09 ‎(3)‎

• Board Meeting Date: 11/18/2007
• Description: ISF Section - Increases to ISF Rights, C.R.S. 37-92-102‎(4)‎‎(a)‎
• Board Meetings - Doc Type: Memo

decrease such an appropriation, to preserve the natural environment to a reasonable degree.
The board may adopt conditions attached to an appropriation or decreased appropriation,
may file or withdraw statements of opposition in water court cases, and enter into stipulations
for decrees or other forms of contractual agreements, including enforcement agrecments, that
it determines will preserve the natural environment to a reasonable degree. All contractual
agreements and stipulations entered into by the board prior to May 23, 1996, regarding
enforcement of its appropriations shall be given full force and effect. Any increase to an
existing minimum stream flow or natural lake level appropriation or decree shall be
made as a new appropriation.
Based on the provisions of this statute, staff utilizes the standard new appropriation procedures
set forth in Rule 5 of the Rules Concerning the Colorado Instream Flow and Natural Lake Level
Program (ISF Rules) when evaluating and recommending an increase to an existing ISF
appropriation. To address Board member concerns, Staff requested that the Attorney General's
office provide a legal analysis of the Board's authority regarding this issue. In summary, the
Attorney General concluded:
Section 102(4)(a) recognizes the Board's discretion to decrease or increase its
appropriations of minimum stream flows to preserve the natural environment to a
reasonable degree.
2. Increasing or enlarging an "existing water right" under its decreed priority would not be
possible under Colorado law, and this fact may have given rise to some of the questions
the CWCB staff has encountered. Subsection 104(2)(a) directs the Board to make an
increase or enlargement of an ISF appropriation for a particular stream segment as a new
appropriation which does not require the reopening of any existing water right decree.
Consequently, such ne~v appropriations are more accurately described as an increase or
enlargement to the "appropriation" as opposed to an increase or enlargement to an
"existing water right."
3. The Board may make a new appropriation that increases an existing minimum stream
flow appropriation, with said increase being subject to use in accordance with its new
priority. The Board need only show that it is placing the increased amount of water to a
beneficial use by appropriating such minimum flows between specific points as are
required to preserve the natural environment to a reasonable degree.
2) History of Increases and Biological Analyses
In 1973, the CWCB was vested with the authority to appropriate or acquire water in natural
streams to preserve the natural environment to a reasonable degree. To quantify the amount of
water required for each new appropriation, the Board adopted the Forest Service's newly
developed R2Cross methodology. R2Cross is a hydraulic model used to predict streamflow
based upon a single field transact measurement. The DOW has utilized this method to associate
hydraulic variables with the biologic requirements of cold water fish and generate ``minimum
stream flow" recommendations (Nehring, 1979). The early DOW-modified R2Cross model
generated a single stage "minimum" flow recommendation to maintain food production, egg
incubation and fish passage across a critical riffle in the stream.