Sections of the Lower Sundays River Canal, which forms part of the Lower Sunday’s Government Water Scheme (LSGWS), in the Eastern Cape, is set to be closed for three months for urgent rehabilitation work.
The planned shutdown from June 10 to August 15, which impacts water users in the towns of Addo, Paterson and the Nelson Mandela Bay metropolitan municipality (NMBMM), is critical for rehabilitation work to be undertaken to ensure the reliability and sustainability of water supply to the users.
According to a joint statement by the Department of Water and Sanitation (DWS), Lower Sundays River Water User Association and NMBMM, parts of the 42-km-long Lower Sundays River Canal between Kirkwood and Addo will undergo the construction of canal tie-ins to a newly built section of the canal.
The repair of the canal is a result of a May 2017 incident where a section of the canal embarkment slipped about 4.4 km south of Enon, which subsequently led the DWS to construct a temporary embarkment using a plastic membrane to ensure the continuous supply of water to users.
However, a secondary embankment failure has now occurred, 200 m downstream of the initial embankment and canal failure, and if the damaged canal is not repaired, the water scheme will be at risk of collapse, the parties said.
The work includes demolishing the existing canal at the upstream and downstream tie-in sections, surface preparations, and the placement of a high-density polyethylene liner over the upstream and downstream tie-ins.
“It is important to note that, during the construction of the tie-ins, 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 to supply end-users.”
Measures have been put in place to minimise interruptions to water supply in these areas.
The LSGWS Canal system supplies two main users with bulk water, namely agricultural users in the Sundays River citrus producing area and domestic users in Kirkwood, Uitenhage, Enon and NMBMM, besides others.
The LSGWS also forms part of the greater Orange-Fish-Sundays Inter Basin transfer scheme and transfers 740-million kilolitres of water a year 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 NMBMM, which includes Gqeberha, Kariega and Despatch.
A portion of the Orange-Fish-Sundays Transfer Scheme supplies water to 20 000 ha of mainly high-value citrus crops, as well as the Nooitgedacht Water Treatment Works (WTW), which currently supplies 58-million kilolitres a year of water to the NMBMM, accounting for about 60% of the NMBMM’s water use.
The Caesar’s balancing dam, which supplies Addo and Paterson, will be filled prior to canal shutdown, and will be continuously recharged during the intervals when the canal is opened.
The NMBMM, 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 offset by increased supply from the Western systems through the Loerie and Churchill dams and the Loerie and Elandsjacht WTWs managed by Gamtoos Water User Association and the metropolitan, respectively.
The Loerie and Scheepersvlakte balancing dams will be filled to 100% capacity before the shutdown starts and refilled during open flows.
Kirkwood, which is located upstream of the shutdown point, will continue to be supplied from the main canal.
DWS said it had consulted extensively on the planned shutdown to bring all its stakeholders on board and for 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 as the planned shutdown gets implemented.