A release of water from Clarrie Hall Dam yesterday has failed to flush salt water from the Bray Park Weir, resulting in Tweed Shire Council asking all residents to minimise their use of water to limit the amount of salty water entering the Tweed reticulation system.
The council’s water manager Anthony Burnham said the water release from the dam had limited success.
‘The wave that went down the river yesterday evening prevented further salt water getting into the weir from another higher-than-predicted tide overnight,’ Mr Burnham said.
‘But the salt levels in the Bray Park Water Treatment Plant are higher than yesterday and more residents will have salty water in their taps today.
‘The salt concentration will spike shortly and then we will see a gradual decrease in the salinity over the coming days. So it is important that the residents work with us and limit their use of water to minimise the quantity of salty water being drawn into the system. Basically all the salty water drawn in will have to be released via household taps so the less drawn in, the quicker this situation can be resolved.’
A large release of water from Clarrie Hall Dam yesterday refreshed the top strata of water in the weir but the heavier salty water had sunk to the bottom of the pool.
‘Our tests have confirmed that the water being drawn into the Bray Park Treatment Plant is saltier than the water we tested yesterday morning,’ Mr Burnham said.
‘We have closed the deeper baffles where the water intake occurs to limit the draw of salt water from the lower water stratum within the weir pond and are only drawing from the top strata, which was refreshed by yesterday’s release from the dam.
‘Today we will begin a continual release from the dam of 50 megalitres a day to maintain that refresh as we bring in a dredge to draw the salty water from the bottom and pump it out directly over the weir wall.
‘However, the salty water already within the reticulation system is going to spread beyond Murwillumbah today and over the coming days.’
Tides up to 380mm higher than predicted pushed over the weir wall on Monday night.
‘Since Saturday, all the high tides have been greater than predicted but the last of these occurred overnight. While the spectacular solar eclipse in the northern hemisphere played a major role in Monday night’s overtopping, the fact is that with the effects of climate change and rising sea levels these events are going to become more frequent and of higher intensity.
‘This current incident brings into clear focus the need to raise the wall of the weir and council will be working hard to get the approvals and licences in place to get this important project off the drawing board and into construction.’
The Australian Drinking Guidelines advise that the salt levels are not harmful to human health. Residents are advised to use bottled water for drinking if the taste of the water is too unpalatable.
The water at Uki and Tyalgum is not affected and no restrictions apply in those villages.