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O\)OOOG PRODUCTIVITY for Stream Health classes is defined by a set of ratio-based numerical thresholds that reflect meaningful changes from long-term natural conditions. Using a ratio scale of 0 to 1 has two major 'advantages. First, the field technician is free to select the methods or units of productivity that are the most relevant to the issues. Second, judgements about Stream Health can be based on several measures of productivity that are independent of each other. The ratios are as follows: Robust production ratio range: 1.0 to 0.9 of reference condition. Adequate II II II : <0.9 to 0,7 for legally impacted streams. Diminished II II II <0.9 to 0.7 of reference condition. 1II1JIIired II II II <0.7 to 0,5 II II II Precarious II II II <0.5 to 0,3 II II II Catastrophic II II II <0.3 to 0 II II II Notice that both Adequate and Diminished have the same ratios. Conditions are considered Adequate if - and only if - the reach is part of a sacrifice area taken for some specific management facility such as a road crossing or a range water development or is covered by a CWA S 404 or similar permit; otherwise, it is called Diminished. It is essential that general logging, recreation, mining, grazing, and road construction fully support Robust Stream Health, Stream Health is therefore a combination of Diversity and Productivity; Robust Stream Health for both scales is considered a proper reflection of the CWA goal of physical, chemical, and biological integrity. The combinations are shown in the Stream Health Class Table. The Stream Health Class is determined - from an assessment of the existing conditions measured against its own potential at Robust condition. Each class, either Diversity or Productivity, reflects the decl.ine away from Robust. The class is defined by the lowest of the two dimensions; i.e. Robust Diversity and Diminished production would be declared Diminished Stream Health. The value in using the lowest of the classes is to help define the limiting factor(s) and to better understand restoration as well as prevention of further damage. ============================================================================== Diversity I Health Class 1 -------------1 Robust I Adequate I Diminished 1 Impaired I Precarious I Catastrophic I Table -- Stream Health Classes Productivity (as a ratio of long-term conditions) 1.0-0.9 <.9-0.7 <.9-0.7 <.7-0.5 <.5-0.3 <.3 --------- .-------- --------- .-------- -------- .------- ROBUST ADEQUATE Diminishd Impaired Precarious ADEQUATE ADEQUATE Diminishd Diminishd Impaired Impaired Impaired Precaris precaris precaris Precaris Catastrp Catastrp Catastrp Catastrp Catastrp -------------------> -----------------------------> -----------------------------------------> Catastrph - - - - -- - u - -- - - - - ------- - - - -- - - -- -- -,-- - - -- - - - --- - --> ============================================================================== Text Page 4 ~-,;-'"