Unwanted intrusion

While a salty rim on a margarita glass may be welcome, salt in our drinking water is definitely not!

But saltwater getting into our water supplies is a very real problem – one you need to know about.

Known as saltwater intrusion, it’s where saline (salty) water moves into freshwater aquifers – like our Yarragadee aquifer, which supplies our drinking water.

A bit of science to explain. Several hundred metres below surface level, groundwater is stored within the rocks, clay and sand within the aquifers. Rain seeps into the aquifers and slowly flows underground to the ocean, or returns to the surface as a catchment or other body of water before reaching the ocean. So there’s a point near the shore where the stored fresh water and salty ocean water meet – and that’s just the way it is, they have to meet at some point.

The problem is when the amount of water being drawn out of the ground by bores is more than the amount that is naturally replenished by rain, this causes the groundwater levels to drop and the salty water moves inland and mixes with the fresh groundwater. Suddenly, we’ve got salty drinking water.

A bit of salt can’t hurt right? Wrong! Fresh water contaminated with just five per cent of seawater makes it unusable. And not just for drinking, but for irrigating crops, parks, gardens and golf courses. It’s also bad news for groundwater dependent ecosystems.

Yarragadee and salination

Groundwater is extracted from the Yarragadee aquifer using a coastal bore network. The nine bores, which run between 150m to 700m in depth, draw the water from the aquifer. The water is then treated and pumped to homes and businesses.

The Yarragadee contains around 1,267,000GL of fresh groundwater, but this needs to be replenished by rainfall. The thing is, the amount of rain is declining thanks to climate change. Since 1970, the amount of rain has reduced by 10-20 per cent – and it’s expected to keep on falling. This means there will be less water available to replenish the aquifer.

The reduction in rainfall over the last 50 years is already having an impact on Yarragadee – saline water has already migrated into the aquifer. And it’s set to get worse.

The problem is made harder by the fact that some of our bore system is located near the coast – it’s too close to the sea and it’s slowing being impacted by saltwater intrusion. When first built, the bores were well-positioned to draw the fresh water needed. Fast-forward several decades and the positioning is not so great. Eventually the bores will start to draw saltier, unusable water. Within the next 50 years, the coastal bore network simply won’t be able to supply the same high-quality water it does today.

This is a big deal when you consider that all of Busselton’s drinking water is extracted from the Yarragadee aquifer. That’s right, all of our drinking water. Unlike Perth and other areas around the State, Busselton doesn’t currently have any alternative sources of drinking water.

What we’re doing about it

So salination is something we need to try to get on top of. And we are.

One of the main things Busselton Water is doing is developing new inland infrastructure. A new water treatment plant and inland bore network will help secure reliable drinking water supplies for the next 50 years and beyond.

Project pre-approvals and planning is underway for the new treatment plant, known as Plant 8, and the new bore (Bore 22). It will be built on a four-hectare site, approximately five kilometres from the coast, opposite the Busselton Margaret River Airport.

The new bore field will not only produce its own water but also reduce abstraction from the existing coastal bores – allowing them to have a longer life.

The inland bore network is just one of the ways we’re planning for the future. We’re also exploring innovative technologies and sustainable practices to safeguard water supplies. And encouraging waterwise behaviours right across our community. This is where you come in.

Play your part

We’re planning to make sure we have Water for Tomorrow, but you need to do your bit too. More infrastructure and other initiatives will help secure drinking water supplies, but we’ll all need to use water wisely.

Check out our tips and tricks to help you save water. And if you want to find out more about Water for Tomorrow, head to our webpage.