WSP01154

• File Number: 8062
• Description: Federal Reserved Water Rights
• State: CO
• Basin: Statewide
• Date: 3/1/1995
• Author: USDOC
• Title: Instream Flow Incremental Methodology - A Primer for IFIM
• Water Supply Pro - Doc Type: Report/Study

6 BIOLOGICAL REpORT 29

population and, more importantly, determines the
number of adults available to the fIshery on an
annual basis. To illustrate this point, we must
combine the habitat functions and hydrologic time
series into a quasi population analysis by display-
ing habitat quality and quantity through time and
space, The IFIM methodology translates the base-
line hydrology into a description of the available or
usable habitat present during that historical pe-
riod, This description is often called the resource
benchmark, from which fishery scientists identify
enhancements and impacts resulting from pro-
posed water delivery schedules,
By examining recent historical conditions (say
the last 5-10 years) using the power of computer
simulation, it is possible to calibrate a system
model using historical data such as annual popula-
tion indices and trend information, creel census
information. computed year-class strength data
from age and growth studies, or anecdotal informa-
tion on the general well.being offish populations in
one year versus another, If the fishery manager can
show that a simulated habitat analysis over a 10-
20'year historical hydrologic regime agrees with
historical information On good' years versus poor
years in the fishery, much more credence can be
placed in those models for comparing \'arious alter-
native futures.
IFIM has been designed for river system man-
agement by providing an organizational framework
for evaluating and fonnulating alternative water
management options, It has been built on the philo-
sophical foundation of hydrological analyses to un-
derstand the limits of water supply, Analysis offers
a description, evaluation, and comparative display
of water use throughout a river system Emphasis
is placed on the display of usable habitat acroSS
several years to capture the variability in both
water supply and habitat. Such comparative infor-
mation enhances negotiations in the planning and
management of the riverine resources. Sharing
limited water during drought cycles and the man-
agement of timed releases contribute to compatibil-
ity between instream and out-or-stream user
groups and allow for rapid recovery ofaquatic popu.
lations during favorable conditions,
We are oft.en asked to provide cost estimates for
conducting an IFIM study, One might say that
about 80% of IFIM studies for a single river seg-
ment could be conducted within a 12.month time
frame and cost less than $45,000. But "it depends.
is probably the best answer, it depends on
how many variables are included in the various

models, the sampling strategy, the standards for
quality assurance and quality control, the size of
the river and accessibility of the physical site, the
experience of those performing the work, the nwn-
ber of alternatives to be analyzed, and the number
of times Murphy meddled from start to finish. A
careful scoping is always in order before proceed-
mg.

Extending IFIM Into the
Future

Reiser et aL (989) surveyed IFIM users and.
found that the highest priority research needs are' ,
to (I) define the relation between flow, habitat,
and fish production; (2) validate and test the rela-
tion of habitat measurements to fish production;
and (3) de"elop new methods for determining flow
requirements, Contemporary research (Hagar
et aL 1988; Cheslak and Jacobson 1990; Auble
et aL 1991; EA Engineering, Science and Technol-
ogy 1991; Nehring and Anderson 1993; William.
son et aL 1993) is broadening the role ofIF1M to
provide fisheries management as well as habitat
management capabilities,
The relation between flow, habitat, and fish pro.
duction is based on work relating the amount and
quality of habitat available to the fish population
at critical stages in its life history (Bums 1971;
Mundie and Traber 1983; Morhardt and Mesick
1988), In riverine systems the amount and quantity
of suitable habitat can be highly variable within
and among years. At any time, the observed popu-
lation and biomass of fis!: may be influenced (de.
pressed or stimulated) by many preceding habitat
events. Long,term habitat reductions from reduced
flows may also be important in determining the fish
population and production (Bovee 1988), National
BiolOgical Service scientists are testing models of
these new concepts on anadromous salmonid popu.
lations in California and resident trout populations
in Colorado (Bartholow and Waddle 1994;
Bartholow et ai, 1993).
Goals of contemporary research are (1) devel-
opment and validation of a dynamic fishery popu-
lation model, including response to. flow-related
limiting events, specifically physical habitat and
temperature; (2) testing of habitat bottleneck hy- .
potheses; (3) development of processes for evalu.
ating water managemen~ strategies to achieve
fish population objectives; (4) testing of strategies
for long.term population support including bi-
otic interactions; and (5) improvement to those