In North Otago, the Kakanui, Waianakarua and Shag rivers are all at low levels, and the majority of other rivers the Otago Regional Council monitors are considered to below normal for this time of year.
Council environmental information and science director John Threlfall said South Otago rivers the Tokomairiro and Waitahuna were also ''close to the wire'' for restrictions.
''We're down to summer conditions early on.''
However, forecasts for more rain in the headwaters of Otago's lakes and rivers this week meant the regional council was keeping a close eye on their levels for the opposite reason.
Heavy rain this week meant lake levels were already high but, if the rain came to fruition, it was not expected to cause any major issues, he said.
''We're keeping an eye on it.''
The Clutha River was at above-average flows, so there was a possibility it could rise or fall quickly.
Farmers along the lower Clutha River were being advised to move stock from alongside the river before they went on holiday, as flows were expected to reach 1000cumecs, Dr Threlfall said.
Campers and recreational river users needed to be aware of the conditions.
The low flow and dirty condition of the Catlins River led Tawanui (south of Owaka) resident Fergus Sutherland to raise his concerns with Fish and Game Otago and the Otago Regional Council last week.
''It's the lowest many of us have seen in a long time,'' he said.
Its colour was similar to that of the river in high flood, but it was only a ''dribble''.
''It is a bad look for visitors. It'll be disappointing if it stays like this.''
Otago Regional Council resource management director Selva Selvarajah said staff had checked the stream but had been unable to find any source for the discharge.
It had been observed that heavy rain in its headwaters combined with recently ploughed paddocks alongside the river might have contributed to its conditions, he said.
Otago Fish and Game chief executive Niall Watson said it appeared to be a significant event that could be the result of natural or man-made causes.
''Given the state of the river, it certainly needs to be tracked down.''
Silt in rivers smothered insect life which was the food of fish, and also disrupted recreational angling, he said.
Low flows in rivers, especially those without minimum flows, could lead to stress on fish life and even strandings.
Anyone who came upon fish strandings should contact Fish and Game, he said.
