Managing Yass Valley’s water supply during the drought

Water sustainability, security and supply issues present ongoing challenges to Councils as the nation continues to be gripped by drought.

The Yass Valley has experienced significantly below average rainfall, but is fortunately faring better than other parts of the state with the Yass Dam sitting at approximately 97 per cent capacity or just below the top of the dam wall.

The impact of water usage on the dam’s level is constantly monitored by Council staff. If there is no rainfall in the dam catchment between now and February 2020, the Yass Dam level is projected to reach about 80 per cent (an estimate based on current unrestricted use). At a level of 80 per cent, Council will consider imposing Level One water restrictions to address the risk to water supply that a long term drought poses. In preparation for this event, a draft Water Supply Restrictions Policy has been placed on public exhibition and can be viewed here. 

Level Four water restrictions are not expected to be enacted until the dam level drops to around 53 per cent of its total capacity, a point not anticipated for some time. While Council could impose Level One water restrictions now, there is currently no empirical basis on which to make that decision.

The standpipe operated by Council continues to supply a diverse group of water users such as famers, emergency services, businesses and Council projects. Council is in the fortunate position to be able to provide this service due to its decision to increase the Yass Dam wall by three metres, which increased its storage capacity to 2,460 ML, in 2013. Council has recently been made aware that one of those users - the Bango Wind Farm construction project – now has an alternate water source and is currently not buying water from the standpipe.

The prolonged lack of rain is having a considerable impact on Council’s road network, especially on our unsealed roads. Maintenance grading is best done when the gravel has the right amount of moisture. Grading during hot and dry periods is usually undertaken only to improve the running surface but this is not good for the long term integrity of the roads.

Sourcing water from the dam itself is not the issue, said Yass Valley Council Director of Engineering Stan Robb.

“Grading of unsealed roads requires not only water during the grading process, but follow up water on the road to continue the compaction of the material through vehicle movement,” explained Mr Robb.

“Without follow up rainfall, damage will be caused to the road surface that cannot be undone until it rains again. Without access to water close to construction and maintenance activities, works are generally required to cease until that water arrives.

“Accessing water solely from the Yass Dam (via the standpipe) requires significant turnaround time for water trucks and increased numbers of water trucks for each project. Aside from the high costs, it is the follow up water (or lack thereof) that creates the biggest issue around road surface integrity,” Mr Robb said.

As a result, Council will continue to maintain its unsealed road network through targeted repairs until weather conditions allow grading of the unsealed road network to be achieved in a sustainable way that is not detrimental to the road surface. The decision to temporarily cease the grading program for unsealed roads is one way in which Council can contribute to the conservation of our water supply.

Without continued rainfall, many rural roads will be subject to high dust generation from vehicle traffic, especially those travelling at high speeds. Major contributors to dust are vehicle volume, weight and, in particular, speed so driving at slower speeds will also help minimise these effects.

Submissions on the Draft Water Supply Restrictions Policy will be received by Council until 5pm on Tuesday, 31 December.

18 December 2019

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