About Mound Springs
Mound springs are natural outlets for the waters of the Great Artesian Basin (GAB), where artesian pressure forces water to the surface. Most springs occur through fractures and faults on the margins of the Basin in the Far North of South Australia, north-western NSW and south-western Queensland. There are other springs further into the GAB, such as Dalhousie Springs in Far North South Australia, where water rises to the surface through geological fractures.
Most of the springs have only small flows or seepages, but one at Dalhousie has a daily output of around fourteen million litres per day.
The term mound springs reflects the characteristic mounds that have developed at many (but not all) of the springs. In some areas the mounds have been building for thousands of years. Spring flows were stronger in the geological past.
The precipitation of salts and minerals, along with the accumulation of wind-blown sediments from the surrounding country, has created the mounds.
The Great Artesian Basin
The Great Artesian Basin underlies 22% of Australia and is one of the largest groundwater basins in the world. The aquifers of the Basin can be up to 3,000 metres deep. With water moving laterally through the Basin at only one to three metres per annum, the waters are up to two million years old, but the Basin is also very complex with some sub basins having little or no current water movement.
Replenishment (recharge) of the GAB occurs mainly along the western slopes of the Great Dividing Range. There is also some minor recharge around the Basin’s south western margins in South Australia.
The recharge areas are elevated well above the Basin and the result is a pressurised system where the only natural outlet for the waters is via the mound springs and a more diffuse process known as vertical leakage.
The recharge areas are elevated well above the Basin and the result is a pressurised system where the only natural outlet for the waters is via the mound springs and a more diffuse process known as vertical leakage.