A new study has shown that Johannesburg may have to re-evaluate their development priorities due to SA having 4% less water than previously thought.

A study was conducted on behalf of the Water Research Commission and has revealed water resources in SA to be 4% less than estimated in1995.

Future developments might have to be scaled back in order for water needs to be met, the study's project director, Brian Middleton, said .

Water use strategies may need looking into in the agriculture, forestry, electricity generation, industry, and groundwater developers sectors due to the findings.

Middleton said new mines and power stations might have to be put on hold as water would either not be available or would be too costly.

"We've behaved like a water-rich country when we're not. We're actually a semi-arid country and our mean annual rainfall is below the world average," Middleton said.

Water tariffs will also be affected by these findings, just what rate payers want after the recent increase due to the new

"We've probably underpriced water. I think we're like all humans: if you get something for free, you waste it," he said.

National water studies have been carried out since the 1950’s and have show a gradual decline in natural water resources.

As research techniques and technologies were improving all the time, the most recent findings tended to be regarded as the most accurate, said Middleton. Regular updating of statistics relating to water was vital to the country's water security.

According to the study, SA's mean annual runoff was just more than 49000-million cubic metres ; usable groundwater exploitation potential was estimated at about 10000-million cubic metres -- 25% less during drought s.

Middleton said that groundwater was used in probably 75% of the country's area -- mainly in small towns -- while larger urban areas used mostly surface water.

"The study's results suggest that there is merit in considering the conjunctive use of both sources . When surface water is available, we need to consider drawing on this more efficiently , allowing our groundwater reserves to build up for droughts."