Resource Condition Summary
The Bowen Broken Bogie Basin is relatively small (~ 11,730 sq.
km.) and covers around 9% of the BWQIP region. Common to most of
the BQWIP basins, land use is dominated by grazing on natural
pastures. However, approximately 24% of the land area is set aside
for conservation and minimal use, most of which lies within the
Broken River subcatchment. While the condition of riparian habitat
varies markedly between subcatchments, from good (A) to very poor
(D), there has been a general decline in condition over the last 30
years, principally due to clearing along streams and floodplains.
Similarly, there is great diversity in the value of aquatic
habitats, and knowledge of their condition and ecology between
subcatchments. Waterways vary between largely sandy, dry ephemeral
creek systems to permanently flowing clear-water rivers and creeks
that originate in mountain rainforest.
Hillslope erosion is identified by models as the major source of
sediment and particulate nutrients affecting water quality within
the Bowen Broken Bogie Basin, while gully and streambank erosion
are also identified as a significant contributors. The rate of soil
erosion for the Basin overall is predicted to be high and well
above the BWQIP region average, with individual subcatchments
losing up to almost three times the BWQIP region average. The
Bowen, Little Bowen, Broken, Pelican Creek and Bogie River
subcatchments are all predicted to have high rates of soil erosion
and to contribute substantially to the total sediment load at
end-of-catchment. Rapid assessment of grazing land condition rates
most of land area to be in poor (C) or fair (B) condition. However,
analyses of ground cover from satellite imagery (reference)
identify extensive areas of chronic, vulnerable and marginal 'D'
condition land, while gully erosion is reported to be extensive in
some areas.
Water quality in the Bowen Broken Bogie Basin is predicted by
models to have moderately to highly elevated loads and
concentrations of suspended sediment at the end-of-basin during wet
season flow events. However, water quality monitoring from the
Bowen River over 5 years have recorded still much higher sediment
concentrations and loads than predicted by models
! In contrast, sediment concentrations
and loads from the Broken River subcatchment have been calculated
to be lower than predicted by models
!
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 paper (reference) 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% reduction in mean annual sediment
load from the Bowen-Broken River sub-basin (measured at Myuna) from
current (2008) - i.e. a reduction from approximately 1,355 kt/yr in
2008 to 813 kt/yr by 2058).
