Transcript
Chloe Warburton
Welcome to Talking Water with GMW, where we discuss all things water. In this episode, we're joined by GMW Groundwater and Streams manager Matthew Pethybridge, who takes us through how groundwater is managed in our region and the role it plays in water resources. We have episodes in a variety of topics, so be sure to give them a listen. You can find them on the GMW website or wherever you listen to your podcasts.
Chloe Warburton
Okay, so what is groundwater?
Matthew Pethybridge
What is groundwater? Well, it's often referred to as invisible water, so we can't see it, we can't touch it, so it's very different to surface water where we see it in our rivers and lakes, but there's actually large volumes of water below the surface in what is known as aquifers. So these aquifers are typically made up of gravel, sand, basalt or fractured rock, which water accumulates in. Water can move through these aquifers, through these materials, because they have large connected spaces that make them permeable.
The speed at which the groundwater flows depends on the size of the spaces in the sand and rock and how well the space is connected. So the water in these aqueduct can be brought to the surface naturally through a spring and can also be discharged into our lakes and streams and that gives us the base flow within some of these systems.
The groundwater can be extracted through a bore, which is drilled into the aquifer, which allows for irrigation or other uses. It makes up about 15% of Victoria's water needs.
Chloe Warburton
And what determines if there is groundwater in a certain location? How do we find it?
Matthew Pethybridge
Groundwater can actually become almost everywhere. So it's depends on the depth and the different aquifer geological systems. That aquifer has a water table which can be deep or shallow and it might rise or fall depending on many factors. This can be dependent on heavy rains, snow melt, may cause the water table to rise or fall and heavy pumping through irrigation and other uses can also have an impact on that water table and allow it to fall.
But it does recharge most years. Groundwater supplies replenish through rain and surface water that seeps down through cracks and crevices beneath the surface. To locate groundwater accurately and determine the depth, quantity and quality of the water there are a number of techniques that can be used. It is important to take into account the hydrologic and geological features within the planning and management of this resource.
So there are many techniques, the general techniques include investigating bore drilling, so we drill small bores to see what depth the groundwater aquifers are. We have a groundwater map, so we have a great understanding of where aquifers are and we can provide information. There is test pumping, which gives us an understanding of how much water is down there and how much can be extracted. And we also have the hydrogeological understanding of geological formations which develop these aquifers.
Across northern Victoria, we have the State Observation More Network, which is made up of both 1200 observation bores, and for around about 400 of these we have real time monitoring, which gives us a great understanding of what's impacting our groundwater aquifers, is it pumping, is it rainfall, and that connection between streams and the groundwater aquifer systems.
Chloe Warburton
And what's and role when it comes to managing groundwater?
Matthew Pethybridge
So we've played a central role in the sustainable management of ground with a for local communities and environment. We employ a number of groundwater experts who have great understanding of how groundwater works and how moves. In doing this we administer groundwater licenses and develop and implement management plans on behalf of the Water Minister. These groundwater management plans place a limit on how much groundwater can be sustainably licensed for extraction and trading rules for the movement of groundwater and we also have an allocation network for when levels start to fall to low
Licensed groundwater extraction is measured with a water meter, at least annually, to ensure license holders are compliant with the license conditions. So we actively monitor to make sure that they are compliant and that how much they're taking is within the license. GMW updates its website with groundwater levels, which are of interest to allow users and the public to easily access this information and see the health of their aquifers within their own areas.
GMW also publish annual newsletters for each water management area with general information about groundwater levels, how much water was used by people with licenses to extract it. These also provide hydrographics and also trading information to give you an idea of the trading market within each of those areas.
Chloe Warburton
And what are some of the things that groundwater is used for in our region?
Matthew Pethybridge
Groundwater supports a significant amount of agricultural activity, commercial operations, and is an essential source of water for domestic and stock supply, which is a private right. We have several urban water holders who provide town water through groundwater also. So we have around about 50 towns across Victoria, which are either partially completely reliant on groundwater as a main source of drinking water.
For example, northern Victoria towns like Bright and Daylesford use groundwater for their urban water drinking. It's also an important environmental asset that provides base flow to streams and supports wetlands and other groundwater dependent ecosystems.
Chloe Warburton
So how is our understanding and use of groundwater changed in recent years?
Matthew Pethybridge
Terms of groundwater has significantly advanced since the millenium drought, with groundwater being recognised as important resource. Groundwater mapping and modeling and our extensive monitoring network has provided us with a greater understanding of that long term sustainability and future climate impacts. Groundwater is becoming increasingly precious, with challenges emerging for the long term security of water supplies. So it's no longer the secondary resource within our systems, it's part of our ongoing resource for all water users.
Chloe Warburton
And what's groundwater like in terms of water quality?
Matthew Pethybridge
The groundwater quality within our aquifers varies from fresh drinking water to saltier than seawater. Water quality of groundwater depends on a number of different factors. It can be affected by the source aquifer. So, for example, the aquifer could be found with marine sediments which have naturally salty occurrences from being former seabeds. We have agricultural runoffs, so high nutrient loads that go into our aquifer systems. Other factors that impact on water quality can be pollution, flooding which goes across our flood plains and seeps into our aquifer systems. We have seepage from rubbish tips, and we work with the Environment Protection Agency to manage that to a solution. And we also have contaminated surface waters so that can bring that high nutrients and other nasties into the system.
Other factors can actually be naturally occurring. This can be naturally occurring chemicals within a geological aquifers, but also radioactive substances. So a great example of this is our mineral springs in northern Victoria, which have a natural radioactive substance within them. In the towns where groundwater is used as a source of drinking water. The water is treated to make sure it's fit for purpose.
Chloe Warburton
And how does GMW manage groundwater so that is fairly distributed as a resource?
Matthew Pethybridge
So managing how groundwater can be accessed is a foundation of sustainable management. GMW employs groundwater specialists to ensure this long term management of the resource. before grain was used from a board other than for a domestic stock eight works license and take and use license are required for these licenses. They're issued to protect the rights of the current license holders, ensure the water is shared among all users, and all the environmental requirements are protected.
After GMW receives an application for take and use license, a site inspection occurs to collect information about the application. This is taken to identify nearby bores, waterways or important environmental features that may be impacted. Following the site inspection, an assessment of the risk of impacts to groundwater users or the environment is undertaken. This assessment is done in accordance with the Victorian Water Act and relevant management plans.
These relevant management plans are designed specifically for those different geological environments that we have across northern Victoria. If risks are identified, an application may be refused, an application may be amended - so changing volume of water required or the extraction rate. Or we can also request that the applicant engage a qualified hydrogeologist to provide evidence that the risk is minimal. So the idea that either employing an expert in the field who has a greater understanding of the environment at sort of our knowledge that we have at GMW.
And of course any submissions to an application which were received, they are considered as part of this process. So submissions are providing extra information which allows us to assess the impacts of the application.
Chloe Warburton
Fantastic. And if people want more information on groundwater, can they just go to our website, the GMW website?
Matthew Pethybridge
Our website is best place to start. It's got information for all our different groundwater management areas and just general information on what is groundwater and what do I have to do to access it.
Chloe Warburton
Fantastic. Thank you so much for your time, Matt.
Matthew Pethybridge
Thanks Chloe.