Some potato farmers are stealing water in the water-stressed Sandveld region of the West Coast that already has an annual deficit of six million cubic metres of water.
And in what is described as a very worrying trend, many of the boreholes that supply all the water for four municipalities in the Sandveld - Lambert's Bay, Elands Bay, Graafwater and Leipoldtville - are now producing less water or water of a deteriorating quality.
This emerged at a report-back meeting at the Elands Bay Hotel this week where consultants for the department of water affairs and forestry revealed some preliminary results of their work to determine the statutory water reserve for this area.
The output of some of the boreholes have dropped dramatically, and in the worst case, the groundwater levels in the Jakkalsvlei area supplying Lambert's Bay are down by as much as 14m.
Several other boreholes in the Wadrif-saltpan area, which also supply Lambert's Bay, are now four metres below sea level, prompting fears that there could be an inflow of seawater into the aquifers (underground freshwater stores) feeding the boreholes.
The water from some Sandveld boreholes has deteriorated to undrinkable levels in terms of SA Bureau of Standards quality recommendations, and some Sandveld wetland areas are deemed already irreversibly damaged.
Potato farmers have been warned that unless they agreed to voluntary cutbacks in their water use and to share the water resource with emerging farmers, this will be forced on them by the government - and that some boreholes might even be closed.
In terms of the National Water Act a reserve must be established for each catchment area to determine how much water must always be left in the system to maintain its natural ecological integrity and to provide for basic human use, calculated at 25 litres per person per day. Only then can any excess water be allocated for uses like crop irrigation.
While several speakers at the meeting referred to the water crisis in the Sandveld, the consultants also pointed out that a few boreholes in this region were actually showing bigger yields or an improved water quality, and some boreholes still produced excellent quality water.
The Sandveld was a resilient system and there were examples of areas that had returned to their natural status where water abstraction had been stopped.
I don't want to paint a totally negative picture - if we start managing it (the water resource now), it's not all doom and gloom, said Julian Conrad of the Stellenbosch-based company heading the study.
The Sandveld is bounded roughly from the Olifants River in the north, the Atlantic Ocean in the west, the Berg River to the south, and the Piketberg and Olifants River mountain ranges in the east, and the study concentrated on six sub-region catchment areas in the heart of this area.
The major agricultural activity here is potato farming on irrigated circles, and the extent of land cleared for these circles has rocketed since 1993.
About 80 percent of all Western Cape applications to clear virgin veld for new agricultural production come from Sandveld farmers of whom 170 produce about 15 percent of South Africa's table potatoes and 38 percent of the country's seed potatoes.
Because of the extremely low rainfall in the Sandveld - it gets less than 200mm a year - and the extremely low nutritional value of the sandy soil, all potato crops are irrigated and heavily fertilised.
Potato production uses on average 7 000m3 of water per hectare per year. There are 1 727 irrigated production circles, mostly used on a four-year rotational basis.
The clearing for potato production is of huge concern to environmentalists, because of water use and the unique natural fynbos and renosterveld vegetation that is destroyed.
Abdulla Parker of the Western Cape regional office of the department of water affairs and forestry told the meeting that the Sandveld was a stressed catchment with a water deficit of six million cubic metres a year.
The total amount of water available was 32 million cubic metres, but the requirement was already 38 million cubic metres - including 35 million for irrigation.
Because of the high level of extraction, there was a big risk of seawater intrusion into the aquifer, and there was a real need for aquifer protection, monitoring of groundwater resources and well-field management.
We need to talk about reducing water and we will close boreholes as a last option, Parker warned.
Pointing out that the department was negotiating with the Potato Growers Association to help it manage the Sandveld's limited water resources, he added: We all know there is illegal water use in the Sandveld.
While some of the many potato farmers in the audience were defensive about their crop, others were supportive of moves to manage water properly.
One of them was Hansie Genis of Graafwater, who said a farmer allowing his land to degrade was like taking a R1,2-million Mercedes to the dodgem cars.
A Sandveld farmer's biggest assets are his underground water and his soil, he stressed.
Conrad said the reserve determination report, to be completed within a few months, would lead to a sound management plan.