Big Hole River grayling: Big Hole Watershed Committee fails

Today's grayling survival index is -92.5, based on a flow at Wisdom (see http://waterdata.usgs.gov/mt/nwis/uv?06024450) of 23 cfs (cubic feet per second). [see below for explanation of the grayling survival index calculation]

The Big Hole Watershed Committee's so-called "Drought Management Plan" mandates an arbitrarily defined 20 cfs as the level at which voluntary sanctions kick in. Flows declined rapidly and then held steady just above 20 cfs. This appears to be a cynical effort to keep flows above the sanction trigger level, while maintaining flows that are so low that there is no biological evidence that they support even minimal grayling survival.

Many people responded to the photos on last week's post (Friday, June 22, 2007). Most were very supportive and expressed their outrage and concern. A few thought I was being too hard on ranchers, and ought not to make a public issue of this. My response: (1) I do not intend to criticize any individual.* My criticism is aimed at the myth that the Big Hole Watershed Committee successfully manages water for grayling; and (2) Public criticism is absolutely necessary. The Big Hole Watershed Committee has received millions of dollars in federal funding, and yet the group is not held accountable for demonstrating any outcomes based on this federal funding.

* As I explained in my book Montana's Last Best River: The Big Hole River and its People (Lyons Press, 2001), there are some individual ranchers that take extraordinary measures and sacrifice their own bottom line to support grayling. Unfortunately, the heroic efforts of these few individuals have simply been inadequate to deal with dewatering and habitat damage on a landscape level (the river at Wisdom drains about 575 square miles, or about 360,000 acres).

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EXPLANATION OF THE GRAYLING SURVIVAL INDEX:
Less than 0 means a loss of grayling; 0 means minimum sustainable level; 100 means maximum survival.For this blog, the flow of the Big Hole River at Wisdom, Montana, provides an index of how well the Big Hole Watershed Committee is doing in its efforts toward water conservation and grayling restoration. Today, the Watershed Committee is doing a lousy job.

According to fisheries biologists, the upper wetted perimeter at Wisdom is 160 cfs (cubic feet per second). The lower wetted perimeter is 60 cfs. The minimum "survival flow" is 20 cfs. This "survival flow" is not scientifically based, but it is the flow level that fisheries biologists "feel" allows grayling the ability to escape warm water and to seek cold water refugia (tributary streams).

Criteria for grayling survival index ratings:*
At 160 cfs, grayling recruitment and survival is rated at 100. At this level, the streambed is fully wetted or bank-full. This level allows grayling the maximum use of stream "pasture" for foraging, hiding, spawning, etc. This level maximizes grayling recovery.*
At 60 cfs, grayling recruitment and survival is rated at 0. At this level, the streambed is minimally wetted. This level allows grayling to maintain their population. This level does not aid in the recovery or increase of the grayling population. At best, this level might maintain the current population level. Below this level, the streambed rapidly becomes dry and thus barren of aquatic life.*

At 20 cfs, grayling recruitment and survival will be rated at -100. At this level, some grayling will be able to move to cold water refugia (tributaries), but many will perish due to lack of cover, exposure to predators (such as pelicans), and high water temperatures. For stream flows above 60 cfs, the grayling survival index = y = mx + b = x - 60. For stream flows below 60 cfs, the grayling survival index = y = mx + b = 2.5x - 150. Thus, today's grayling survival index = 2.5(23) - 150) = -92.5.