South Australian government authorities have angered upstream irrigators by entering the market to buy irrigation water and use it in Adelaide.

A tender was quietly placed on a government website to buy up to three gigalitres of irrigation water from the Murray-Darling.

Two water broking services were engaged to make the trades.

The move angered upstream irrigation communities who were already questioning the amount of water being taken for the environment under the Murray-Darling Basin Plan.

Deniliquin farmer Shelley Scoullar, who is a member of the 'Speak Up' for irrigation communities, was "not happy" to discover water was being bought to take from the basin for tap water and flushing toilets in Adelaide when the city had other options.

"Maybe they should be using their surplus funds to turn on their desalination plant," she said.

Another irrigator who did not want to be named questioned South Australia's "moral stance for every drop of water being returned for the environment when it is buying water to use in Adelaide".

Irrigators are angry that South Australia is buying large amounts of water for Adelaide. ( ABC Rural: Warwick Long )

SA Water, the authority purchasing the water, would not reveal how successful its tender process had been.

"From time to time, SA Water purchases water on the open market to contribute to water security for our customers."

"Details of the purchase are considered commercial in confidence and are undertaken in accordance to the Murray Darling Basin Trading rules."

Water brokers the ABC have spoken to have said the company had paid at least $4500 per megalitre (there are 1000 megalitres in a gigalitre) for permanent water entitlements in New South Wales.