Select Assessment Framework
Prior to assessing stream health and evaluating how well a river delivers services to communities, select a framework to prioritize, organize, and characterize data. The assessment framework should:
Frameworks can go beyond taking a snapshot of existing conditions to also consider change, both natural and human-influenced. They can measure degrees of departure from some expected or desired state, or from a natural “reference” condition. Analysis of change can look at the past (e.g., reservoirs built that impact flow and other stream health variables, but deliver important water storage services) or the future (e.g., increasing water demand, changing land uses, or temperature increases).
Organizing Framework: FACStream/COSHAF
The Yampa River Health Assessment and Streamflow Management Plan used an adaptation of FACStream 1.0, the Functional Assessment of Colorado Streams (FACStream). This is a reach-scale assessment tool that rates stream health according to the degree of impairment of several ecological variables.
The framework’s organizational methodology is detailed in Appendix B of the Yampa River Health and Streamflow Management Plan. Core drivers of Yampa River health, represented by 11 variables, were studied for five sub-reaches within the project extent. Each reach, and each variable within each reach, was graded using an academic (A-F) grade that indicates the degree of impairment from the natural state. Possible stressors and likely causes of impairment were also provided.
A number of SMPs to date (Crystal, Roaring Fork, San Miguel, Eagle, Middle Colorado, St. Vrain and Left Hand, Big Thompson, and South Boulder Creek) have used some form of this assessment framework to organize their data. The Colorado Stream Health Assessment Framework (COSHAF) is a recent iteration of the FACStream methodology that can be customized to a particular stream or watershed and has been used as an assessment tool for several SMPs. The Colorado Basin Roundtable developed a framework for IWMPs that builds on COSHAF by including variables related to consumptive water use needs.
The St. Vrain and Left Hand Stream Management Plan applied the COSHAF methodology to their watershed. Instead of letter grades, low to very high ecological risk categories were used to present their evaluations of each indicator variable for the reaches in their study area. The ecological risk categories were derived from the CWCB’s 2019 Flow Evaluation Tool. Presenting assessment results in terms of risk in lieu of letter grades for Phase 1 of their SMP facilitated simpler stakeholder conversations around the St. Vrain and Left Hand SMP.
Organizing Framework: Series of maps and graphics
Rather than using a scoring framework, the Upper Gunnison developed a series of maps illustrating the locations of several variables (urban and industrial areas and their estimated water use; irrigation structure locations and diversions; important recreation areas; healthy and impaired river segments; calling structures/compacts under different flows; location of dry-up points under different flows; projected changes in temperature and precipitation) and graphs of modeled streamflow conditions.
The maps and graphs were used to generate a list of approximately 15 priority locations for more in-depth stream surveys.
Left Hand Creek: Building Watershed Resilience Through Adaptive Management
Organizing Framework: Comparison to potential future conditions
Another potential organizing framework for SMPs is the Left Hand watershed’s conceptual model, which compares existing conditions to a desired future condition.
The Left Hand Watershed Center’s (LHWC) adaptive management guide provides a useful and relatively detailed conceptual model that can be used as a resource to understand and define stakeholders’ vision of watershed health and resilience. The conceptual model includes illustrations and descriptions of different watershed zones (canyons, alluvial fan, high plains) through time (pre-flood, post-flood, restoration, desired potential future condition), depicting how the watershed has changed over time and illustrating a trajectory toward resilience. The model tracks the trajectory toward resilience through monitoring key watershed functions, identified by LHWC as:
Flow Regime (water quantity, timing, and floodplain connection)
Stream Form (physical stream channel, including channel dimensions, gradient, and lateral and bank stability)
Sediment Regime (sediment, including bed structure, sources, and transport)
Ecological Community (aquatic and riparian habitat and biological communities)