The trigger for the new tougher water rules has been reached this week with Chaffey Dam, the main water supply, dropping to 35 per cent capacity according to council records.

Yesterday’s news also introduced a whole new watermark in relation to dam levels and official levels, but also marked the first time since 2007 that all outside water use was banned.

While Tamworth Regional Council was preparing to invoke the new rules and announce the latest restrictions on outdoor watering on Friday, it appears the government water authority WaterNSW, the owner of the dam, also invoked a new measure of its own which caught the council on the hop.

“They’ve transferred their accounting from the small dam to the larger dam,” Tamworth’s water director Bruce Logan admitted late yesterday.

It was a very simple explanation for anyone surprised by the fact the dam seemed to have lost over 8000 megalitres in the turn of a tap.

The council’s water division said WaterNSW appears to have changed the dam level capacity measures on Tuesday – because overnight their website database showed the dam moving from just over 35 per cent capacity to yesterday’s recorded 20.7 per cent.

The sudden change – suggesting the dam had dropped some 15 per cent in capacity – was explained logically and simply by the fact that WaterNSW has introduced the capacity and figurative measures that relate to the enlarged Chaffey Dam.

Work has been under way for about five years on the $44 million upgrade and augmentation of the dam – and its official completion to a new higher standard was marked earlier this month.

The murky issue of what capacity the dam was when it was smaller – or capable of holding 62,000ML – and how that translates to when you’re referring to the bigger dam – the 100,000ML version it now is – and the changeover has been a point of discussion at TRC for months.

“It has been a topic hard to explain, but somehow or other we had to get from the old trigger points to the new ones for a bigger dam,” Mr Logan said.

So, a few weeks ago, the council moved to mark how it would handle that quantum leap by deciding that once the dam dropped to 35 per cent capacity at the old level,  the tough Level 4 rules would come into place – from that point Tamworth water users would also abide by capacity levels relating to the “big dam”.

That measure has been met this week – coincidentally as the dam owner moved to the higher water mark, although TRC was waiting to move that way next week. But the question of watermarks is still an issue for TRC and its water boss.

Mr Logan says they’re waiting to hear back from WaterNSW – because he reckons with the changeover, the city has been shortchanged by about 1000ML.

Under the Logan and TRC computations, the 35 per cent mark on the smaller dam capacity should officially put the level of Chaffey at 21.7 per cent – a full 1 per cent above what the website is showing – and they’ve asked the water authority to explain the discrepancy.

Under the new rules, all outside use of town water is banned in Tamworth, Moonbi and Kootingal. If you want to use greywater, you have to use it with a bucket, and you can clean only your car windows with town water – obviously with a bucket.

Only council parks and gardens with bore water or recycled water supplies are allowed to irrigate their green spaces.

The Level 4 rules will affect close to 20,000 properties, including residential, commercial and industrial connections.