Fundamental ecological concepts are the foundation for each health index. Consistent steps are taken to progress from the identification of important ecological concepts to the delivery of a health index value by watershed:
Review scientific literature to inform the selection of significant and well-supported ecological relationships
Review availability of statewide GIS data that support the selected relationship.
Suitable GIS data must be:
- Temporally stable
- Likely to be repeated
- Consistently collected statewide
- Appropriate resolution for Major Watershed scale calculations
Discuss index development approaches with subject matter experts
Compute results by applying an appropriate GIS method, such as:
- Advanced modeling techniques
- Quantification of comparable values
- Density of features
Rank and score results
- Review results and range of values
- Set threshold values for scores when available and appropriate
- Assign "0-100" health scores based on the calculated range of values; or based on a range of known ecological conditions