Lachlan River & Wetlands

The Lachlan River

The named Lachlan River starts in the east as a chain-of-ponds in a drained lake basin near the village of Breadalbane, between Yass and Goulburn. The Lachlan is the fourth longest of both Australia’s rivers and of the twenty-three major rivers in the Murray–Darling Basin (approximately 1339 river kilometres in length; Geoscience Australia, 2012). While a tributary of the Murrumbidgee River (Outhet, 2011), the Lachlan River effectively terminates in the west as a large, expansive system of wetlands and effluent (diverging) creeks known as the Great Cumbung Swamp (Green et al. 2011; NSW Fisheries Scientific Committee, 2005).

Meandering Lachlan River in the Great Cumbung Swamp (Simon Hunter, OEH, 21 December 2010).

Meandering Lachlan River in the Great Cumbung Swamp (Simon Hunter, OEH, 21 December 2010).

It only connects to the Murrumbidgee River downstream during periods of exceptionally high flow (in about 10–20% of years; O’Brien & Burne, 1994). For this reason, the Lachlan Catchment is considered a unique region in the Murray–Darling Basin (MDB) (Barma Water Resources et al., 2011) and is one of just two disconnected MDB tributaries. Disconnected tributaries do not contribute significant flows to the two major MDB component systems, the Darling and Murray rivers. Therefore, under the Basin Plan the Murray-Darling Basin Authority (MDBA) did not propose to recover any additional water for the environment for ‘shared’ targets. Shared targets are in addition to individual catchment targets and are for meeting downstream needs such as the lower lakes, Coorong and for flushing salt from the Murray mouth. The Hon. Katrina Hodgkinson, in her role as Minister for Primary Industries and with administrative responsibility for the NSW Water Management Act 2000, represents NSW on the Murray Darling Basin Ministerial Council.

 Overview of Lachlan Catchment Wetlands

In a state-wide mapping project involving 17 catchments, the total area of wetlands in the Lachlan was estimated at 471,011 ha or 5.6% of the total catchment area  (compared to the state average of 6.5% or a total wetland area of 66,580,826 ha; Kingsford et al., 2003). The Lachlan Catchment ranked seventh in terms of the proportion of total catchment area which was comprised of wetlands, with a value similar to the Darling and Lower Murray (NSW portion only) catchments. The 12 catchments (including the Lachlan) with 6% or less of wetland area in their catchment included most of the major regulated rivers in NSW. A table summarising the state-wide mapping project (Kingsford et al., 2003) with reference to the relative ranking of the Lachlan Catchment can be viewed by expanding the NSW Wetlands Summary Table menu below.

NSW Wetlands Summary Table

Catchment Name Total Catchment Area (ha)a Total Wetland Area (ha)b % of Total Wetland Area relative to Total Catchment Area (b/a*100) Total Reservoir Area (ha)   No. of Reservoirs
Condalmine-Culgoa (NSW) 2 611 171 738 867 28.30 (1) 102 24 (11)
Warrego (NSW) 1 138 944 311 952 27.39 (2) 1000 9 (12)
Murray-Riverina 1 502 859 262 430 17.46 (3) 3468 85 (9)
Paroo (NSW) 4 115 249 666 913 16.21 (4) 177 7 (13)
Lake George 94 069 13 018 13.84 (5) 57 3 (14)
Macquarie-Bogan 7 463 395 421 516 5.65 (6) 13 391 239 (2)
Lachlan 8 470 000 471 011 5.56 (7) 7769 163 (4)
Darling 11 258 100 581 135 5.16 (8) 2983 121 (7)
Lower Murray (NSW) 928 457 46 161 4.97 (9) 744 160 (6)
Far north-west 6 543 731 274 322 4.19 (10) 511 160 (6)
Murrumbidgee 8 152 712 277 369 3.40 (11) 18 526 337 (1)
Benanee 2 129 292 63 834 3.00 (12) 0 0 (15)
Border and Moonie (NSW) 2 463 285 60 949 2.47 (13) 3309 88 (8)
Gwydir 2 659 603 58 907 2.21 (14) 15 650 193 (3)
Namoi 4 195 075 52 677 1.26 (15) 8721 162 (5)
Castlereagh 1 739 480 16 949 0.97 (16) 1041 121 (7)
Upper Murray (NSW) 520 544 292 0.02 (17) 6967 26 (10)

Total areas (ha) of catchments, wetlands and reservoirs, and total number (no.) of reservoirs for the 17 NSW catchments adapted from Table 3 in Kingsford et al., (2003). Relative ranks are from greatest to least and are shown in parentheses ().

In the Lachlan Catchment, of the three spatially derived wetland groups (and reservoirs) for inland wetlands, 95% are floodplain wetlands and 5% freshwater lakes, with no saline lakes mapped (Kingsford et al., 2003). The dominance of the floodplain wetland group was common across NSW, with over 70% of wetland area classified as floodplain for all but two of the 17 catchments, with an average of 93% floodplain across the state.

Reservoirs, which reflect the level of river regulation and development to some extent, were also mapped and included open bodies of water usually created by a wall or levee, such as reservoirs, farm dams, off-river storages, mining and quarry dams, sewage ponds, evaporation ponds, evaporation basins, canals and open basins (Kingsford et al. 2003). The Lachlan Catchment was ranked as containing the fourth greatest total number of reserviors at 163 structures.

Lachlan Environmental Water Management Plan and Lachlan Catchment Wetlands

One objective of the LEWMP is to set priorities for environmental watering. To assist in this process a number of wetlands have been recognised at national and regional levels as containing ecological, cultural or social values. These wetlands are included as priorities for the delivery of environmental water.

This website contains specific sections accessed via the internal hyperlinks on the eight Nationally Significant Wetlands and nine Regionally Significant Wetlands, and other important in-channel water-dependent assets and priority locations (Riverine Key Features and Priorities) within the Lachlan Catchment.

 

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