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TitleMacroinvertebrate condition sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which assesses the macroinvertebrate condition for rivers according to its macroinvertebrate O/E ranking, abstraction and flow variability.
Input data
Lineage
Macroinvertebrate condition was determined using an expert rule system under the guidance of experts from Freshwater Systems (consultants) and the Department of Primary of Industries and Water (see ‘Assigning values to ecosystem spatial units’ below). Information on expert rules systems can be found in Appendix 3 of the CFEV Project Technical Report. The input variables to this expert rule system were:
Macroinvertebrate O/Erk bands were used to indicate the degree of change in community composition at the family level (relative to pre-European settlement conditions - see section below). The flow abstraction index was used as an indicator of the degree of habitat loss from flow reduction. The flow variability index was used as an indicator of the reduction in habitat stability and macroinvertebrate mortality due to changes in flow variability at a range of time scales. Both increases in variability (daily hydro electric releases) or decreases in variability, (dams removing daily/weekly/monthly flow events) can be deleterious.
The definition table for the expert rule system (see ‘Assigning values to ecosystem spatial units’ below) weights the inputs in order of influence as abstraction index > macroinvertebrate O/E > flow variability index. This macroinvertebrate condition sub-index was used as an input for the biological condition expert rule system.
The method for assigning a macroinvertebrate condition sub-index score to the river spatial units is provided below.
Date createdApril 2005
Scale and coverage1:25 000; Statewide
Column headingRS_BUGCO
Type of dataContinuous but has been converted to categorical format (see Table 2).
Number of classes5
Assigning values to ecosystem spatial units
A macroinvertebrate condition sub-index score (0 = poor condition – 1 = good condition) was assigned to river spatial units as RS_BUGCO using the expert rule system shown as a definition table in Table 1 (e.g. if the river has a HIGH score for macroinvertebrate O/E, LOW score for abstraction and a HIGH score for flow variability, then assign a score of 0.3). Using fuzzy logic enables input data and output results to be continuous rather than categorical as implied here (i.e. inputs and output data can range on a continuous scale between 0 and 1, and the process of executing the expert rule system will determine its membership as being HIGH or LOW) (refer to Appendix 3 of the CFEV Project Technical Report for more information on expert rules systems).
Table 1. Expert rule system definition table for the macroinvertebrate condition sub-index for rivers.
Macroinvertebrate O/Erk (RS_BUGSOE) | Abstraction index (RS_ABSTI) | Flow variability (RS_FLOVI) | Macroinvertebrate condition score (RS_BUGCO) |
H | H | H | 1 |
H | H | L | 0.6 |
H | L | H | 0.3 |
H | L | L | 0.2 |
L | H | H | 0.5 |
L | L | H | 0.1 |
L | H | L | 0.4 |
L | L | L | 0 |
The rivers spatial data layer has the continuous macroinvertebrate condition sub-index data categorised according to Table 2. The categorical data was used for reporting and mapping purposes.
Table 2. Macroinvertebrate condition categories for rivers.
Category | Min to max values |
1 | 0 to <0.2 |
2 | 0.2 to <0.4 |
3 | 0.4 to <0.8 |
4 | 0.8 to <1 |
5 | 1 |
CFEV assessment framework hierarchy