Friday, June 22, 2007

Big Hole River grayling survival index GOES NEGATIVE (22June07)

Today's grayling survival index is -25, based on a flow at Wisdom (see of 50 cfs (cubic feet per second). [see below for explanation of the grayling survival index calculation]
Flows in the upper river have dropped like a rock, despite wetter-than-normal weather. Cattle are standing in water on the irrigated hay meadows while grayling die for lack of water.

A cow fording a flooded hay meadow near Wisdom:
This is not a creek--this is a flooded place in an irrigated hay meadow. Cattle are drowning while grayling are going extinct. Where is the Big Hole Watershed Committee? What about the group's so-called "Drought Management Plan?"

Cattle in a flooded pasture near Wisdom:
Also, note the dead willow clump to the right of the cow facing the camera. Is this wise use of water?

Cattle along an overgrazed, collapsing, eroded bank on a creek near Wisdom:
These ruined banks cause the creek to become wider, shallower, and warmer. They cause siltation of the streambed. This is on a creek that FWP biologists say is a refuge for grayling when the river becomes too low and warm. THIS IS WHY BIG HOLE RIVER GRAYLING ARE GOING EXTINCT.

Noah Greenwald of the Center for Biological Diversity toured the Big Hole with me yesterday. He was appalled to see flooded hay meadows and cattle wading through water while the Big Hole River flows are below survival levels for grayling. So much for the Big Hole Watershed Committee's ability to gain cooperation for water conservation.


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(50) - 150) = -25.


Anonymous said...

I work at the Montana DEQ. Could I get permission from you to use the eroding banks photo above?

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