Resource Condition Summary
The Lower Burdekin Basin is relatively small (~ 9,292 sq. km.)
and covers around 7% of the Burdeki WQIP region. Common to most of
the BQWIP basins, land use is dominated by grazing on native
pastures. However, in contrast to the other Basins, approximately
12% of the land area is used for intensive agriculture (mostly
irrigated sugar production), while around 9% is set aside for
conservation and minimal use1. The condition of riparian
habitat varies between subcatchments, from fair (B) to very poor
(D). There has been a general decline in condition over the last 30
years, principally due to clearing along streams and
floodplains2. The lower areas of the four coastal
subcatchments represent a single floodplain which is considered to
contain the single most important, healthy and productive wetland
systems in the Burdekin region and, indeed, along the Queensland
coast. It includes many large, permanent freshwater wetlands, long
lengths of perennially-flowing creeks, and estuarine wetlands that
are recognized internationally as Ramsar wetlands and listed in the
National Directory of Important Wetlands (DOIW). However, the flow
regime of much of the lower Burdekin floodplain has been altered
from seasonal to perennial flow by the tailwater discharge from the
development of extensive system of irrigation channels for
agriculture. In contrast, the two non-coastal subcatchments
(Burdekin (below dam), Landers Creek & Stones Creek) and upper
parts of the Haughton River, Barratta Creek and Upstart Bay
subcatchments are mostly dry, ephemeral creek
systems3.
Stream bank erosion is identified as the major source of
sediment and particulate nutrients affecting water quality in the
Lower Burdekin Basin, mostly sourced from the Burdekin River.
Hillslope erosion dominates in the non-Burdekin River
subcatchments4. The rate of soil erosion for the Basin overall is
predicted to be high and well above the BWQIP region average, with
some individual subcatchments predicted to lose from two to four
times the BWQIP region average. The Burdekin River (below dam)
subcatchment, in particular, is predicted to have a very high rate
of soil erosion and to contribute substantially to the total
sediment load at end-of-catchment. While coverage of field survey
data of grazing land condition is quite limited within the basin,
analyses of ground cover from satellite imagery7,8
identify the Burdekin River (below dam) subcatchment to be in
poorest condition and to have large areas that are particularly
vulnerable to further soil erosion.
Water quality in the Burdekin River is predicted by models to
have only slightly elevated concentrations of suspended sediment
and particulate nutrients at the end-of-basin during wet season
flow events, notwithstanding the very large sediment and nutrient
load that is derived from the entire Burdekin River catchment
upstream4. Water quality monitoring data over 8 wet
seasons recorded sediment loads in the Burdekin River well in
excess of the modelled predictions and show that the total sediment
load is underestimated in the model by as much as
43%9,10. In contrast, water quality monitoring data from
the other coastal rivers and creeks of the Lower Burdekin Basin
that drain the irrigated agricultural areas of the floodplain show
that suspended sediment concentrations and loads are much lower
than predicted by models ! However, disproportionately high
dissolved inorganic nitrogen concentrations and loads, which is
attributed largely to fertilizer use in irrigated agriculture, have
been recorded from the Haughton River, and Barratta, Sheep Station,
Plantation and Iyah Creeks. Nevertheless, the measured total load
of dissolved inorganic nitrogen (DIN) from the Burdekin River
catchment rangelands greatly exceeds that delivered to the GBR
through coastal streams draining the irrigated agricultural areas
of the Lower Burdekin10. Several herbicide residues have
also regularly been detected in coastal rivers and creeks,
including atrazine, diuron, ametryn and hexazinone. Elevated
concentrations of tebuthiuron have been recorded from catchments
draining grazing land, particularly the Burdekin and Haughton
Rivers11.
Draft Water Quality Targets
The following water quality Resource Condition Targets were
developed based on Best Management Practice Guidelines for Water
Quality Improvement, extensive modelling of a range of management
scenarios, preparation of a discussion paper12 and then,
finally, a series of workshops. These preparatory activities were
undertaken in collaboration with landholders (graziers and cane
farmers), industry representatives, Government, the scientific
community and NQ Dry Tropics staff.
- By 2058, attain a minimum 40% (to maximum 50%) reduction in
mean annual sediment load at end of Burdekin Catchment (Inkerman
Bridge/Claire Weir) from current (2008) - i.e. a reduction from
approximately 3,700 kt/yr to 2,220 kt/yr)
- By 2058, attain a 60% (minimum) to 80% reduction in nitrogen
(nitrate) load entering the GBR from Lower Burdekin sugar and other
irrigated lands from current (2008) - i.e. a reduction from
approximately 3,000t/yr to 600 t/yr)
- By 2013, attain an 8% (minimum) to 25% reduction of nitrogen
(nitrate) load entering the GBR from Lower Burdekin sugar lands
from current (2008) - i.e. a reduction from approximately 3,000
t/yr to 2,250 t/yr)
- By 2013, attain a 25% (minimum) to 50% reduction of pesticide
(atrazine, diuron, ametryn, hexazinone) load entering the GBR from
Lower Burdekin sugar lands from current (2008)
The following Management Action Targets correspond to the Lower
Burdekin irrigated agricultural areas:
- 3% (minimum) to 16% of sugar land is managed under BSES
‘6 easy steps’ or other innovative management regime
(e.g. N replacement) by 2013
- High nitrogen application rates of approximately 330 kg N/ha
(plant) / 400 kg/ha (ratoon) are reduced to 190-210 kg N/ha (plant)
/ 270 kg N/ha (ratoon) or lower on between 2% and 11% (maximum) of
sugar land by 2013
Footnotes: see References
