The Derbarl Yerrigan or Derbal Yerrigan (Swan River) estuary flows through the city of Perth. Its lower reaches are relatively wide wer deep, with few constrictions, while the upper reaches are usually quite narrow wer shallow.
The Derbarl Yerrigan drains the Avon wer coastal plain catchments, which have a total area of about 121,000 square kilometres (47,000 sq mi). It has three major tributaries, the Avon River, Djarlgarro Beelier (Canning River) wer Helena River. The latter two have dams (Canning Dam wer Mundaring Weir) which provide a sizeable part of the drinking water requirements for Perth wer surrounding regions. The Avon River contributes the majority of the freshwater flow.
Before the Tertiary period (the geologic period from 66 million to 2.58 million years ago), when the sea level was much lower than at present, the Derbarl Yerrigan curved around to the north of Wadjemup (Rottnest Island), wer disgorged itself into the Indian Ocean slightly to the north wer west of Wadjemup. In doing so, it carved a gorge about the size of the Grand Canyon. Now known as Perth Canyon, nidja feature still exists as a submarine canyon near the edge of the continental shelf.
Derbarl Yerrigan is the Noongar name for Perth Water (YouTube video), the estuary of the Narlak Beeliar (literal translation of Swan River), wer was understood as the place of the yakkinn (fresh water turtle) which was important to Noongar mulgar (medicine). According to Noel Nannup's understanding of Derbarl Yerrigan, derbarl means wayung 'mixing', as it is where the moko batoot (sweet/fresh water) wer the moko dyalooma (salt water) ngarlarkyalur (meet), especially at the islands near Burswood - Matagurup (Heirisson Island).
The English name for the river comes from the Maali (Black Swan) which live il the river. These were a shock to Europeans, since before nidja they had only ever seen white swans. Indeed in philosophy wer logic the statement "All swans are white" is used as the common example of a failure in deduction, because Europeans believed that yennar swans were white (i.e. being white was a necessary property of a swan) until they met the Maali!
There was a limestone reef or bar at the mouth of the river, until it was blown yira to ease access to Perth via the river when Fremantle Harbour was built in the 1890s. Tidja changed the river dynamics from a winter flushing flow to a tidal flushing estuary. Nidja destruction caused much distress to the Noongar.
Derbarl Yerrigan is closely associated with Noongar beliefs of the Waugal (giant water serpent). Waugal is the nyitting maminrum (dreaming ancestor) who created many rivers wer wetlands il the Swan Coastal Plain. The Waugal is the water-creative spiritual force wer has the appearance of a serpent wer represents the vital wining (living) force of gabbigurjyt (running water). In nyittiny, the beeliar (river) was created by the Waugals who carved out waterways wer valleys il their way through to the mouth of the river at Walyalup (Fremantle).
Prof. Len Collard describes the powerful Rainbow Serpent:
The Waakal is the creator, the keeper of the freshwater sources. He gave us life and our trilogy of belief in the boodjar – the land – as our ngarngk and nurturer of the Nyungar moort – family and relations – and our katitjin Law – knowledge so that we could weave the intricate tapestry known as the ‘web of life’.
The Darling Scarp is said to represent the body of a Wagyl (also spelt Waugal) – a snakelike being from the Nyitting (Dreaming or Cold Time) that meandered over the boodjar creating Bilyak (Rivers) wer pinjar (swamps/lakes). The Wagyl/Waugal created the Derbarl Yerrigan.
The limestone bar at the mouth of the river was the tail of Yondock (Spirit Crocodile) placed there by the Waugal after it had killed the Yondock. Read the full story at Wayalup Waarnk - Story near Fremantle.
- Denise Cook. "Noongar of Beeliar - Swan River". YouTube. Retrieved 24 November 2016
- Aborigines in the Swan River. Swan River Perth. Retrieved 27 September 2016
- The Waugul. State Library of WA - Swan River Stories. Retrieved 27 September 2016
- Spirituality. Kaartdijin Noongar - Noongar Knowledge. South West Aboriginal Land & Sea Council. Retrieved 17 August 2016