Executive Summary
Two major integrated projects ( MIPs ) were recommended by the Great Barrier Reef ( GBR ) Water Science Taskforce in its final report released in May 2016 ( www . gbr . qld . gov . au / taskforce / final-report /). The Queensland Government has agreed to implement this recommendation to reduce nutrient , sediment and pesticide loads in the Wet Tropics and Burdekin regions . The MIPs aim to concentrate interventions and management efforts at a catchment scale and fully evaluate their effectiveness in improving water quality . The Burdekin MIP ( BMIP ) is being conducted in the Bowen Broken Bogie catchment with a focus demonstrating the best approaches to reducing sediment and particulate nutrient delivery to the Great Barrier Reef ( GBR ).
The purpose of this report is to complete a comprehensive Synthesis Report for the BBB catchment utilising extensive existing biophysical , land management practice , social and economic data . It will be used in conjunction with a set of design workshops to inform the completion of Stage One Design Phase of the BMIP . The report has been developed in conjunction with the design process , and it is suggested that this information base is updated periodically throughout the implementation of the BMIP .
The following key findings are relevant to start the process of establishing a 2017 baseline of biophysical , land management practice , social and economic data for the catchment and inform prioritisation of investment , best location and actions for project design . Further work is required to complete a comprehensive baseline for the program which is described in the Monitoring and Evaluation Strategy for the Program Design .
Sources
• The Burdekin Water Quality Improvement Plan identifies the BBB catchment as the highest priority catchment for sediment loss in the Burdekin NRM region , followed by the Upper Burdekin catchment , supported by multiple lines of evidence including monitoring , tracing studies and modelling .
• This catchment has some of the highest sediment concentrations and one of the highest per-hectare sediment loads of any catchment draining to the GBR lagoon , and these erosion rates are estimated to be ~ 7.5 times higher than natural .
• Grazing land use is the dominant contributing land use of TSS in the BBB . Across the whole BBB , it is predicted that gully erosion is the dominant erosion source ( 65 %), followed by hillslope ( 27 %) and streambank ( 8 %) erosion . These proportions vary between sub catchments , but gully erosion is the dominant sediment source , except in the Broken River sub catchment where hillslope erosion dominates ( 65 %).
• There is some evidence of severe bank erosion ( i . e . steep , bare banks with pipe erosion ) at a number of mine sites in the upper section of the Little Bowen subcatchment , and there is considerable severe gully erosion in the Little Bowen .
• There are several large mining operations in the BBB including 4 coal mining operations and one operating gold mine . There are also estimated to be 119 abandoned mines . Where mining impacts or risks are high , there is usually information in mine approval or operational management plans associated with their licensing . Gully and stream bank erosion is also important in these areas , in addition to disrupted waterway and aquifer hydrology , mining associated infrastructure development and storm event driven mobilisation of minerals or chemicals . However , comprehensive research into the cumulative effects and unlicensed risks of mines to waters in the region is yet to be undertaken .
• Within BBB catchment , sediment is delivered from a relatively small proportion of the area which has vulnerable soils that are well‐connected to the stream network . These are primarily where subsoil is exposed in scalds , rills and gullies . These features can be identified in the landscape , but the critical gap in our understanding is the effectiveness of erosion remediation options for controlling these sources of sediment at property and sub-catchment scales .
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