Section4_Rec-EnvWithFigs

• Title: SWSI Phase 2 Report - Section 4 Delineating and Prioritizing Colorado's Environmental and Recreational Resources and Needs
• Date: 11/7/2007
• Author: CWCB
• SWSI II - Doc Type: Final Report

Section 4
Delineating and Prioritizing Colorado's Environmental and Recreational Resources and Needs
creating the third coverage was more complex and is
discussed below.
Role of Water Availability in Appropriation
Members of the Environment and Recreation TRT
thought it might be useful to identify stream
segments that have decreed instream water rights
where water availability may have played a role in
the quantity of water that was appropriated To gain
insight on this, the database was searched to
identify stream reaches that had the following data
qualifiers:
1. ISF appropriations that have three or more flow
periods.
2. ISF appropriations that have a downstream
terminus at a headgate.
Stream Reaches with Multiple Flow Periods
For all ISF appropriations, CWCB is required to
determine:
~ That there is a natural environment to preserve
~ That water is physically available for the Board to
appropriate.
~ That the natural environment can exist without
material injury to existing water rights.
Typically, most ISF recommendations consist of two
parts a winter and summer flow. When
determining water availability, staff occasionally
find periods of the year where the recommended
flows are not present. In these cases, staff will often
recommend an additional, reduced flow period to
better reflect the natural hydrologic conditions of
the stream. For instance:
Happy Creek ~ ~ • -
6.00 Apr 1 to Jun 14
4.00 Jun 15 to Oct 31
2.25 Nov 1 to Mar 31
Source: CWCB http://cwcb.state.co.us/
with three or more flow periods will help to identify
the streams where water availability was limited
during some periods of the year. These streams could
then be candidates for additional strategies such as
the acquisition or donation of senior water rights for
ISF purposes. It should be noted that the
modification of flow recommendations may not be
due to water diversions, but may result from natural
stream conditions. Consequently, the information
from the database should be viewed as an initial
screening tool. If the subject reach is deemed to be of
interest, additional data gathering would be
recommended to obtain more information regarding
water availability.
Instream Flow Appropriations That Have a
Downstream Terminus at a Headgate
ISF appropriations that have a downstream
terminus at a headgate also relate to CW CB's water
availability determinations. During the ISF process
investigation, CWCB may determine that a
particular diversion structure diverts a portion of
the streamwhere an ISF appropriation is proposed.
In this case, CWCB may recommend that the
downstream terminus of the proposed ISF water
right end at the headgate. These streams could also
be candidates for additional strategies such as the
acquisition or donation of senior water rights for ISF
purposes. It should be noted that there may be
additional factors or reasons why a diversion
structure was chosen as the downstream termini
other than water availability.
Role of Water Availability in Appropriation
Coverage Generation
The Stream and Lake Protection Database was
searched to determine streams that have three or
more flow periods and/or those that contain the
following terms in the lower terminus description:
headgate, headgate diversion, and ditch. The entire
database can be viewed at http://cwcb.state.co.us/
streamandlake/tools.htm.
In this example, the summer flow recommendation Three searches of the database were performed to
of 6 cubic feet per second (cfs) from April 1 to produce the requested information. The first was
October 31 reduced to 4 cfs from June 15 to October limited to streams where headgate, headgate
31 based on water availability. ISF appropriations diversion, or ditch was contained in the lower
terminus description. The next two searches worked
n~ FINAL DRAFT 4-7