Water pushing up from the Great Artesian Basin finds cracks in the earth's surface and breaks though under pressure as natural springs. Some springs deposits salts and sediments, wind blown sand from the desert is added and over time a mound forms. Mound Springs are a key feature of the Oodnadatta Track region and there are literally hundreds of them scattered between Marree and Oodnadatta.
The sketch shows the classic shape of a mound spring. It is formed when artesian water leaks to the surface and evaporates away leaving dissolved salts behind. These salts accumulate rapidly and form a hard limestone "mound" that is often topped with moist soil, vegetation and perhaps a pool of permanent water.
Some mound springs such as the "Bubbler" in the Wabma Kadarbu Reserve have a very strong flow. Other such as the nearby Blache Cup have a gentle flow and form a larger mound. Have a look at nearby Hamilton Hill to the south. The hill is an extinct mound spring formed perhaps millions of years ago.
The Great Artesian Basin lies under nearly one fifth of Australia. Most of the water enters the basin in Queensland over 1000km away. The basin is up to 3km deep in places. Water flowing from the mound springs may have been in the basin for up to two million years.
Earthcache tasks. You will need to visit both The Bubbler and Blache Cup. Please forward your answers to the cache owner for verification.
Q1: Estimate the flow rate at each mound spring.
Q2: Propose a reason why the flow rates might be different.
Q3: In your opinion is the water?
...a) Salty
...b) Brackish
...c) Fresh
...d) Will make good tea.
Wabma Kadarbu Mound Springs Conservation Park is located 500 kilometres north of Port Augusta, access is via the Oodnadatta Track. The spring's entrance is about six kilometres south-east of Coward Springs. Vehicle access within the park is limited to the four kilometre long entrance road to Blanche Cup and The Bubbler mound springs.