Solar power future

Classic dolerite dyke: Great Eastern Highway near Mount Helena. 160 million year old black dolerite rock being squeezed up through the 2.8 billion year old grey granite when India separated from WA, creating a north-south ridge.
Classic dolerite dyke: Great Eastern Highway near Mount Helena. 160 million year old black dolerite rock being squeezed up through the 2.8 billion year old grey granite when India separated from WA, creating a north-south ridge.

With an endless supply of sunlight in towns like Northam and factories in China ramping up massive production of cheap photovoltaic panels of good quality, there is an area of opportunity opening for intensive agriculture in the Avon wheatbelt.

Traditionally, these types of farming were conducted on the Swan coastal plain from Bunbury to Lancelin because of the endless supply of fresh water at shallow depths. 

However, with the extreme pressure being put on coastal groundwater reserves and tight groundwater regulation, alternative areas are now being looked at as technologies becomes available.

The stand out technology is reverse osmosis (RO) which has been around since the 1950’s.

I believe in ten years you will see flourishing horticulture, aquaculture and floriculture farms in the Avon wheatbelt utilising previously unusable brackish groundwater from an endless supply of solar power.

Chris Davidson

The cost and efficiency of membranes has improved greatly in recent years, the single most game changer is a cheap endless supply of electricity from sunlight in areas like Northam.

Under the central wheatbelt there is a vast amount of brackish ground water, added to by land clearing in the past 150 years, which have sent groundwater levels high enough to seep out of the soil in low-lying areas and cause salinity issues with farming.

It could be said that this problem is a bonus for desalination as there is plenty of brackish water to process for farming.

To understand how to benefit from this technology you need to understand the natural history of the area. 

Natural history of area: 

Northam sits on the Yilgarn Craton which is a piece of continental crust that fused together about 2.8 billion years ago made mainly of granite.

Many people ask the question how did all the salt end up in the wheatbelt?

Well that is an interesting question, the source of this sea salt dates back millions if not billions of years ago long before the Indian ocean existed.

A lot of the salt in water flowing down the Avon river today, came from small grains of sea salt blown in on the winds from thousands of kilometres away from an ocean called the Tethys Ocean 160 million years ago and some from the newly formed Indian ocean.

The good news is that the salt levels in the wheatbelt since land clearing began have been draining to the Indian ocean at what could only be described as break neck speed and in four or five hundred years the salt that took billions of years to accumulate at current pace will mostly be returned to the earth’s oceans.

Large scale desalination plants like Kwinana and Binningup are built on the coast for one very good reason and that is once the sea water is separated you have fresh water and brine water. 

This brine water is then returned to the ocean with no impact, but inland desalination is a whole different ball game and disposing of the brine environmentally is where site selection is paramount.

There are a number of ways that the brine water can be disposed of, either by saline creeks or hyper saline dolerite dykes, both of which you need permission from the Department of Agriculture WA before commencement.

One of the best methods is by dolerite dyke, so what is a dyke and how are they formed?

What is a dyke?

Well most people don’t know that on the other side of Rottnest Island was once north east India 160 million years ago and the other side of Greenmount Hill is buried 15 km below Midland under the Swan coastal plain.

If you were there and you watch very closely from Greenmount Hill you would have witnessed the birth of the Indian ocean and the tremendous violent breakup that occurred between WA and India. 

You would have also witnessed the many tens of thousands of dolerite dykes being created throughout the Yilgarn Craton.

These dolerite dykes are many kilometres deep and many kilometres long, mostly hyper saline and confined, ideal for desalinating inland groundwater for small to medium scale agricultural systems without any impact to the environment. 

Dykes are sometimes located along ridges but not restricted to them, areas along Spencers Brook Road are classic examples of massive past geological activity looking at the North-South aligned ridges where you would find them.

The system at Misty Ridge Plant Farm in Wundowie that has been approved by the Department of Agriculture WA and construction about to start is going to be a 25,000 litres per day system which is up scalable running on solar power, re-injecting into a hyper saline dolerite dyke when completed.

I believe in ten years you will see flourishing horticulture, aquaculture and floriculture farms in the Avon wheatbelt utilising previously unusable brackish groundwater from an endless supply of solar power.

Chris Davidson

Misty Ridge Plant Farm