Construction on the Clanwilliam Dam wall is set to start on Monday after years of delays and allegations of corruption.

Water and Sanitation Minister Gugile Nkwinti announced on Thursday that he would "turn the first sod" in a ceremony that would mark the start of construction.

The R2.5-billion project will raise the dam wall by 13m, which would double its capacity and provide enough additional water to irrigate a further 5 000ha of farm land.

It will create an opportunity for the expansion of high-value export crops and stimulate economic growth in the region.

The land is likely to be used to accommodate emerging commercial farmers.

The bigger dam will also increase the amount of water available to local municipalities in an area that has been savaged by a three-year drought.

Rerouting of N7

Head of Agri Wes-Cape Carl Opperman said in response to the announcement: "Hooray! Something is happening at last."

The project had been due to start in 2013 and was scheduled to be completed around July this year, but it never got off the ground.

The preparatory work was done years ago, including the rerouting of the N7 that would have been flooded otherwise once the wall had been raised.

Opperman said the additional 5 000ha of land that would have access to irrigation water would most likely be developed in conjunction with the land reform programme.

"It can be developed for high-value export crops such as wine, table grapes and oranges. The extra water is good news for economic growth, for stability in the water sector and in the face of climate change.

"It will create work for people in the area and be a big push for development," Opperman said.

Decision taken more than a decade ago

He said it was likely that existing farmers would create partnerships with emerging farmers to work the additional land.

The decision to raise the wall was taken more than a decade ago after a routine survey by the Department of Water and Sanitation that checked the structural safety of the country's old dam walls.

Originally, the Clanwilliam project was budgeted for in the department's 2013/14 budget and was to be built by a departmental team. This changed and the department decided to put the project out to tender.

Western Cape Premier Helen Zille wrote earlier this year that "speculation was rife at the height of the Zupta vice grip on power that a politically connected consortium had the project in its sights".

The tender was never awarded and lapsed.

Zille wrote that when she raised the matter with former water and sanitation minister Nomvula Mokonyane, she was told there was no money for the Clanwilliam Dam project as the money had been "moved somewhere else".

After President Cyril Ramaphosa appointed Nkwinti as water and sanitation minister in late February, Nkwinti gave an undertaking that the Clanwilliam project would go ahead in October.

Ramaphosa has tasked the Special Investigating Unit to investigate the Department of Water and Sanitation for alleged serious maladministration in the procurement process and for improper and unlawful conduct.

The investigation will focus on the period from January 2015 to the present.