State of the Environment

2006

Indicator: IW-13 Catchment sediment load

Data

Suspended sediment loads for 500 km2 sub catchments

Suspended sediment loads for 500 km<sup>2</sup> sub catchments

Source: National Land and Water Resources Audit 2002, Australian Catchment, River and Estuary Assessment 2002, volumes 1 and 2, Land and Water Australia, viewed 16 Dec 2005, http://audit.ea.gov.au/anra//coasts/docs/estuary_assessment/River_Findings.cfm.

Condition of river reaches based on the nutrient and suspended sediment load subindex

Condition of river reaches based on the nutrient and suspended sediment load subindex

Source: National Land and Water Resources Audit 2002, Australian Catchment, River and Estuary Assessment 2002, volumes 1 and 2, Land and Water Australia, viewed 16 Dec 2005, http://audit.ea.gov.au/anra//coasts/docs/estuary_assessment/River_Findings.cfm.

Particulate (sediment-bound) phosphorus (tonnes/year) by major region
Region Hillslope Gully Bank Floodplain sedimentation Reservoir sedimentation
Far North Qld 2 942 106 144 1 184 0
North Qld 3 966 129 187 1 292 140
Burdekin 1 909 1 271 309 8 185 2 960
Fitzroy 9 526 1 008 519 8 377 919
Moreton Bay 971 93 209 538 254
Qld South 2 426 336 277 1 748 362
Murray-Darling Basin 10 719 4 387 4 434 16 295 3 977
NSW North 987 277 396 572 10
NSW South 1 902 667 428 1 314 279
Vic East 207 183 216 303 13
Vic West 41 213 174 285 17
SA Gulf 146 204 78 309 19
WA South 53 1 009 299 1 254 17
Indian 46 342 111 466 0
Tasmania 244 87 358 73 25
Totals/averages 46 086 10 312 8 138 42 194 8 992

Adapted from Source: National Land and Water Resources Audit 2001, Rivers - nutrient loads and transport, Land and Water Australia, Canberra, viewed 16 Apr 2005, http://audit.ea.gov.au/ANRA/water/water_frame.cfm?region_type=AUS&region_code=AUS&info=river_nutrient.

Particulate (sediment-bound) nitrogen (tonnes/year) by major region
Region Hillslope Gully Bank Floodplain sedimentation Reservoir sedimentation
Far North Qld 15,457 425 575 5,826 0
North Qld 15,789 515 746 5,123 559
Burdekin 33,615 5,084 1,234 23,528 7,695
Fitzroy 29,108 4,033 2,077 27,086 3,112
Moreton Bay 5,205 373 837 2,035 1,747
Qld South 9,179 1,346 1,108 6,501 1,290
Murray-Darling Basin 36,352 17,556 17,736 53,309 15,952
NSW North 7,759 1,108 1,583 3,682 38
NSW South 8,926 2,666 1,710 5,364 1,590
Vic East 1,500 731 865 1,222 39
Vic West 527 851 694 1,167 78
SA Gulf 905 815 313 1,294 65
WA South 982 4,038 1,196 4,481 57
Indian 445 1,368 444 1,972 0
Tasmania 1,536 348 1,432 369 255
Totals/averages 170,264 43,999 34,130 148,605 32,559

Source: National Land and Water Resources Audit 2001, Rivers - nutrient loads and transport, Land and Water Australia, Canberra, viewed 16 Apr 2005, http://audit.ea.gov.au/ANRA/water/water_frame.cfm?region_type=AUS&region_code=AUS&info=river_nutrient.

Nutrient and suspended sediment load subindex for each State and the Australian Capital Territory
Total length of reach (km) in each category and percentage of total in parentheses Percentage of total length with data
Largely unmodified Moderately modified Substantially modified Extensively modified
Queensland 2809 (4) 12660 (20) 40347 (64) 7573 (12) 88
New South Wales 1692 (3) 23784 (41) 27630 (48) 4678 (8) 97
Australian Capital Territory 9 (3) 89 (33) 172 (64) 0 (0) 100
Victoria 4419 (29) 5067 (33) 5287 (35) 410 (3) 96
Tasmania 3233 (59) 1811 (33) 429 (8) 0 (0) 98
South Australia 210 (3) 2860 (39) 4112 (55) 203 (3) 76
Western Australia 870 (4) 2988 (15) 15759 (78) 461 (2) 98
Total 13242 (8) 49258 (29) 93736 (55) 13324 (8) 81

Source: National Land and Water Resources Audit 2001, Rivers - nutrient loads and transport, Land and Water Australia, Canberra, viewed 16 Apr 2005, http://audit.ea.gov.au/ANRA/water/water_frame.cfm?region_type=AUS&region_code=AUS&info=river_nutrient.

Murray Darling Basin

Total sediment supply to rivers in the basin is estimated at 29 million tonnes per year, which is 41 times the natural rate. River channels in over 60% of the Basin carry sediment loads that are more than 20 times the natural loads.

Less than 1% of this sediment is exported to the coast. The rest of the sediment is deposited on floodplains (46%), in river beds (33%) or in reservoirs (21%).

Source: Gehrke, P Gawne, B and Cullen, P 2003, What is the status of river health in the Murray-Darling Basin?, CSIRO Land and Water, Canberra, viewed 14 Oct 2005, http://www.clw.csiro.au/priorities/.

What the data mean

Nutrient and suspended sediment loads are greater than natural levels for over 90% of river length, and are severely modified in almost 10% the total river length.

Areas with the highest increase in phosphorus and suspended sediment loads include the north-east part of the Murray-Darling Basin, and areas subject to intense summer storms where gully erosion occurs on erodible and bare soils.

Some Queensland catchments (e.g. the Herbert River Basin) are severely modified in terms of sediment loads and this reflects the intense summer rainfall and seasonally low vegetation cover associated with large areas of cattle grazing.

In Western Australia, the natural sediment yield is very low, so even a relatively small increase in suspended sediment load can be significant.

The major sink for phosphorus and nitrogen is floodplain sedimentation.

Data Limitations

NLWRA 2001 data has not been updated.

Issues for which this is an indicator and why

Inland Waters - Catchment scale influences - Land and vegetation condition - Nutrients and sediments - sources and loads 

Sediment loads is a direct measure of the pressure of nutrients and sediments on land and vegetation condition.

Other indicators for this issue:

Inland Waters - Catchment scale influences - Land and vegetation condition - Erosion 

Catchment erosion can lead to sedimentation, which can significantly alter the physical habitat of instream environments. Sediment loads in inland water catchments is one measure of the quantity of soil being eroded into waterways.

Other indicators for this issue:

Inland Waters - Habitat scale influences - In-stream habitat - woody debris and sand slugs 

Catchment sediments can accumulate in streams and smother bed habitats and fill deep pools, which can significantly alter the physical habitat of instream environments. Sediments also supply nutrients and change the food web structure of an ecosystem. Sediment loads in inland water catchments is one measure of the quantity of soil being eroded into waterways.

Other indicators for this issue:

Inland Waters - Habitat scale influences - Water Quality (for surface and groundwater) - Sediment and turbidity 

Sediment can disrupt habitats by bringing with it nitrogen and phosphorous and through increased turbidity. Sediment loads in inland water catchments is one measure of the likelihood of turbidity occurring.

Other indicators for this issue:

Land - Contributions and pressures between the land and inland water - Pressures of changes to the land on inland waters 

Agricultural land use disturbs soils and can change loads of sediment entering inland waters, placing pressure aquatic species as well as on terrestrial species that rely on the water source. Quantities of sediment concentrating in surface water catchments are a direct measure of this pressure.

Other indicators for this issue:

Land - Contributions and pressures between the land and the ocean - Pressures of land changes on the coasts and oceans 

Agricultural land use disturbs soils and can change loads of sediment entering inland waters and ending up in coastal waters where in can place pressure aquatic and estuarine species as well as on other coastal species that rely on the water source. Quantities of sediment concentrating in surface water catchments are a direct measure of this pressure.

Other indicators for this issue:

Coasts and Oceans - Contributions and pressures between the coasts and oceans and inland water - Effect of changes in inland waters on the coasts and oceans 

Sediment loads carried by inland waters can end up in coastal waters where sediments can place pressure aquatic and estuarine species as well as on other coastal species that rely on the water source. Quantities of sediment in surface water catchments are a direct measure of this pressure.

Other indicators for this issue:

Coasts and Oceans - Contributions and pressures between the coasts and oceans and land - Effects of changes in the land on the oceans 

Sediments and nutrients from the land can place pressure on coastal and estuarine waters.

Other indicators for this issue:

Further Information

NLWRA 2002

Key

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