Current Musing: Murray and Darling River Systems (On hold - COVID-19)
Sunrise at Balonne River

Lachlan River

The Lachlan River is considered to be the fourth longest river in Australia. Its source is on the Breadalbane Plain near Goulburn, on the Great Dividing Range. From here it flows westwards out onto the fertile plains of the Riverina and onto the semi-arid woodlands. The river ends at the Great Cumbung Swamp. Water will only reach the Murrumbidgee River during large floods.

I used the phrase "considered to be the fourth longest river" based on the approximations provided by GeoAustralia, but from my own analysis it closely ties with the third placed Darling River. Tracing satellite images in QGIS, I calculated that the Lachlan River at 1,547 km if it flows all the way to the Murrumbidgee River, and equals the length calculated for the Darling River. The main discrepancy between the measurements is that the Lachlan River snakes it way down at a much finer level than the Darling River, adding 15% to the estimated length.

RiverStatesLength
QGISGeoAustralia
Murray RiverNSW, VIC, SA2,508 km
Murrumbidgee RiverACT, NSW1,616 km1,485 km
Darling RiverNSW1,547 km1,545 km
Lachlan RiverNSW1,547 km1,339 km
Cooper CreekQLD, SA1,113 km
Flinders RiverQLD1,013 km
Diamantina RiverQLD, SA941 km

Note, while distances should be fairly accurate, but other information was scraped from various online sources and I can't confirm the accuracy of this yet. If you see an error, let me know!

The main section of the river is below Cowra. This starts off in the lower inland slopes of the Great Dividing Range but is mostly on the flat expansive alluvial plains of the South West Slopes and Riverina regions that provide fertile agricultural land for many farms.

Key Waypoints

  • 0 km(-253 km)

    Source

    Elevation 682 m
    Coordinates 34° 46' 6.6" S, 149° 26' 25.1" E

    ...

  • 253 km(0 km)

    Cowra

    Distance between locations 253 km Elevation 285 m Slope 1.57‰
    Coordinates 33° 50' 3.5" S, 148° 41' 3.1" E
    Population 9,800 Supermarket(s) Climate
    Gauge: Cowra, BOM; WaterNSW
    Flood: minor: 8.5 m, moderate: 10.7 m, major: 13.4 m
    Flow: no flow: 0.91 m, recommended: 1.2 m to 1.6 m plus

    ....

  • 313 km(60 km)

    Gooloogong

    Distance between locations 59.7 km Elevation 264 m Slope 0.35‰
    Coordinates 33° 36' 22.7" S, 148° 25' 55.2" E
    Population 300 General Store
    Gauge: Nanami, WaterNSW
    Flow: no flow: 0.1 m, recommended: 0.45 m to 1.07 m plus

    ....

  • 416 km(162 km)

    Forbes

    Distance between locations 102.5 km Elevation 237 m Slope 0.26‰
    Coordinates 33° 24' 8.3" S, 148° 1' 11.3" E Date Lachlan Valley Way
    Population 8,400 Supermarket(s) Climate
    Gauge: Cottons Weir, BOM; WaterNSW
    Flood: minor: 3.5 m, moderate: 5.3 m, major: 6.6 m
    Flow: no flow: 0 m, recommended: 0.36 m to 0.63 m plus

    ....

  • 631 km(378 km)

    Condobolin

    Distance between locations 215.4 km Elevation 186 m Slope 0.24‰
    Coordinates 33° 5' 29.4" S, 147° 8' 49.6" E Date The Gipps Way
    Population 3,500 Supermarket(s) Climate
    Gauge: West Condobolin Weir, BOM; WaterNSW
    Flood: minor: 5.2 m, moderate: 5.9 m, major: 6.7 m
    Flow: no flow: 1.35 m, recommended: 1.5 m to 1.8 m plus

    ....

  • 763 km(509 km)

    Euabalong

    Distance between locations 131.7 km Elevation 158 m Slope 0.21‰
    Coordinates 33° 6' 43.2" S, 146° 28' 34.3" E Date Lachlan Valley Way
    Population 200

    No stores?

  • 1,038 km(785 km)

    Hillston

    Distance between locations 275.5 km Elevation 121 m Slope 0.13‰
    Coordinates 33° 29' 0.2" S, 145° 32' 1.7" E Date Swing Bridge
    Population 1,450 Supermarket(s) Climate
    Gauge: Hillston Weir, BOM; WaterNSW
    Flood: minor: 2.4 m, moderate: 2.8 m, major: 3 m
    Flow: no flow: 0.09 m, recommended: 0.49 m to 0.9 m plus

    ....

  • 1,240 km(987 km)

    Booligal

    Distance between locations 201.9 km Elevation 93 m Slope 0.14‰
    Coordinates 33° 51' 44.6" S, 144° 53' 7.1" E Date Cobb Hwy
    Population 100
    Gauge: Booligal Weir, BOM; WaterNSW
    Flood: minor: 2.4 m
    Flow: no flow: 0.16 m, recommended: 0.51 m to 0.75 m plus

    Hotel and maybe a general store.

  • 1,494 km(1,241 km)

    Oxley

    Distance between locations 253.8 km Elevation 73 m Slope 0.08‰
    Coordinates 34° 11' 51.0" S, 144° 6' 38.2" E Date Oxley Rd Crossing
    Population 160
    Gauge: 4 Mile, WaterNSW
    Flow: no flow: 0.08 m, recommended: 0.83 m to 2.02 m plus

    This marks the end of flow under dry conditions. Good flows will make it into the Great Cumbung Swamp, but only large floods make it to the Murrumbidgee River.

    Appears to be no stores here. The 4 Mile gauge is about 15 km upstream.

  • 1,547 km(1,294 km)

    Murrumbidgee

    Distance between locations 53.3 km Elevation 67 m Slope 0.11‰
    Coordinates 34° 21' 18.0" S, 143° 57' 1.8" E

    As noted, this only flows during larger flood conditions. It is 131 km from Balranald, 235 km from the Murray.

Key towns along the river are shown below.

  • Source
  • Cowra
  • Gooloogong
  • Forbes
  • Condobolin
  • Euabalong
  • Hillston
  • Booligal
  • Oxley
  • Murrumbidgee River

Distance table

The distances were calculated by manually digitizing the river path from Bing aerial images in QGIS (WGS 84 / UTM Zone 55S).

Distance (KM) Source Cowra Gooloogong Forbes Condobolin Euabalong Hillston Booligal Oxley Murrumbidgee
Source 0 253 313 416 631 763 1038 1240 1494 1547 Source
Cowra 253 0 60 162 378 509 785 987 1241 1294 Cowra
Gooloogong 313 60 0 103 318 450 725 927 1181 1234 Gooloogong
Forbes 416 162 103 0 215 347 623 825 1078 1132 Forbes
Condobolin 631 378 318 215 0 132 407 609 863 916 Condobolin
Euabalong 763 509 450 347 132 0 276 477 731 785 Euabalong
Hillston 1038 785 725 623 407 276 0 202 456 509 Hillston
Booligal 1240 987 927 825 609 477 202 0 254 307 Booligal
Oxley 1494 1241 1181 1078 863 731 456 254 0 53 Oxley
Murrumbidgee 1547 1294 1234 1132 916 785 509 307 53 0 Murrumbidgee

Refer to the planning page for a complete distance table including most weirs and important rivers.