7926

• UCREFRP Catalog Number: 7926
• Author: Annear, T. C. and A. L. Conder.
• Title: Relative Bias of Several Fisheries Instream Flow Methods.
• USFW Year: n.d.
• USFW - Doc Type: Cheyenne, Wyoming.
• Copyright Material: NO

the 13 streams (Table 5).

All three of the biased recommendations were b

low, however, none of these recommendations was grossly less than the

value of the MF range (1.2 cfs vs. 1.6 cfs, 3.6 cfs vs. 3.9 cfs, 13 cfs

cfs). Consequently, this method may provide a generally safe starting point for

developing instream flow recommendations.

The primary limitations of this

method are that (1) it is incapable of quantifying biological trade-offs for

mitigation and (2) it incorporates no site-specific biological or hydrological

information in the decision-making process. Other methods should be considered

where this type of information is necessary.

Ten percent AF was intended by Tennant as a short-term minimum flow. How-

ever, this recommendation has been taken out of context by some who have used

it in a more general sense. We found that estimates from this method were con-

sistently among the lowest of all methods included in this study. All 13 of the

recommendations using this method were biased low which suggests a high risk of

underestimating instream flow needs for trout.

Wetted Perimeter

None of the methods in this category generated a significant number of

unbiased MF estimates.

Both subjective methods provided estimates that were

biased upwards (P(O.OS) when nonbiased estimates were not generated. This may

be acceptable in some cases as, if the recommendation were to be found ~n error

at a later date, it would be preferable to overestimate than underestimate flow

needs. This creates the flexibility to negotiate downwards after making preli-

ffilnary recommendations, which may be easier than negotiating for higher flows.

I
however I that t.hree of the six upwards-biased MF eS timates for both

9

!!~-:-)