Government House, the Australian National Botanic Gardens, the Royal Canberra Golf Club and Yarralumla Nursery have been asked to reduce the amount of water they extract from Lake Burley Griffin for irrigation as the lake's level falls with the prolonged dry conditions.
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The Territory and Municipal Services-managed Weston Park and Black Mountain peninsula are also subject to the directive. So too are trees in the city watered from the lake. It is eight years since the measure was last in place and a sign of the tightening grip of the big dry, even with forecast rain.
The National Capital Authority has asked the abstractors to observe a 15per cent reduction in their permitted use of lake water from Monday.
The authority has applied the same measure to itself and the national land it manages and irrigates with the lake water.
The request for reduced use of water from the lake was last made in 2006. It was triggered because the lake level had fallen 20 centimetres below the Scrivener Dam spillway or the full point. Further falls in the lake level will result in further reductions in the approved water abstraction.
National Capital Authority chief executive Malcolm Snow said there were no penalties for abstractors who did not reduce their water use by 15per cent but, in the past, all the parties had been co-operative.
"We're all praying for rain and inflows that would allow us to review the reduction, but it is in force until further notice when we're confident the inflows are going to compensate for that loss," Mr Snow said.
A spokesman for Government House said it would comply with the request as it had done previously.
"We do not anticipate it will have any significant effect in the short term, and if it continues for a protracted period we will enact our zoned watering plan, to limit watering in some of the more non-critical parts of the property," he said.
Australian National Botanic Gardens general manager Peter Byron said it would follow suit.
"We already make every effort to minimise water use, with a high-tech irrigation system, moisture probes and heavy mulching," Mr Byron said.
"Our horticulturalists are reviewing their options should Canberra's hot dry weather continue, as we are reluctant to use Canberra's drinking water to care for our living collection."
A Territory and Municipal Services spokesman said Yarralumla Nursery's irrigation system would be altered to account for the water reduction, something that happened routinely to account for seasonal changes.
Water taken from the lake to irrigate Weston Park and Black Mountain peninsula was already below the allowable limit.
"As the water usage is already low, it is possible there will be no effect on either area. Water usage in these areas is being monitored closely," the TAMS spokesman said.
Water from the lake was also used to water trees around central Canberra, including in the city.
"The effect on urban tree watering should be minimal as there are other available sources of non-potable of water in the region," he said. The 15per cent reduction is being applied on a monthly pro-rata basis according to annual usage.
Annually, the National Capital Authority extracts 218 megalitres of water from the lake, the Australian National Botanic Gardens 170 megalitres, TAMS including the Yarralumla Nursery 149 megalitres and Government House 86 megalitres.
The level of the lake was important to the authority because it had responsibility for managing the lake "in a sustainable manner to protect its ecology and national significance" but wherever possible it is able to use the water as a "source of second-class water for irrigation purposes", Mr Snow said.