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

Office Procedures
The CWCB uses a Lotus 1-2-3 macro,
called R2CROSS, to process the field data and
model instream hydraulic parameters at
streamflows above and below the field-
measured discharge. The CWCB relies upon
the biologic expertise of the cooperating
agencies to interpret the output from R2CROSS
and develop an initial, biologic instream flow
recommendation. This initial recommendation
is designed to address the unique biologic
requirements of each stream without regard to
water availability. After receiving the
cooperating agencies' biologic recommendation,
the CWCB staff evaluates stream hydrology to
determine whether water is physically available
for an instream flow appropriation.

Backil"ound on the R2CROSS Methodoloey
Three instream hydraulic parameters,
average depth (x d)' average velocity (xy)' and
percent wetted perimeter (% WP), are used to
develop biologic instream flow
recommendations in Colorado. The DOW has
determined that by maintaining these three
hydraulic parameters at adequate levels across
riffle habitat-types, aquatic habitat in pools and
runs will also be maintained for most life stages
of fish and aquatic invertebrates (Nehring
1979).
The R2CROSS methodology uses
Manning's equation to predict xd' xv' %WP,
and other instream hydraulic parameters, at
discharges both above and below the field-
measured stream discharge. The methodology
is both time and labor efficient, requires data
from only a single stream transect, and has been
found to produce similar results to more data
intensive techniques (Nehring 1979) such as the
Instream Flow Incremental Methodology
(IFW) developed by the U.S. Fish and Wildlife
Service (Bovee 1982).
In 1973, the CWCB staff performed all
Manning's equation calculations with a hand-

held calculator. In 1981, the USFS released
"Program Documentation for Rl-CROSS-81"
(Weatherred et ale 1981). This Fortran-based,
mainframe computer program automated the
repetitive task of manipulating and
recalculating Manning's equation by hand The
CWCB used the USFS version ofR2CROSS on
the Colorado State University mainframe
computer until 1985.
In 1986, the CWCB staff began
development of a personal computer version of
R2CROSS using the macro capabilities of
Lotus 1-2-3. The CWCB found the R2CROSS
macro to be advantageous because it ran on a
personal computer and it could be customized
to the specific needs of the CWCB. The most
recent version of R2CROSS is menu-driven
(Figure D) and requires very little experience
with Lotus 1-2-3. The macro formats the
R2CROSS worksheet, initiates data entry, and
performs all calculations and printing
automatically.
Figures E through K provide an example
of R2CROSS output from a typical Colorado
stream. Figure E is a "Proof Sheet" that is
printed and inspected for data entry errors prior
to performing final R2CROSS c3Iculations.
Fmal output consists of a five page printout
(Figures F through J). Page one summarizes
most of the stream location information,
supplemental data, and channel profile data
from the field form (Figure F). Page two
summarizes the channel geometry/discharge
field data set and values computed from the raw
field ~ including an estimate of Manning's
"n" (Figure G). Page three consists of a water
line comparison table which the program uses
to interpolate the single water surface elevation
that results in a calculated cross-sectional area
equal to the field-measured cross-sectional area
(Figure H). Page four is the staging table that is
used by the cooperating agency to develop an
initial, biologic instream flow recommendation

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