The Otago Regional Council is keeping "a very close eye" on the situation, and has advised water users to do likewise.
Low level alerts have been issued for the Taieri, Shag and Kakanui rivers.
Otago Regional Council environmental information and science director John Threlfall said yesterday recent rain had been "nothing like enough".
"It's just been a very dry year."
The situation would not change for the rest of the summer unless rains of long duration occurred.
The Shag and Kakanui rivers were covered by consents under the Resource Management Act, and farmers had to stop taking water if they ran below 0.25cumecs, and could not start taking water until they reached 0.4cumecs.
People would be prosecuted if they broke those rules.
Yesterday afternoon, the Shag at Craig Road was 0.1cumecs, the Kakanui at Mill Dam 0.5cumecs, and the Kakanui at Clifton Falls Bridge 0.5cumecs.
The Taieri River was running at 0.8cumecs, but operated under a quite different set of rules.
"The Taieri is a different kettle of fish," Mr Threlfall said.
Landowners there had historic mining privileges that were sold with the land, which were in place until 2021.
After that, they would come under the Resource Management Act.
Individuals and groups were already planning for that eventuality, and the council was assisting where it could.
Until then, the issue was "self-regulating", in that if there was no water in the river, there was none to take.
The privileges were on a first come, first served basis, where people further up the river could take what they wanted.
A "neighbourliness" system meant people did not run the river dry, but Mr Threlfall said some lower in the catchment did not always have enough water to take what they were allowed.
The council could order people to stop taking water, but that point had not been reached, and typically, in dry conditions, that made little difference.
The council would have another look at the situation in the New Year, and decide a course of action.
