Dalyup River and Coobidge Creek
Four sites were sampled on the the Dalyup River and two on Coobidge Creek; they are shown on the map above. Photographs are available for each site:
| DAL01 | DAL02 | DAL03 | DAL04 | COO01 | COO02 |
Background
The Dalyup and West Dalyup rivers drain in a southerly direction into Lake Gore. The main Dalyup River system flows for approximately 54 kilometres from the township of Scaddan, through the districts of Gibson and Dalyup to Lake Gore. The West Dalyup River, a major tributary of the Dalyup River, flows 45 kilometres before meeting the Dalyup River 8 kilometres upstream of Lake Gore. The Dalyup River is privately-owned, except for a section from Lake Gore to the junction of Dalyup and West Dalyup rivers, that is vested with the Department of Land Administration as Unallocated Crown landThe Dalyup and West Dalyup rivers formed thirty million years ago (during the Oligocene period) when the Darling Plateau uplifted and the southern coastline tilted toward the south to form the Ravensthorpe Ramp. This partly rejuvenated the rivers and they started to drain in a southerly direction instead of the previous east-west direction. Over time the rivers etched the weathered profile and sandplain, exposing granite along the bottom of drainage lines and left remnant Tertiary sedimentary rock with lateritic profiles exposed on the flanks of low hills.
The Dalyup River is the primary source of water supply to Lake Gore. The Dalyup River is an ephemeral system that flows mainly after winter rains. Summer flows are generally due to groundwater influxes from the surrounding land. The river consists of numerous pools that form important wildlife habitat during summer months. These river pools then join during the winter months as the rain begins to fill the low-flow channel.
Coobidge creek flows into an unnamed swamp near Lake Kubitch, which is linked with nearby Lakes Carbul and Gidong by a network of shallow swamps. These lakes are part of the Lake Gore Nature Reserve, which has recently been added to the international list of RAMSAR wetlands. In flood years water from this system is said to flow over an undefined path through several swamps and flow out to sea through Barkers Inlet to the west of the Lake Nature Reserve.
There is a chain of wetlands associated with the mid-upper section of Coobidge Creek contained within a large block of remnant vegetation. This chain of salt lakes appears to have formed in a diagonal line WNW-ESE and is possibly the remnant of a sediment filled ancient watercourse. The Coobidge Creek catchment draining into the wetland system is approximately 20700 hectares. Almost 20000 hectares of this area is cleared farmland, leaving less than 5% of the catchment with remnant vegetation. Annual rainfall is approximately 620mm at Esperance, with 410mm at Scaddan, 50km to the north.
Much of the above information was taken from the Rivercare website where more information is available.
Dalyup River and Coobidge Creek were sampled on 12th of September 2006.
Fish
Hardy heads and Gobies were found in these two systems. Pictures of these can be viewed in the gallery.River foreshore vegetation condition
The condition of the vegetation bordering the river at the sites sampled varied from near pristine to very disturbed with the better condition vegetation found along the Dalyup River system.Water Quality
Water samples were taken once from each site so while they help describe the water quality at the time of sampling they can not be used to explain the overall condition of the river for the rest of the time.The temperature of the water at the sites ranged from 15.33 to 17.26°C.
The lowest recorded salinity was on the lowest site on the Dalyup River at 23.32ppt. The highest was at site COO02 at 45.16ppt. The remaining sites had a similar salinity ranging from 30.93 to 38.36ppt which are around seawater which is about 35ppt.
Most of the sites had very acidic water with pH from 3.59 to 5.19. The exception was DAL01 with a pH of 8.04 which is slightly basic.
Total phosphorus recorded in the water at each site was similar and low ranging from 8 to 38 µg/L. Total nitrogen levels were higher and ranged from 1100 to 3000 µg/L.