But, in the space of a couple of days, it appears Tamworth has officially got something even bigger than they bargained for.

It's official this week Chaffey Dam is actually a couple of thousand megalitres bigger than anyone's been talking about since the dam augmentation was announced some five years back.

The news has taken some by surprise mostly anyone who's been reporting on the project and certainly users, including the Tamworth council.

But it's been a surprise greeted with general good grace. We've got a bonus, an extra 2868 megalitres in the pool of water.

Until Thursday, when WaterNSW confirmed it, the newly-enlarged Chaffey Dam had always been put at a capacity of 100,000 ML, up from the original 62,000ML of the old dam.

That's created a couple of little ripples, not least because new water plans and importantly drought- and water-control plans have been drawn up by Tamworth Regional Council, which has thrown them some wobblies to wrestle with, particularly with their new drought-management plan, adopted only last month.

The trigger levels for when Tamworth moves between restrictions and different watering rules is set out in black and white in that 60-page document, but based on the 100,000 megalitre capacity.

Tamworth Regional Council water chief Bruce Logan said yesterday the plans would need to be adjusted but there also needed to be some examination of the new levels as well because, on the face of it, they need to clarify exactly whether Chaffey is sitting at the WaterNSW figure, when their figures suggest it should be 1 percent more.

That 1 per cent is critical, because, under the new plan, when Chaffey now falls to 20 per cent, that triggers the emergency Level 5 rules.

That's likely to be reached in about a week, if Tamworth consumers continue to use up the same amount of water they have been for the past few weeks.

Level 5 doesn't mean much difference to the ordinary householder or domestic user but it does call for more commerce and industry to cut their consumption patterns by another 25 per cent.

Over the past five or six years, there's been more than $55 million spent to upgrade and enlarge Chaffey Dam, with over $44 million on the latest augmentation and more recent upgrade works.

Tamworth Regional Council kicked in about $4 million of that $44 million.

Meanwhile, Tamworth water users are being asked to cut down their consumption alongside obeying new stricter outside rules that come into place today.

More than 20,000 water properties come under the new Level 4 restrictions, including Tamworth, Moonbi and Kootingal users of residential, commercial and industrial water from the city's treated system.

The new rules came into place when Chaffey Dam dropped to 35 per cent last week, a watermark figure in terms of new tougher rules, but also a switchover to the new Chaffey Dam total capacity point in the wake of the enlarged dam works being completed.

Under the new rules, all outside watering of properties is banned. About 15 high-profile council parks and gardens, including sporting fields, will still continue to be watered because they are all on bore water supplies or recycled systems.