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TitleWetland hydrology sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which assesses the hydrology for wetlands according to impacts associated with catchment disturbance and abstraction.
Input data
Lineage
The hydrology variable was created using an expert rule system that included input data to describe impacts associated with catchment disturbance (land clearance and intensive land use practices) and an abstraction index (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. It was considered by experts that catchment disturbance had more of an influence on hydrology than abstraction.
The method for assigning a hydrology sub-index score to the wetlands spatial units, using definition tables developed for the expert rules systems, is provided below.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
Column headingWL_HYDRO
Type of dataContinuous but has been converted to categorical format (see Table 2).
Number of classes5
Assigning values to ecosystem spatial units
A hydrology sub-index score (0 = poor condition – 1 = good condition) was assigned to wetland spatial units as WL_HYDRO using the expert rule system shown as a definition table in Table 1 (e.g. if the wetland has a HIGH score for abstraction and a LOW score for catchment disturbance, then assign a score of 0.2). 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 hydrology sub-index for wetlands.
Abstraction index (WL_ABSTI) | Catchment disturbance (WL_CATDI) | Hydrology score (WL_HYDRO) |
H | H | 1 |
H | L | 0.2 |
L | H | 0.3 |
L | L | 0 |
The wetlands spatial data layer has the continuous hydrology sub-index data categorised according to Table 2. The categorical data was used for reporting and mapping purposes.
Table 2. Hydrology sub-index categories for wetlands.
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