Day 8 |
Apr 29, 2014


By Brad Climpson, Biologist
Coordinates: 15° 27.0’ S and 128° 06.0’ E
Weather: partly cloudy
Temperature: 25-34 degrees Celsius
Pressure: 1009 hPa
Wind: 0-5 knots

Arriving at the Wyndham jetty after steaming through the Cambridge Gulf during the morning Captain Luksa put Silver Discoverer alongside for the day’s activities. Wyndham, the oldest and most northerly town in the Kimberley region, would be the starting point for two wonderful tours planned for the day.

We climbed aboard our buses on the jetty and some of us headed out to Kununurra for our Ord River cruise -while the other groups headed for their scenic flight over Lake Argyle, the Argyle Diamond Mine and Purnululu National Park to see the world famous Bungle Bungle Ranges.

Triple J Tours were our hosts for the Ord River Cruise and upon arrival into Kununurra we boarded the Osprey, a river boat with a lot of horsepower, purpose-built for navigating the 55 kilometre stretch to the Ord River Dam Wall. Our guide Dylan began the tour explaining how much water was stored in the dam at any one time –it could fill Sydney Harbour 14 times when the dam is not even at full capacity. It has the ability to store 22 Sydney Harbours or 10,763,000 megalitres (a megalitre being 1,000,000 litres)!
Lake Argyle, the largest artificial lake in the southern hemisphere, has a 1000 km² surface area. The lake was formed when the Ord River Dam was completed in 1971 by the American Dravo Company. The dam is a clay-core dam that is covered by rocks from the surrounding area. It is built this way to allow for the movement of the land around it. This prevents cracking and thereby minimizes degradation of the dam’s structure.

The dam was created for the Ord River Irrigation Scheme which would allow for the irrigation of highly fertile soil in the surrounding areas -so crops could be grown. Today the most productive crops include Indian Sandalwood, Chia Seed and melons. By damming the Ord River a new ecosystem was formed as there is now a permanent body of water and flowing rivers in the area year-round. 26 species of native fish, as well as salt and fresh water crocodiles thrive in the area. There is thought to be 30,000 freshwater crocodiles in Lake Argyle itself. The permanent freshwater bodies have also attracted large numbers of birdlife to the area -including Magpie Geese, Bustards and White Headed Stilts. Lake Argyle and Lake Kununurra are recognised as RAMSAR protected wetlands and are considered Important Bird Areas (IBA’s).

The tour wound up the ever narrowing Lake Kununurra giving us wonderful vistas of the large sandstone cliffs that had experienced folding and cracking –similar to what we had seen in Yampi Sound and Talbot Bay further south on our trip. We stopped for a camp lunch at a beautiful spot on the side of the river. There we had our lunch under a covered seating area while Archerfish and Catfish swam around in the shallows nearby. After lunch we continued cruising whilst spotting Ospreys, White-bellied Sea Eagles, Black and Whistling Kites, Little Pied Cormorants, Jacana, Rainbow Bee-eaters and a number of other birds. At the end of our journey we were taken in to meet our bus once again -but not before a Freshwater Crocodile eyed us off as we made our way ashore.

After the cruise we visited the old Durack Homestead. It has been rebuilt in a new location due to the flooding of the valley covering the land it once occupied. Then it was time to take the bus back to Wyndham passing beautiful sandstone cliffs and Boab trees whilst the Black Kites soared overhead.

For all those taking the scenic flight for the morning, they were allocated their seats for the trip and then took off into the air either at Wyndham Airport or Kununurra airport. The journey would take everyone over the Argyle Diamond mine -which is productive due to the Halls Creek Fault line to its south. The mine is famous for its pink diamonds; however, the majority of the diamonds is not of high grade and is used for industrial purposes. Lake Argyle was also viewed from the air and its enormity could only be appreciated from this angle. The 1000 km² surface area of the lake was strewn with beautiful islands that were the result of mountains disappearing as the lake was filled, leaving only their peaks visible.

Perhaps the highlight of the trip for many was the view of the beehive like structures of the Bungle Bungle Ranges found in Purnululu National Park. The name Purnululu comes from the Kija people of the area and refers to the sandstone structures found here. The Bungle Bungle Ranges reach elevations of 578 metres. These wonderful structures have been formed from a plateau of sandstone being eroded away over millions of years. The special banding found in the structures is from layers of sandstone being laid down with layers of clay-rich sandstone in between them.
The clay-rich sandstone holds water more effectively and therefore cyanobacteria can grow on them -causing the dark lines we see. The orange banding is from the porous sandstone that dries very quickly and has oxidized, leaving a beautiful orange rust colour.

After the flights everyone returned to Wyndham and Silver Discoverer set off through the Cambridge Gulf out towards the Timor Sea for our crossing to Leti Island.