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The Ord River is situated in the east Kimberley region of Western Australia and extends into north-western Northern Territory. It rises near Halls Creek and has a catchment area of some 64,000 km². It is approximately 650 km long and flows via Lake Argyle and the Kununurra Diversion Dam (Lake Kununurra) on route to the Cambridge Gulf near Wyndham. The major tributaries of the Ord River are the Panton, Elvire, Nicholson, Negri, Wilson / Bow and Dunham Rivers. Lower Ord River Tributaries include Valentine Creek, Spring Creek, Goose Hill Creek, Parry Creek and Reedy Creek. The eastern most tributaries extend over the State border into the Northern Territory.
The Ord River catchment has a semi-arid to arid monsoonal climate with two distinct seasons: a warm, dry season; and a hot wet season occurring from November to April. Much of the wet season rain is the result of localised thunderstorms but cyclonic disturbances are common, particularly during January and February, and can degenerate into tropical lows bringing heavy rainfall within a short period. Most of the annual rainfall is the result of the monsoonal depressions and tropical cyclones. Rainfall can be infrequent for the remainder of the year with several consecutive dry months not uncommon. Temperatures during the day are high throughout the year, but particularly during the wet season, when maximums above 40°C are frequent.
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| Elvire River |
The first detailed records of the East Kimberley were made by Alexander Forrest during his 1875-79 expedition. After Forrest's expedition, flocks of sheep and cattle were moved into the region to create pastoral stations in 1884-85 when the Buchanan, Durack and McDonald families moved to the district primarily from Queensland.
The discovery of gold at Halls Creek around 1885 and more substantially in southern Western Australia in the 1890s, created a dependable market for meat, and cattle grazing soon became a dominant part of the local economy. The town of Wyndham was gazetted in 1886. By 1920, cattle numbers in the Kimberley had risen to over 500,000. Thereafter, however, the cattle population has remained virtually static and is now in decline.
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| Lake Argyle |
The Ord River has twice been dammed for agricultural irrigation. In 1963, the low altitude, 20-m high Lake Kununurra Diversion Dam was established about 70 km upstream of the tidal limit. About a decade later, the much larger Ord River Dam was completed a further 55 km upstream to form Lake Argyle. The section of the Ord River between these two dams is Lake Kununurra. Including the tributaries and associated perennial swamps and lagoons, the lake has a full supply surface area of around 100 million m².
The Ord River irrigation development has resulted in the transfer of water, via the irrigation water distribution system, from the Ord River catchment into the Keep River catchment. Potential therefore exists for the transfer of aquatic flora and fauna, via the irrigation water, from the Ord River to the Keep River. Prior to the construction of the dams, the Ord would have had a highly seasonal flow with large summer flood events and little or no flow during winter. The floodplain would have been extensively inundated by the flood events. In the dry season, the river would have dried to a series of isolated pools in the deeper parts of the channel. The large tidal range within Cambridge Gulf would have resulted in saltwater intrusion well up the channel during the dry season. The tidal influence would still have been significant in the wet season, but during the very large flows the saline interface would have been well downstream, probably into the Cambridge Gulf.
River regulation since dam construction has resulted in perennial flow downstream of Lake Argyle. Consequently there have been substantial changes in river dynamics, sediment transport, channel morphology, biodiversity, and riparian vegetation. The Lower Ord is now currently evolving to suit its new flow conditions, a process which will continue for many years. The implications of these changes to the fish fauna are likely to be profound and include loss of habitat diversity and reduced species diversity, carrying capacity and population size of the species.
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| Craterocephalus stramineus - photo© Günther Schmida |
The Ord Basin includes the Ord, King, Pentecost, Durack, Forrest, Lyne, and Helby Rivers, Parry Creek and the False Mouths of the Ord entering the Cambridge Gulf. There is probably a high degree of genetic interchange in fish between these places, preventing geographic speciation between rivers. Many fish species are migratory and euryhaline. Major escarpment waterfall barriers are lacking on the Ord River. (These barriers are probably responsible for the high degree of fish speciation and hence endemism in other Kimberley coastal rivers to the west). During major flood events inner gulf tidal waters become nearly fresh for long periods.
Ambassis agassizii - Agassiz's glassfish
Ambassis macleayi - Macleay's glassfish
Ambassis sp. - Northwest glassfish
Amniataba percoides - Barred grunter
Anguilla bicolor - Northern eel
Anodontiglanis dahli - Toothless catfish
Argyrosomus sp. - Mulloway
Arius graeffei - Lesser salmon catfish
Arius leptaspis - Triangular shield catfish
Arius midgleyi - Silver catfish
Arrhamphus sclerolepis - Snub-nosed garfish
Aseraggodes klunzingeri - Tailed sole
Carcharhinus amboinensis - Pig-eye Shark
Carcharhinus leucas - Bull shark
Craterocephalus stercusmuscarum - Flyspeck Hardyhead
Craterocephalus stramineus - Blackmast
Elops australis - Giant herring
Glossamia aprion aprion - Mouth almighty
Glossogobius giuris - Flathead goby
Glossogobius sp.2 - Square blotch goby
Hephaestus jenkinsi - Jenkins grunter
Himantura chaophraya - Freshwater whipray
Hypseleotris compressa - Empire gudgeon
Lates calcarifer - Barramundi
Leiognathus equulus - Ponyfish
Leiopotherapon unicolor - Spangled perch
Liza cf alata - Ord River mullet
Lutjanus argentimaculatus - Mangrove jack
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| Kurtus gulliveri - photo© Günther Schmida |
Kurtus gulliveri - Nurseryfish
Marilyna meraukensis - Merauke toadfish
Megalops cyprinoides - Oxeye herring
Melanotaenia australis - Western rainbowfish
Mogurnda mogurnda - Northern trout gudgeon
Nematalosa erebi - Bony bream
Neosilurus ater - Black catfish
Neosilurus hyrtlii - Hyrtl's catfish
Neosilurus pseudospinosus - False-spined catfish
Nibea squamosa - Scaly Croaker
Oxyeleotris lineolata - Sleepy cod
Oxyeleotris selheimi - Giant gudgeon
Parambassis gulliveri - Giant glassfish
Polydactylus sp. - Threadfin salmon
Porochilus rendahli - Rendahl's catfish
Pristis microdon - Freshwater sawfish
Scatophagus argus - Spotted scat
Strongylura krefftii - Freshwater longtom
Syncomistes butleri - Butler's grunter
Syncomistes kimberleyensis - Kimberley grunter
Thryssa sp. - Anchovy
Toxotes chatareus - Seven-spot archerfish
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| Syncomistes kimberleyensis - photo© Günther Schmida |
Caridina longirostris - Longbeak caridina
Caridina nilotica - Common caridina
Caridina serratirostris - Spiny-beaked caridina
Macrobrachium australiense - Australian river prawn
Macrobrachium bullatum - Northwest Australian river prawn
Macrobrachium rosenbergii - Giant river prawn
As for most of the Australia's rivers and wetlands, there is a very large gap in our knowledge of what plant species are present and their distribution. Many river systems in the Kimberley region have not been adequately surveyed for aquatic plants. Only minor surveys have occurred and there are some river systems that have had no surveys at all. Even those catchments which have been surveyed have had limited sampling and particular habitat areas within these rivers have been under-represented in the surveys. However, the following species have been reported.
Ceratopteris thalictroides, Hydrilla verticillata, Ipomoea diamantinensis, Marsilea mutica, Myriophyllum callitrichoides subsp. striatum, Myriophyllum costatum, Myriophyllum trachycarpum, Myriophyllum verrucosum, Najas graminea, Najas melesiana, Najas tenuifolia, Nymphaea hastifolia, Nymphaea violacea, Nymphoides indica, Persicaria attenuata, Phragmites australis, Phragmites karka, Potamogeton tricarinatus, Tacca leontopetaloides, Typha domingensis, Typha orientalis, Utricularia gibba, Utricularia muelleri, Utricularia stellaris, Vallisneria annua, Vallisneria nana and Wolffia angusta.
© Copyright Adrian R. Tappin
Created July, 2005
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