- Much of the runoff from the BRIA is directly discharged to Barratta Creek , compared to the Delta where the waterways are typically used as water transfer channels . Recycle pits are also commonly used in the BRIA to capture and recycle irrigation tailwater .
- The soils in the Delta are also more permeable than in the BRIA , making them less suitable for achieving efficient furrow irrigation techniques .
- In the Delta , the majority of irrigators are groundwater irrigators , where irrigation water recharges the aquifer and is subsequently reused to maintain soil moisture requirements .
- Delta growers apply more water per unit of area ( e . g . 20 + ML / ha ) than BRIA growers ( e . g . 10- 12ML / ha ). Reasons include high soil permeability ( irrigation water leaches quickly ) in the Delta and most of the irrigation water is charged via area ($/ ha – not a volumetric charge ) in the Delta . These factors affect the relative economic benefit accrued from improvements in water application efficiency .
- There are 347 farms in the BRIA and 580 farms in the Delta . The average farm size in the BRIA is 140ha ( with areas up to 3,500ha ) compared to 72ha in the Delta ( with areas up to 500ha ). Economic analysis conducted by Smith ( 2015 ) indicates that it is more cost effective to implement improved nutrient and irrigation management practices on the larger farms as fixed costs are spread across a larger production base .
� The dominant water quality issues from sugarcane area in the Lower Burdekin are DIN and pesticides .
� The timing of losses is a critical factor in determining the relative risk of these pollutants to the receiving environments including groundwater , freshwater , estuarine , coastal and coral reef ecosystems . For DIN losses , the highest risk is to freshwater systems in the dry season from irrigation runoff and first flush events , and to coastal and inner shelf marine ecosystems in periods of high flow . Mid and outer shelf reefs can also be susceptible to DIN runoff from the Lower Burdekin during large wet season events when the discharge combines with river plumes from the larger Burdekin River when the influence can extend hundreds of kilometres north . For pesticides , the highest risk is to freshwater systems in the dry season from irrigation runoff and first flush events . For coastal and marine ecosystems , the potential influence is highly variable depending on timing and location but is typically only linked to periods of high flow and constrained to inner shelf systems .
� The Reef 2050 Water Quality Improvement Plan 2017-2022 includes updated targets for managing water quality in the GBR . The proposed Irrigation Extension and Investment Plan should adopt the management practice adoption and human dimensions targets and have regard to the riparian vegetation and natural wetlands targets . The actions must be designed to accelerate progress towards achieving these targets .
� Basin-specific DIN reduction targets have been established and are described in Section 3.4 ; these are defined for the Haughton and Burdekin basins , but not the Lower Burdekin area specifically . Having two separate targets within the Lower Burdekin sugarcane area is considered by extension providers and growers to be confusing . Based on current knowledge , it is reasonable to suggest that the target for the annual average anthropogenic DIN reduction from sugarcane the Lower Burdekin catchment by 2025 is in the vicinity of 720 tonnes . For pesticides , the target for all GBR catchments is to protect at least 99 per cent of aquatic species at the end of the catchment .
� The 2017 Scientific Consensus Statement identified management priorities for the 35 GBR basins and these have been adopted in the Reef 2050 WQIP . The Haughton Basin ( which covers a large part of the Lower Burdekin sugarcane area ) is considered a Very High priority basin for DIN management , and the Burdekin Basin is a Moderate priority . For pesticides , the Haughton is considered a High priority basin . These priorities were identified as a result of biophysical assessment only , and it is recognised that to determine priorities within catchments , human dimensions factors need to be considered . Management actions in the Lower Burdekin sugarcane area must be designed to achieve significant reductions in DIN and PSII herbicide losses over the next 7 years .
� Many years of work in the Lower Burdekin highlights the need to establish local and regional groundwater targets , in terms of quantity ( water table depths ) and quality . While these need to be spatially specific , it is not yet clear whether a temporal component is required .
x