Prepared by Cameron Dougall and David Waters , Queensland Department of Resources ( with support from Zoe Bainbridge , TropWATER , James Cook University )
The Queensland Government , through the Paddock to Reef program , committed resources to undertake catchment modelling for the Burdekin Landholders Driving Change ( LDC ) Project . The main aim of the modelling is to provide feedback on the expected sediment and particulate nutrient savings , resulting from the projects on-ground works . The priority sub-catchments being the Bowen-Bogie-Broken ( BBB ) of the Burdekin ( Figure 1 ). Scenario modelling directly allows the overall contribution of the “ LDC Project ”, to the “ Burdekin catchment Reef targets ” to be determined for the relevant timeframe . Key components of the LDC Project include undertaking a wide range of on-ground activities such as gully remediation , better pasture management to retain ground cover and infrastructure improvements to support remediation . Other grazing management activities include controlling vegetation / weed species which reduce grass cover and managing the immediate contributing catchment areas of gully systems .
A secondary aim of the work was added , with the objective of improving the catchment modelling , given the importance of BBB area to overall Reef targets . This component included better integration of new and old monitoring data ( including soils , disparate water quality monitoring , and rainfall ), and the exploration and construction of new layers to better represent changes at smaller scales ( LIDAR , erosion feature mapping ). Importantly , modelling can offer insights that help with understanding and identifying areas for improvement , including through optimal experimental design , and such areas were identified for better water quality monitoring ( e . g ., LDC Community Water Quality Monitoring project led by TropWATER James Cook University ).
Although catchment model scenario results , such as sediment savings from project works are important final outputs of the work , the secondary knowledge and products generated from the modelling process are often overlooked . Indeed , depending on the maturity of catchment knowledge and levels of uncertainty , these may be viewed as a more valuable products than the scenario results themselves . For example , the National Land and Water Gully mapping project highlighted the potential importance of this erosion source in the Great Barrier Reef ( GBR ) catchments , and the resultant interest and interrogation of the layer led to wider-scale scientific investigation into the presence and processes of gullies , and in turn supporting better targeting and modelling .
The project brief of improved catchment modelling for the Paddock to Reef program logically captures the modelling process , which is outlined in detail in Jakeman et . al . ( 2018 ). Steps in model production among others include :
• Scoping
• Model Conceptualisation
• Data collection , cleansing and pre-modelling analysis
• Sensitivity Analysis
• Calibration
• Validation
• Scenario Analysis
• Communication
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