Modelling pesticide runoff from paddocks in the Great Barrier Reef using HowLeaky

Shaw, Mel; Thornton, Craig; Robinson, Ben; McClymont, D.

doi:10.36334/modsim.2011.e5.shaw

Cited by 3 publications

References 7 publications

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Pesticide Sustainable Management Practice (Smp) Including Porous Biochar/Geopolymer Structures for Contaminated Water Remediation

Craig¹,

Bundschuh²,

Thorpe³

2015

geomate

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As a result of agribusiness in Australia and across the world, water is contaminated with nutrients and pesticides which threaten riverine environments, wetlands, urban drinking water supplies and also marine assets such as the Great Barrier Reef (GBR). Much can be done and sustainable management practices (SMP) can be put into place to reduce water impacts from agriculture. Required investment levels are insignificant compared to the economic advantages to be gained from adopting appropriate SMP across Australian and global agribusiness. SMP technologies need to be targeted at specific pesticides (eg. atrazine, simazine, diruron, ametryn, hexazinone, tebuthiuron, dieldrin, metalochlor, 2,4 D, triclopyr, picloram and bromacil). Surface runoff from agricultural enterprises is conventionally managed by retention lagoons facilitating water reuse on-farm, but these can be breached during heavy storms. Long term deep drainage from fields and seepage from lagoons can also lead to contaminated groundwater. Research, development and testing of appropriate non-leaking/reactive spillways and subsurface geostructures needs to take place across the various agricultural industries. For surface water it is suggested that spillways could be designed with replaceable biochar baffles, and for groundwater, trenches of biochar could form Permeable Reactive Barriers (PRB). The potential for green or brown waste material derived biochar products, which could be readily manufactured from farm refuse and manure, needs to be thoroughly investigated in this regard. The challenge for engineers is to come up with geostructural designs which are efficient, cost effective and which will be taken up and embraced by Australian and world agribusiness.

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Pesticide Sustainable Management Practice (Smp) Including Porous Biochar/Geopolymer Structures for Contaminated Water Remediation

Craig¹,

Bundschuh²,

Thorpe³

2015

geomate

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Paddock scale modelling to assess effectiveness of agricultural management practice in improving water quality in the Great Barrier Reef Catchments

Shaw¹,

Ellis²,

Searle³

et al. 2013

Piantadosi, J., Anderssen, R.S. And Boland J. (Eds) MODSIM2013, 20th International Congress on Modelling and Simulation

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Agriculture in the catchment areas adjacent to the World Heritage listed Great Barrier Reef (GBR) Marine Park generates pollutants that are a concern for the health of the Reef. Under the Paddock to Reef Integrated Monitoring, Modelling and Reporting program (P2R) of the Reef Plan, the impacts of improved agricultural management practices on water quality entering the GBR are modelled to evaluate the effectiveness of Government water quality improvement policies. The Source Catchments modelling framework estimates loads of pollutants entering the GBR lagoon from rivers. However, Source Catchments does not have the capacity to represent the collection of management practices available to farmers that affect water quality in runoff and drainage at a paddock scale. Therefore, paddock scale agricultural systems models were used to demonstrate the effects of management practice adoption and to provide input to the catchment scale models. Paddock scale models were used because they represent a level of process detail compatible with the management practice investments and implementation on-ground. A fit-for-purpose modelling approach was used, where the paddock model most suited to a given land use and/or water quality pollutant was applied. Three one-dimensional agricultural systems models were employed; HowLeaky in grains, APSIM in sugarcane with HowLeaky post-processing for herbicides and phosphorous and GRASP in grazing lands. These models share similar soil water balance, ground cover and runoff sub-models. However, they vary in the level of detail, particularly in terms of representing crop growth and in the processes considered, such as pesticide degradation and export. In grains and sugarcane cropping, the pollutant time-series (e.g. load per day per unit area) in the Source Catchments models was replaced with an output time-series from HowLeaky or APSIM for each soil-climate spatial combination. Management practices were grouped into systems classed as A, B, C or D. The proportion of each of these management systems contributing to the modelled loads was adjusted to reflect data on the prevalence of adoption of improved management practices in the GBR catchment. In grazing lands, GRASP pasture utilisation and ground cover time-series outputs were interrogated to derive relationships between changes in grazing system management and changes in the USLE C-factors. The USLE is used to predict hillslope erosion in the Source Catchments model. Scaling indices derived from GRASP outputs were used to adjust the USLE C-factors applied in Source Catchments where management practices had changed. The P2R program has demonstrated the effectiveness of linking paddock scale models or emergent models derived from them with catchment scale models. This has enabled detailed management options to be simulated to investigate broad scale water quality impacts of the adoption of improved agricultural practices.

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Testing two simple pesticide runoff models in Northern Australian agriculture

2013

Piantadosi, J., Anderssen, R.S. And Boland J. (Eds) MODSIM2013, 20th International Congress on Modelling and Simulation

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The Paddock to Reef Integrated Monitoring, Modelling and Reporting program (P2R) (Department of Premier and Cabinet, 2009) is investigating ways to improve agricultural management practices and the quality of water entering the Great Barrier Reef. One of the major risks to GBR water quality is pesticide runoff from agricultural industries. Direct measurement of pesticide fate and behavior is both cost and time intensive. Modelling therefore offers a logical way forward in assessment of improved management scenario to reduce pesticide runoff to the GBR. Modelling also confers the advantage that it can extrapolate from a relatively small experimental database, to a wider range of conditions and years. The 'Simplified Formula for Indirect Loading caused by runoff' (SFIL) from The Organization for Economic Cooperation and Development (OECD) and the one-dimensional simulation model HowLeaky? are both paddock scale models used for the prediction of pesticide runoff. We tested the applicability of these models to predict paddock scale (edge-of-field) pesticide runoff against experimental data. The experimental data was from two NorthEast Australian sites with three kinds of cotton management, 'conventional', cotton grown in wheat stubble and Polyacrylamide (PAM) added to irrigation water. The simulations were carried out for the eight most frequently detected pesticides. The SFIL-OECD modelled total pesticide loads in runoff were 1.4 to 2.8 times lower than measured loads for various pesticides. The HowLeaky? modelled total pesticide load was 5-23% higher than the measured load using parameter values from the literature. HowLeaky? was able to model similar trends in pesticide concentration compared to measured data following small adjustments to the most sensitive parameters. A sensitivity analysis indicated that the most significant model parameter for the SFIL model was pesticide soil half-life, while for the HowLeaky? model soil half-life, runoff curve number and application rate or efficiency were most significant. The HowLeaky? model was then used to compare pesticide runoff estimates for 'old' (pre-genetically modified cotton) and 'new' pesticides. The rationale for this was that pesticide usage patterns changed significantly with the introduction of genetically modified cotton, particularly with replacement of soil residual herbicides by knockdown herbicides and insecticides with BT cotton. Therefore the pesticide runoff profile has changed accordingly. Comparing the old and new pesticide runoff profiles suggests that use of new pesticides will result in less pesticide runoff in the GBR. This work demonstrates the value of models for predicting the environmental fate of pesticides and thus accessing the amount of pesticide entering streams. Future work will investigate the ecotoxicological implications of a shift in application patterns towards the 'new' pesticides.

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Modelling pesticide runoff from paddocks in the Great Barrier Reef using HowLeaky

Cited by 3 publications

References 7 publications

Pesticide Sustainable Management Practice (Smp) Including Porous Biochar/Geopolymer Structures for Contaminated Water Remediation

Pesticide Sustainable Management Practice (Smp) Including Porous Biochar/Geopolymer Structures for Contaminated Water Remediation

Paddock scale modelling to assess effectiveness of agricultural management practice in improving water quality in the Great Barrier Reef Catchments

Testing two simple pesticide runoff models in Northern Australian agriculture

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