The foundation of a healthy watersheds assessment is compilation of ecological information that is measurable, comparable and consistent across the area of the assessment, and relevant to summarizing the primary attributes of a watershed’s condition. Watershed indicators are first selected, based on the six essential ecological attributes fundamental to the healthy watersheds assessment approach:

• Landscape Condition
• Habitat
• Hydrology
• Geomorphology
• Water Quality
• Biological Condition

A sub-index for each of the six attributes is developed from these indicators. Sub-index values for each watershed are then aggregated up into a single Watershed Health Index value for each watershed.

All sub-index and index values are relative (i.e., "healthier" or "less healthy" as compared to the group of watersheds being assessed). These values are not absolute (i.e., no cutoff value for health is identified). Index and sub-index values are meant for comparing relative differences among watersheds rather than precisely defining healthy vs. unhealthy watersheds.