be completely shut down, but there will be intervals at which, upon completion of certain segments that are being repaired, water will be allowed to flow through to the dams for end users. During this period, on average, the canal will be closed for seven to ten days for construction and be opened for seven days for the flow of water to fill up dams for the areas to be impacted by the temporary shutdowns.

The major domestic users to be impacted by the canal supply interruptions will be the towns of Addo, Paterson and the Nelson Mandela Bay Metro (NMBM). However, measures are being put in place to ensure less interruptions to these areas. Kirkwood, which is located upstream of the shutdown point will continue to be supplied from the main canal. Addo and Paterson which are supplied from the Caesar’s Balancing Dam, downstream, which will be filled prior to canal shutdown, and continuously recharged during the seven days open flows.

The NMBM, which ordinarily receives 70% of water supply from the scheme through the Nooitgedaght WTW, will be supplied from the Scheepersvlakte Balancing Dam for the duration of the canal shutdown period. The reduced supply to the Nooitgedacht WTW will also be maximised from the Western systems through Loerie and Churchill Dams, and Loerie and Elandsjacht Water Treatment Works managed by Gamtoos Water User Association and the Metro respectively, to partially compensate the Nooitgedacht WTW. The Loerie and Scheepersvlakte Balancing Dams will be filled to 100% capacity before the shutdown commences and refilled during open flows.

Balancing Dams are designed to act as multipurpose reservoirs and are commonly used to serve as distribution points from where water is diverted into pipelines, canals, or to serve as pumping stations or store water for short period and immediate usage. The seven days closure and opening interval of the canal was determined based on the storage capacity of these dams.

Considering the developments, DWS will continue with its consultations on the new start date of the canal tie-in, to once again, bring all stakeholders on board to enable them to plan for this period and inform their customers. The Department continues to hold meetings with these stakeholders to discuss action plans to mitigate any possible challenges and bottlenecks when the planned dry period gets implemented.

It is important to note that the emergency rehabilitation to be carried out is critical for the reliability and sustainability of supply to the users. If the damaged canal remains not repaired, the scheme stands a total collapse.

DWS would like to appeal for cooperation during this critical period to ensure smooth operations that will result in completion of the work timeously and efficiently, and further urge all water users to use water sparingly during this period.

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