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

Introduction

Colorado's Instream Flow Program
originated in 1973 with the passage of Senate
Bill 97 (SB 97). Under SB 97, the Colorado
Water Conservation Board (CWCB) was vested
with the authority to appropriate instream flow
water rights in the State of Colorado (A 37-92-
102(3), C.R.S. (1990)). Instream flow water
rights are held by the CWCB on behalf of the
people of the State of Colorado to "preserve the
natural environment to a reasonable degree."
Today, the CWCB holds 1,326 instream flow
water rights covering approximately 7 ~982
miles of Colorado streams.
Determining the quantity of water
required to preserve the natural environment to
a reasonable degree can be a difficult task. The
CWCB, in cooperation with the Colorado
Division of Wildlife (DOW), has developed
standard field and office procedures to ensure
that each instream flow. appropriation is
necessary and reasonable and that the amount of
water recommended is available for
appropriation.
The R2CROSS methodology described
in this document is a valuable tool in
developing these instream flow

recommendations. The CWCB uses R2CROSS
because it is time and labor efficient and
produces results which are comparable to more
data intensive techniques (Nehring 1979).
This manuscript is divided into two
sections. The first section describes Colorado's
Instream Flow Program, including some of the
statutory guidelines that have shaped the
program. It also describes the standard field
techniques and office procedures that are used
by the CWCB staff in the development of
R2CROSS-based instream flow
recommendations. This section is intended to
provide an understanding of the procedural and
technical aspects of Colorado's Instream Flow
Program.
The second section of the manuscript is
a users' manual for the CWCB's R2CROSS
macro. The CWCB has received many requests
for i~ R2CROSS macro from both the public
and private sectors but has been hesitant to
release the program without proper
documentation. The second section of the
manuscript is intended to provide that
documentation.

Colorado's Instream Flow Program

Instream Flow Legislation
The CWCB was created in 1937 to
serve as the State's chief water planning agency
(~ 37-60-101 through 123, C.R.S. (1990)).
Today, the CWCB is responsible for the
administration of the State's Instream Flow
Program, protection of endangered aquatic
species, identification of flood plains, funding
of new water development and water

conservation projects, and negotiation of inter-
and intra-state water planning issues.
The CWCB is a fourteen-member board
The board consists of one Governor-appointee
from each of the eight major river drainages in
the State and one from the City and County of
Denver. Each Governor-appointee must also be
coofmned by the Colorado State Senate. Ex-
officio members of the board include the

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