How does it work?
The science behind the Report indicates that habitat conditions vary depending on two measurable factors: streamflow volume and the passage of time. The entire methodology and the science used for selecting the reference fish community, determining each species habitat conditions, and ultimately the setting of "optimal" streamflow thresholds and continuous days duration below thesholds is too lengthy to discuss here. But it is interesting and you are encouraged to explore it in depth by clicking on the link above.
The "Signal" of the meter on any given day will be either Green, Yellow, Red or N/A signifying either Normal, Dangerous, or Catastrophic habitat conditions on the river. An N/A indicates data was not available that day. The Report states that Green signals represent normal streamflow conditions. Under Yellow signals voluntary steps to conserve water should be undertaken by the Watershed community. Under Red conditions mandatory conservation measures are recommended.
The meter also displays a "Level" indicator that is either Blank, 1, 2 or 3. The Level is indicative of habitat conditions relative to streamflow thresholds that occur in the common course of annual cycles (Level 1), of more restrictive habitat conditions as determined by low streamflow thresholds (Level 2), or of seriously low streamflows that dramatically impact habitat (Level 3). If the Level is Blank it indicates that streamflow volume is above the highest threshold set at Level 1.
In combination, Red Level 2 & 3 conditons drastically diminish habitat and should not occur more often than once every decade.
Each Level has an associated days duration counter (or "clock" as we like to call it), as well as three threshold parameters that vary depending on which Bioperiod for fish fauna is currently in effect: a Base Flow threshold, a Persistent Days Duration threshold and a Catastrophic Days Duration threshold. The clock keeps a tally of the number of consecutive days the USGS dishcharge flow guage has been below the Base Flow threshold for a given Level. When the clock count meets or exceeds the Persistent Days Duration threshold a Yellow conditon is generated. If the clock continues on to meet or exceed the Catastrophic Days Duration threshold a Red conditon is generated. The Habitat Meter scans all three Levels for the most serious case, and uses it for the signal. In order to reset the clock there must be two consecutive days where the actual streamflow equals or exceeds the Base Flow threshold. On the first such day, the clock is merely trimmed in half. |
