Resource Condition
Summary
The Upper
Burdekin Basin is the largest in the Burdekin Dry Tropics NRM
region (~ 40,412 sq. km.) and covers around 30% of the Burdekin
WQIP region. Common to most of the Burdekin WQIP basins, land
use is dominated by grazing on native pastures. Approximately 11%
of the land area is set aside for conservation and minimal use,
mostly as remnant native vegetation, while a great many abandoned
and operational mines within the basin1. The condition of riparian
habitat varies greatly between subcatchments, from good (A) to very
poor (D)2.
Similarly, there is great diversity in aquatic habitats, and
knowledge of their condition and ecology. Waterways vary between
largely sandy, dry ephemeral creek systems to permanently flowing
clear-water rivers and creeks that originate in mountain
rainforest3.
Hillslope
erosion is identified by models as the major source of sediment and
particulate nutrients affecting water quality within the Upper
Burdekin Basin, while stream bank and gully erosion are also
identified as a significant contributors overall4. The
rate of soil erosion for the Basin overall is predicted to be
moderate and close to the BWQIP region average, with some
individual subcatchments predicted to lose up to twice the BWQIP
region average. The Burdekin River (above dam) and Burdekin River
(Blue Range) subcatchments, in particular, are predicted to have
high rates of soil erosion and to contribute substantially to the
total sediment load at end-of-basin. The Clarke River subcatchment
is also predicted to contribute substantially to the end-of-basin
sediment load. Field surveys of grazing land identifies quite
similar proportions of land to be in good (A), fair (B) and poor
(C) condition overall5,6. Analyses of ground cover from
satellite imagery7,8 identify some quite extensive areas
of chronic 'D' condition land, and highly vulnerable and marginal
'D' condition land, while stream bank and gully erosion are
reported to be extensive in some areas.
Water quality
in the Upper Burdekin Basin is predicted by models to have
moderately elevated loads and concentrations of suspended sediment
at the end-of-basin during wet season flow events4.
However, water quality monitoring from the Burdekin River at
Sellheim over 5 years have recorded still much higher sediment
concentrations and loads than predicted by models9,10.
While the Burdekin Basin is evidently the major contributor of
sediment and particulate nutrient loads to the BFD, it is estimated
that as much as 60% may be trapped within the dam during an average
event flow10, thus reducing quite significantly its
total suspended sediment contribution to the Burdekin River
mouth.
Draft Water
Quality Targets
The following
water quality Resource Condition Target was 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.
- Attain a minimum 40% reduction in mean annual
sediment load from the Upper Burdekin Basin (measured at Sellheim)
from current (2008) by 2058 (i.e. reduction from approximately
2,150 kt/yr in 2008 to 1,290 kt/yr by 2058)
Footnotes: see References
