The Yalgorup Lake System is unique in the world.
Formation of the Yalgorup Lake System
The Yalgorup Lake System was formed during the last rise in global temperatures 7,000 years ago. Rising sea levels and increasing ferocity of storms drove enormous waves onshore dumping massive loads of sand from the bottom of the ocean against the existing limestone shoreline. As the temperature dropped and the seas retreated three parallel lines of shallow salt lakes remained. These three lines were separated by sand dunes. The lakes were sinks with no inlet and no outlet. They were salt water residues with the salinity of the ocean from which they had formed.
The level of the lakes and the salinity of the water rose and fell during the course of the year due to evaporation over summer and recharge by rainwater in the winter.
Formation of an Underground fresh water aquifer
The rain fell also on the sand dunes and the limestone shoreline bordering the lakes. This rain soaked through the porous Quindalup sands onto the limestone bed rock and formed a lens of freshwater lying over the more dense salt water within the limestone. This fresh water became a shallow superficial aquifer which flowed beneath the salt lakes.
The fresh water, heavily impregnated with calcium carbonate, seeped into the lakes. This also affected the salinity of the water within the lakes. Some lakes with considerable underground seepage became hyposaline, less saline than sea water.
Why are they unique?
This section will be expanded in the future but in summary the following features are globally unique or significant:
- The complex nature of the most seaward barrier – globally unique
- The line of lakes and limestone ridges – globally unique
- The nature of the sedimentary fill in the lakes – globally unique
- The stromatolites – globally significant
(Brocx M, 2010)