The AussieGRASS Environmental Calculator
Australian Grassland and Rangeland Assessment by Spatial Simulation
The AussieGRASS Environmental Calculator, more widely known as ‘AussieGRASS’ (documented by Carter et al. 2000 in ‘Applications of seasonal climate forecasting in agricultural and natural ecosystems’), is an advanced spatial water balance and plant growth model, producing output on a daily time-step across Australia. AussieGRASS, initially built on the point-scale GRASP pasture simulation and water balance model (Rickert, et al. 2000), is run with interpolated climate data (Jeffrey et al. 2001) calibrated using satellite data and pasture biomass observations (Hassett et al. 2000). AussieGRASS was developed with the view of supporting sustainable management of Australia’s rangelands and has been operational on an Australia-wide basis since 1996.
AussieGRASS should be considered a ‘multi-purpose environmental calculator’ and not just a ‘pasture’ simulation model. AussieGRASS is a useful tool for regional analysis, although outputs may not always be accurate at finer spatial scales, particularly for regions with sparse rainfall data. AussieGRASS also provides long-term time series information for specific regions as well as projections for the season ahead.
AussieGRASS was developed using funding from the Land & Water Australia (LWA) Climate Variability Program in collaboration with the major rangeland states and the Northern Territory.
AussieGRASS uses daily climate data from the SILO climate database and calculates pasture growth and other key indicators of the grazing system such as pasture utilisation and ground cover. Calculations are available from 1890 to present.
AussieGRASS is calibrated against more than 600 000 field observations of pasture biomass as well as remotely sensed information from satellites including ground cover and greenness. A range of other information including fire scars, animal production statistics, soil moisture from field and satellite systems, plant nitrogen content, tree litter fall and tree litter data sets are also utilised in calibrating the model.
AussieGRASS was used initially as a regional drought analysis system. AussieGRASS goes beyond a simple analysis of rainfall and calculates important production variables such as pasture growth and pasture biomass. AussieGRASS not only integrates the impact of rainfall and its seasonal distribution, but also the impact of other climate variables such as evaporation and humidity.
AussieGRASS produces indices such as percentile pasture growth, total standing dry matter (TSDM), runoff and rainfall, at time scales of 1-24 months. This information has been an important component of the evidence-based assessment of drought, enabling more efficient and timely use of government funds.
The nature of drought may alter under climate change. AussieGRASS can be used to help rank the severity of future drought events relative to those of the past e.g. the Centennial (1888-89), Federation (1896-1903) and Millennial (2001-2007) droughts.
Example map: chance of exceeding median growth
AussieGRASS provides a platform for translating seasonal climate outlooks into estimates of future plant growth. It is a powerful tool for value-adding to climate information, as it takes into account current condition (e.g. soil moisture, ground cover, nitrogen status and grass basal cover) to provide a probabilistic view of plant growth for the coming three-month period. For example, a high probability of moderate rainfall in the next three months combined with low ground cover, poor perennial plant condition and a currently dry soil profile might lead to little or no plant growth.
Currently, probabilities of pasture growth, runoff (flow to stream) and ground cover are estimated each month for the coming three-month period, with the potential for outlooks of pasture curing index and grass fire risk. At present, AussieGRASS utilises output from the SOI Phase system, to produce short-term pasture outlooks. However DSITI may soon release longer-term outlooks based on Grazing Land Systems experimental SPOTA-1 scheme.
AussieGRASS includes the impacts of total grazing pressure from domestic stock and other herbivores. Land degradation and recovery (documented in Learning from History; McKeon et al. 2004), as well as desertification, are ongoing issues that are likely to be exacerbated by climate change. AussieGRASS calculates pasture utilisation as an index of grazing pressure and takes account of animal consumption in making forecasts of ground cover. AussieGRASS outputs are not only provided on the Long Paddock website, but are also incorporated in various climate risk assessment reports and information systems.
Example map: potential grassfire risk
AussieGRASS calculates monthly estimates of pasture curing state and pasture grass fire risk (a combination of fuel load and curing state). In addition, the model is run every night to provide daily estimates of the biomass of fuel components (green grass, dead grass, grass litter and tree litter). These estimates are available for use by rural fire agencies in GIS based systems. Estimates of total standing dry matter for the coming three-month period are available on application.
Example graph: Annual growth by sub-IBRA region
Putting current conditions into a historical perspective and providing the elements of a DPSIR framework: Drivers (climate), Pressure (grazing pressure), State (biomass, ground cover), Impact (pasture utilisation, erosion); and Response (stocking rate change) for grazing lands, provides a solid basis for reporting and describing environmental change under the influence of a variable and changing climate.
AussieGRASS outputs are used by the Australian Collaborative Rangelands Information System (ACRIS) to provide analysis of trends in rangelands. AussieGRASS outputs are also used in Queensland State of Environment reporting. Information can be generated at national and state scales and also for specific regions (e.g. Interim Biogeographic Regionalisation for Australia (IBRA and subIBRA) regions. Time series graphs (annual from 1890 and monthly from 1990) of rainfall, minimum and maximum temperature, evaporation, pasture growth and biomass are available as regularly updated products at the subIBRA scale.
AussieGRASS has also been used for obtaining broad scale estimates of greenhouse gas fluxes. AussieGRASS has an expanding capability to estimate rangeland emissions and carbon stocks. Methane fluxes from livestock, fire, termites and soil uptake can be estimated on a daily basis.
AussieGRASS outputs are also being increasingly used for various environmental analyses, for example, estimating plant net primary production for soil carbon mapping, providing soil moisture as an initial condition for air pollution models, analysing how stock numbers influence the potential amount of biomass which can be burnt, analysing conditions suitable for dust storms and estimating the impact of removing tree cover on deep soil water infiltration.
Daily climate projections data for 2030 and 2050 are being produced by Grazing Lands Systems' Consistent Climate Scenario’s project. When incorporated in the AussieGRASS modelling framework, this information will enable climate change impacts on pasture production and livestock carrying capacity to be readily assessed.
The effects of CO2 on plant transpiration efficiency and other functional parameters are included in GRASP, as is the impact of increases in the sub-daily rainfall intensity on soil erosion.
There are three guides available to provide support for AussieGRASS products:
- The “AussieGRASS Product Guide (PDF, 3.5M, last updated 01:58PM, 25 June 2015)*” provides a semi-technical overview of the major operational products from the AussieGRASS system. It contains descriptions of various AussieGRASS outputs, how they are calculated and importantly the caveats applying to these products.
- The “AussieGRASS User Guide (PDF, 6.0M, last updated 01:58PM, 25 June 2015)*” provides tutorial information for use of the AussieGRASS products to interpret maps, graphs and other analyses – with emphasis on SubIBRA timeseries and map usage.
- The "AussieGRASS Metadata Guide (PDF, 602K, last updated 03:19PM, 10 June 2016)*” is an information source to provide AussieGRASS GIS users (internal and external) with ‘need to know’ details to assist data manipulation and product analysis.
The Publications page lists a range of publications related to AussieGRASS.
To enquire about access to ‘premium’ AussieGRASS products, please visit the AussieGRASS Contacts page.
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Last updated 10 June 2016