ISFAPP01508

• Year: 1996
• Title: Development of Instream Flow Recommendations in Colorado Using R2CROSSDevelopment of Instream Flow Recommendations in Colorado Using R2CROSS
• CWCB Section: Stream & Lake Protection
• Author: Gregory D. Espegren
• Description: Overview of Colorado's ISF Program and documentation for the R2CROSS Lotus macro
• Publications - Doc Type: Historical

Executive Director of the Department of
Natural Resources, the Directors of the CWCB
and DOW, the State Attorney General, and the
State Engineer. The diverse backgrounds of its
board members provides the CWCB with an
excellent representation of Colorado's various
water interests.
Colorado's InstreamFlow Program was
created in 1973 when the Colorado State
Legislature recognized "the need to correlate
the activities of mankind with some reasonable
preservation of the natural environment"
through the passage of SB 97. Within SB 97,
the defmition of beneficial use was changed to
include minimum stream flows and the CWCB
was vested with the authority to appropriate
"waters of natural streams and lakes ... as may
be required ... to preserve the natural
environment to a reasonable degree." SB 97
was amended by Senate Bill 414 in 1981,
Senate Bill 91 in 1986, Senate Bill 212 in 1987,
and Senate Bill 54 in 1994. These changes and
amendments are consolidated wi~ ~ 37-92-
102(3), C.R.S. (1990), the Instream Flow
statute.
The Instream Flow statute sets forth the
guidelines for the admini~tration of Colorado's
Instream Flow Program. The statute vests the
CWCB with the exclusive authority to
appropriate and acquire instream flow and
natural lake level water rights. In order to
encourage other entities to participate in
Colorado's Instream Flow Program, the statute
directs the CWCB to request instream flow
recommendations from other state and federal
agencies prior to initiating an instream flow
appropriation. The CWCB routinely requests
in stream flow recommendations from the
row, Colorado Division of Parks and Outdoor
Recreation, United States Department of
Agriculture, and United States Department of
Interior (the "cooperating agencies").
Prior to appropriating an instream flow
water right, the statute requires the CWCB to:

(1) "determine that the natural environment will
be preserved to a reasonable degree by the
water available for the appropriation to be
made; (2) determine that there is a natural
environment that can be preserved to a
reasonable degree with the CWCB's water right,
if granted; and (3) determine that such
environment can exist without material injury to
water rights" (~37-92-102(3c), C.R.S. (1990)).
The CWCB makes these determinations based
upon a review of the supporting technical data
and a final instream flow recommendation
prepared by the CWCB staff.
Standardized field and office procedures
have been developed to help ensure that final
instream flow recommendations meet statutory
guidelines and are consistent. The standard
field procedures that were established concern
selection of transect sites and collection of
hydraulic and biologic data Standard office
procedures have been established for
determining biological instream flow
recommendations using output fi'Qm R2CROSS
and for analyzing water availability.

Field Procedures
Instream flow recommendations are
typically based on hydraulic and biologic data
collected during a single field visit. Hydraulic
data collection consists of setting up a transect,
surveying stream channel geometry, and
measuring stream discharge. Biologic data is
gathered to document the existence of a natural
environment. The biologic data usually
consists of a fish sample, collected by
electroflShing, and an aquatic invertebrate
sample.

Field Data Site Selection
The R2CROSS method requires that
stream discharge and channel profile data be
collected in a riffle stream habitat-type. A riffle
is a stream segment that is controlled by
channel geometry rather than a downstream

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