That is one eighth of Adelaide's daily drinking water.

The Renmark grape grower has allegedly stolen $20,000 worth of irrigation water, an offence that carries a maximum penalty of up to 10 years imprisonment.

The South Australian opposition leader Martin Hamilton-Smith said that hundreds of gigalitres of water from the Murray had been stolen through unmetered pumps for some time.

In August, shadow agriculture minister Adrian Pederick found that eight times the amount of Adelaide's drinking water had been diverted from the Murray through unmetered pumps.

"People were telling him that, in NSW, officials are going around and virtually giving the tick to illegal diversions and pumps," Mr Hamilton-Smith said.

Federal Water Minister Penny Wong has also warned that more water is needed to save the lower lakes in SA.