About the base data
Reefonomics uses base data of catchment loads, industry areas and current levels of management practice adoption from the Paddock to Reef program.
For a scenario run, Reefonomics applies ‘actions’ of land management change (the water quality effectiveness is mostly derived from the paddock modelling activities of the Paddock to Reef program) to modify the base data and areas of actions applied, to ultimately predict a water quality improvement from a portfolio of actions.
Each of the key base data sources are described below.
Fine Sediment (FS) and Dissolved Inorganic Nitrogen (DIN)
There are two base load data sets. The first is the benchmark anthropogenic load against which the percentage improvement is derived. This benchmark load is the ‘baseline’ modelled in 2019. The second load data set represents the current (2019) anthropogenic load against which actions are applied. Water quality load data is derived from eWater SOURCE catchment model regional contributor files. The base data represents the anthropogenic load.
River System Delivery Ratio
The SOURCE river system delivery ratio (RSDR) at the planning unit scale is used to scale the DIN and FS so that Reefonomics reports ‘delivery the reef’ changes.
Industry area base
The area to which actions can be applied is defined by the area (or length) to which an action can be applied. That is, in defining an action, the starting (and ending if appropriate) land use that the action targets is defined. In running scenarios, these available areas are critical in determining the maximum available area (or length) that an action could be applied to.
There are 11 base industries (pollution sources) that Actions can be defined to target. Further there are underlying management practices for several industries that can be the target of actions.
Industry (pollution source)
The industry area is extracted from the 2019 SOURCE ‘Change’ scenario regional contributor file.
Industries represented:
- Conservation
- Forestry
- Horticulture
- Urban
- Sugarcane
- Grazing Open
- Grazing Forested
- Cropping Dryland
- Cropping Irrigated
- Banana
- Gully – see below
- Stream bank – see below
- Riparian – see below
Industry practice
The industry practice figures published at the sub-catchment scale for annual report card, as collated by the Department of Agriculture and Fisheries (DAF), are used to as the percentage distribution of different management practices. These sub-catchment management practice proportions are applied across the underlying planning units at the same proportion for all planning units within a sub-catchment.
The industry management practices represented are:
Sugarcane
- Soil management (A-D)
- Nutrient management (A-D)
- Irrigation management (A-D)
Grazing
- Pasture management (A-D)
Cropping
- Soil management (A-D)
- Nutrient management (A-D)
Banana
- Soil management (A-D)
- Nutrient management (A-D)
Stream bank (Grazing)
- Stream bank management (A-D)
Stream bank length
The stream bank length is based on the SOURCE stream layer which reports the total stream length at a planning unit (SOURCE #SC) scale.
Stream bank size
An approximation of overall stream bank length is derived from the SOURCE stream layer. In order to break this value down, the stream length is split into three (small, medium and large) and a scaling of 0.6, 0.3 and 0.1 is applied to approximate the relative proportion of streams of different sizes.
Stream bank load
SOURCE provides an estimate of overall stream bank load. In order to scale this across three stream sizes, scaling is applied, whereby small streams generate 10% per km of medium streams and medium streams generate 10% per km of that generated by large streams.
This approach for proportioning stream size and stream load is a known area needing further research.
Stream bank management practice
The stream bank management practice (A-D) at the sub-catchment scale is that reported by DAF for agricultural practice reporting for the grazing industry. The sub-catchment proportions of stream bank management grades are applied for all planning units within the sub-catchment to get an available length of each grade within each planning unit.
This approach assumes all streams are in grazing lands.
Riparian length
The riparian length is the stream bank length (above) x the 1-percent riparian. The percent riparian is from the 2019 SOURCE parameter files and is represented as a 0-1 value. The result is a planning unit level length of stream that does not have riparian vegetation, and is therefore available to conduct riparian management actions.
The distinction between stream bank length (total stream length) and riparian length is that the grazing stream bank management practices are largely focused on grazing of riparian zones, but do not all consider active fencing and revegetation programs which specifically target areas without riparian vegetation.
Gully length
The gully length is based on the 2019 SOURCE parameter files ‘gully density’ (0-1). The gully density is averaged for grazing industry ( open and closed grazing) for each planning unit and the available gully length is achieved by multiplying the average grazing gully density by the grazing industry area for the planning unit.
Note that this approach does not include gullies in other land uses, notably in conservation areas. The underlying gully load, is the sum of all load from gullies across all land uses, but the available area is only those gullies in the grazing land use.
Gully size
An approximation of overall gully length is derived from SOURCE. In order to break this value down, the gully length is split into three (small, medium and large) and a scaling of 0.6, 0.3 and 0.1 is applied to approximate the relative proportion of gullies of different sizes.
Gully load
SOURCE provides an estimate of overall gully load. In order to scale this across three gully sizes, scaling is applied to whereby small gullies generate 10% per km of medium gullies and medium gullies generate 10% per km of that generated by Large gullies.
This approach for proportioning gully size and gully load is a known area needing further research.
