A perfectly sensible question I have been asked many times over the years – a source of fascination for tourists and necessary knowledge for locals. So I thought I’d give a simple explanation here. Enjoy.Prior to European settlement, the landscape was in balance. The district was fully vegetated, mainly with woodlands. When it rained, the native plants drank the majority of the water that fell – their deep roots capturing most of it before it reached the groundwater table deep below. A small amount, around 5% of rain, ran off to the creeks and lakes. Local waterbodies such as Police Pools, Lake Ewlyamartup and the Carrolup River were fresh, and an important source of water for Aboriginal people and early settlers.
When the land was cleared for agriculture, most of those deep rooted trees and shrubs were gone. In fact, 92% of Katanning’s land surface was cleared (why such extensive clearing took place is another story entirely). Now, when rain falls, it soaks into the ground and keeps going right down to the groundwater table with no deep roots to intercept it. Imagine a bath tub with the plug in and the tap on. It fills up. And that’s what started happening to the groundwater – it rose up and up, bringing with it salts that have been held in the soil profile for millennia.
The groundwater fills up like a bathtub
Eventually the groundwater filled up enough to reach the surface in the low-lying areas- the valley floors, the creeklines and the lakes. Salt was now at the surface, and the soil here waterlogged with the groundwater. The plants growing in these low-lying areas – both native bush and agricultural pasture and crops – simply can’t survive anymore and die, leaving bare smelly areas exposed. Waterbodies turned saltier than the ocean.
Woodland + salinity = death
But it’s not all doom and gloom. Farmers, researchers and Landcarers are an innovative, hardworking lot. With a three-pronged approach, techniques were trialled, tweaked and implemented. Some techniques moved away the pooled backlog of water in the low country. Some techniques intercepted rainwater before it could reach the groundwater table in the first place. Some techniques found plants that could grow in saline conditions, bringing life back to these patches.
Saltbush planted on saline land, bringing life and productivity back.
The spread of salinity appears to be slowing in Katanning. A patch of saltland can now be considered an important part of a farmers grazing system if set up right, where it was once a scourge. Communities are acting to reduce salinity in waterways. We have a better understanding of what does and doesn’t work.But the war is a long way from over. Farmers, in particular, continue to work to implement these strategies, but they can’t do it alone. It’s costly and time consuming work. Donate to Katanning Landcare today to help us help them to stop the salt.