The Keep River is approximately 9 km east of the Western Australia/Northern Territory border, to the east of the Kimberley region, between the Ord and Victoria Rivers. In addition to the Keep River, Sandy Creek drains the easternmost fringes of the Keep River Plain. Both the Keep River and Sandy Creek discharge into Joseph Bonaparte Gulf. Nearly all rivers and streams in the region flow only in the wet season. Permanent water is therefore restricted to sheltered pools and billabongs that retain water during the dry season, and the tidal reaches near the river mouths. Pools and springs are important refuge areas for fauna in an otherwise seasonally dry environment. Wet-season flows in all rivers and streams typically have high turbidity levels reflecting high sediment loads.
The Keep River rises south-east of Kununurra and has a catchment of some 5,000 km². The headwaters of the Keep River begin just south of the Victoria Highway. After passing through the gorges and low hills of the Keep River National Park, the river emerges on to the plains and flows north and then north-east to drain into the Joseph Bonaparte Gulf. Major tributaries of the Keep River include Knox Creek, Border Creek and Oakes Creek, which have the majority of their catchments within Western Australia.
Downstream the Keep River becomes a series of permanent waterholes separated by rock bars. At the confluence with Border Creek the river opens into a tidal waterbody some 50-100 m wide, which is connected to the Keep River mouth. Oakes Creek discharges into the Keep River in this reach, which becomes progressively wider and tidal to the river mouth. The tidal range at the mouth is approximately 8 m. A number of billabongs and lagoons occur on the floodplain of the Keep River, particularly within former drainage lines or anabranches of the river.
During the wet season the salinity levels in the non-tidal sections of the Keep River are generally less than 200 mS/cm. During the dry season higher salinity levels (up to 740 mS/cm) have been recorded in pools upstream of Legune Road crossing, indicating the effect of evaporation on this water-quality parameter. Salinity levels in the Keep River become progressively higher closer to the river mouth as the tidal influences become more substantial.
Interbasin water transfer occurs via the irrigation water distribution system, from the Ord River basin into the Keep River basin. Potential therefore exists for the transfer of aquatic invertebrates or other biota, via the irrigation water, from the Ord River to the Keep River.
Sandy Creek flows into the Keep River estuary. The catchment of Sandy Creek, which has an area of 1,240 km², lies entirely within the Northern Territory. Sandy Creek is immediately east of the Keep River Plain. At this location its bed is relatively wide and sandy containing sand beds 100 m and 200 m in width both downstream and upstream of Legune Road. Small semi-permanent lagoons or billabongs and sandy strips occur close to the creek. These are primarily associated with old meanders and are most apparent in the vicinity of Legune Road. Sandy Creek becomes tidal approximately 10 km downstream of the Legune Road.
The Weaber Plain is relatively flat and large parts are subject to inundation during the wet season. A number of intermittent watercourses from the surrounding hills, including Cockatoo Creek, Gum Creek and Melon Creek, discharge on to the plain. This water spreads out into indistinct sheet flow as the greater part of the plain has no incised channel. Only at the northern extremity of the plain is there defined drainage, and here Border Creek carries water eastwards into the Keep River. However, relatively little runoff reaches Border Creek except in very wet periods. The Pincombe and Cave Spring ranges to the south of the Weaber Plain produce runoff that is generally lost by infiltration or evaporation on the Weaber Plain, with little runoff reaching Border Creek.
Knox Creek enters the Keep River some 13 km upstream of the Legune Road crossing. The major tributary of Knox Creek is Eight Mile Creek, which rises just south of the Victoria Highway in the vicinity of Matheson Ridge. An unnamed major tributary of Knox Creek drains Mt Cecil and Abney Hill immediately north of Mirima National Park. The main drainage line of Knox Creek runs within a kilometre south-west of the Pincombe Range before turning east to the Keep River confluence in the vicinity of the border between Western Australia and the Northern Territory. The Knox Creek Plain is mostly well drained due to its uniform but gentle slope.
The fish fauna of the Keep River is diverse and numerous. Twenty-five species of freshwater fish were recorded from the Keep River and Sandy Creek areas by Helen Larson in 1998 and an additional fourteen species have been recorded as occurring in past surveys. No introduced fish species were recorded.
Ambassis mulleri - Muller's Glassfish
Amniataba percoides - Banded Grunter
Amoya sp. - Amoy Goby
Anodontiglanis dahli - Toothless Catfish
Arius graeffei - Blue Catfish
Arius leptaspis - Salmon Catfish
Arius midgleyi - Midgley's Catfish
Craterocephalus stercusmuscarum - Fly-specked Hardyhead
Eleutheronema tetradactylum - Four-finger Threadfin
Glossamia aprion - Mouth Almighty
Glossogobius aureus - Golden Goby
Hephaestus jenkinsi - Jenkins' Grunter
Lates calcarifer - Barramundi
Leiopotherapon unicolor - Spangled Grunter
Liza cf alata - Diamond Mullet
Liza tade - Flathead Mullet
Megalops cyprinoides - Ox-eye Herring
Melanotaenia nigrans - Black-banded Rainbowfish
Melanotaenia australis - Red-tailed Rainbowfish
Mogurnda mogurnda - Purple-spotted Gudgeon
Nematalosa erebi - Bony Bream
Neosilurus ater - Black Catfish
Neosilurus hyrtlii - Hyrtl's Catfish
Oxuderces wirzi - Peacock Mudskipper
Oxyeleotris selheimi - Black-banded Gudgeon
Parambassis gulliveri - Giant Glassfish
Periophthalmus argentilineatus - Silver-lined Mudskipper
Porochilus rendahli - Rendahl's Catfish
Pristis clavata - Dwarf Sawfish
Pristis microdon - Freshwater Sawfish
Rhinomugil nasutus - Pop-eye Mullet
Strongylura kreffti - Freshwater Longtom
Terapon jarbua - Targetfish
Thryssa brevicauda - Short-tail Thryssa
Toxotes chatareus - Spotted Archerfish
Two species of sawfish have been recorded in the Keep River - Dwarf Sawfish (Pristis clavata) and Freshwater Sawfish (Pristis microdon). The Dwarf Sawfish is coastal in distribution but can travel long distances up rivers into fresh water. Its conservation status is unknown but it may only occur in northern Australia. The Freshwater Sawfish is listed under the Commonwealth Endangered Species Protection Act 1992 as 'vulnerable', as well as being listed as 'Endangered' in the International Union for Conservation of Nature and Natural Resources (IUCN) Red List, and as 'Potentially threatened' in the 1998 Australian Society for Fish Biology's Threatened Fish List (1998). It is usually located in fresh water and in the upper reaches of estuaries, and may be isolated in small billabongs for several years until floods release it back into the estuary. It has been recorded from several rivers in Western Australia, the Northern Territory and Cape York Peninsula in Queensland.
Caridina spp. - Freshwater shrimps
Caridinides wilkinsi - Freshwater shrimp
Macrobrachium australiense - Australian river prawn
Macrobrachium bullatum - Northwest Australian river prawn
Macrobrachium rosenbergii - Giant river prawn
Macrobrachium tolmerum - East Australian river prawn
Austrothelphusa transversa - Freshwater Crab
Brachyachne tenella
Ceratopteris thalictroides
Chionachne cyathopoda
Echinochloa macrandra
Eleocharis aff. Brassii
Eleocharis sphacelata
Eleocharis spiralis
Fimbristylis blakei
Hydrilla verticillata
Ipomoea aquatica
Lygodium microphyllum
Marsilea mutica
Myriophyllum trachycarpum
Myriophyllum verrucosum
Najas graminea
Najas melesiana
|
Najas tenuifolia
Nymphaea hastifolia
Nymphaea violacea
Nymphoides indica
Pandanus aquaticus
Pandanus spiralis
Potamogeton tricarinatus
Tacca leontopetaloides
Typha domingensis
Utricularia gibba
Utricularia muelleri
Utricularia stellaris
Vallisneria annua
Vallisneria nana
Introduced:
Salvinia molesta
|
© Copyright Adrian R. Tappin
Created July, 2003
Updated 24 May, 2005
|
