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

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Due to the magnitude of the task, the resources available and other policy considerations, the majority of
the CDOW's instream flow recommendations were based only on the Level 1 Single Transect R2X
Method. The CDOW and CWCB have continued to use the R2X Method because it has been adaptable •
to the evolving instream flow science and changing values and policies of the people of Colorado. R2X
has also proven to have a very high benefit to cost ratio. Using R2X, CDOW and others have been able
to collect a significant amount of stream specific data on a large number of Colorado's stream miles for
a reasonable cost.
In addition, because the State of Colorado is a prior appropriation state and "first in time means first in
right", using the R2X Methodology has allowed the CWCB to adjudicate more instream flow water
rights sooner than other methodologies would have allowed. The sooner an instream flow water right
could be adjudicated, the greater likelihood there would be of having water available for protection of
aquatic environments. This decision allowed the CDOW and CWCB to achieve some baseline
protection on a significant portion of Colorado streams before other junior water rights appropriated the
remaining physically available stream flow. To put this in perspective, in the late 70's and early 80's, the
CDOW was recommending and the CWCB Board was appropriating hundreds of instream flow water
rights per year. These early instream flow recommendations relied heavily on the R2X Method and the
biological judgment or opinion of the biologist in the field because:
• Most of these flow recommendations were based on a single cross section or transect;
• The length of each segment varied depending on the availability of resources to collect data;
and/or
The measured discharge may or may not have been within, what we today consider, the
"accuracy range" of the model (2.5 or 0.4 times the measured discharge). •
Instream Flow Council
In 1998, a new organization was formed, comprised of members from state and provincial fishery and
wildlife agencies from the United States and Canada, called the Instream Flow Council (IFC). The IFC
was established as a nonprofit organization whose mission is to improve the effectiveness of instream
flow programs for conserving aquatic resources. In 2002 and 2004, the IFC published the original and
revised edition of "Instream Flows for Riverine Resource Stewardship ", a `bluebook' that could readily
be used as an industry standard for designing agency instream flow programs and studies for riverine
resource management (Annear, et al 2002). The IFC has identified and evaluated many of the different
Instream Flow Assessment Tools or Methodologies currently available, and recommends moving away
from the use of any one tool as a method to obtain a single "minimum" rate of flow and toward the use
of a suite of tools that provides variable flow regimes with intra- and inter-annual variability to maintain
and restore the natural form and function of stream channels, their fisheries and riverine resources.
Thus, a true minimum flow to maintain riverine processes is a quantity of water distributed over time in
varying amounts to maintain natural processes rather than a single, continuous rate of flow (Annear, et al
2004). The problem with this concept is: l) Current values and policies do not allow for protection of
flows above the determined "minimum flow" value without acquiring existing decreed water rights; 2)
How would you reasonably incorporate such a variable flow requirement into the state's water right
system; and 3) How would you administer such a water right? Because the majority of Colorado streams
still experience a peak flow occasionally, even with current development projections, the CDOW - •
believes the R2X Methodology can still be used alone or in conjunction with other flow assessment
methods to address the full range of hydrologic and hydraulic conditions required to preserve the natural
environment to a reasonable degree. However, the CWCB and CDOW should be cognizant of the
possible future need to protect different portions of the natural hydrograph to ensure the natural
environment is protected to a reasonable degree.