DEMONSTRATION FLOW ASSESSMENT: PROCEDURES FOR DIRECT OBSERVATION INSTREAM FLOW STUDIES Short title: DEMONSTRATION FLOW ASSESSMENT PROCEDURES

The Demonstration Flow Assessment (DFA) method for instream flow evaluation uses direct observation of river habitat conditions at several flows and expert judgement to rank the alternative flows. The DFA method has the advantage of allowing long river reaches to be assessed at relatively modest cost. However, past applications have often lacked procedures and documentation to assure that results are reproducible and reasonably free of uncertainty and bias. This paper provides procedures to make DFA instream flow studies more credible and defensible while keeping study costs low. The procedures combine established concepts from stream ecology and decision analysis, and are general and adaptable to a variety of sites. Approaches are recommended for studies targeting both a few particular species or the general integrity of the aquatic community, and could be adapted for assessment of flow needs for other resources such as recreation and aesthetics. The procedures use “habitat quantification”: specific types of important habitat are defined and then quantified in the field during demonstration flows. The five major steps are: (1) Decision framing, establishing the fundamental assumptions, constraints, and expectations for the instream flow assessment; (2) Conceptual modeling, developing high-level mechanistic, empirical, or theoretical/community models for how flow affects fish by affecting food production, feeding, mortality risks, or reproduction; (3) Metric development, defining specific, measurable habitat types to be quantified; (4) Field observations, quantifying the area of each habitat type at each demonstration flow, using visual estimation aided by detailed maps and other tools; and (5) Analysis, calculating the total area of each habitat type for each demonstration flows, then ranking flows according to habitat benefits and resource tradeoffs. A study that used procedures similar to these recommendations to evaluate instream flows for salmon spawning and rearing is presented as an example.