17 ‎(3)‎

• Board Meeting Date: 1/23/2008
• Description: ISF Section - Injury with Mitigation - Case No. 3-99CW34; application of Charles E. Nearburg
• Board Meetings - Doc Type: Memo

Colorado Water Conservation Board
J alluary 7, 2008
Page 4

No diversions will be made when flows at the gage are less than or equal to 15 cfs.

Under the foregoing schedule, the flow-through diversions into the ChalUlels, for recreation)
piscatorial, alld fish and wildlife habitat purposes, will never exceed 3.8% of the flow in Trout
Creek. In addition, no diversions will occur when flows are less than 15 c.f.s., a rate at which
two out of the three CWCB hydraulic criteria for instrealll flows are exceeded, as fin1her
described in subparagraph ILB, below.

In addition to the foregoing direct flow diversions from Trout Creek, the ChalUlels will be
excavated st11lctmes and may also intercept ground water 1ributal'y to Trout Creek. Such ground
water will provide a neceSSal.y source of water for fish habitat during the winter (October 16 to
April 30). Depletions associated with evaporation alId secondary evapotranspiration from the
'Challl1els are estimated to total between 2.6 alld 4.1 acre-feet alU1Ually. Under the injury with
mitigation plan, such depletions will be deemed to occur as the result of surface water diversions
from Trout Creek, given the sU1mneIiime diversions of surface water from the Creek and the
negligible lag in groundwater depletions to the Creek in the winter.

B. Benefits of mitigation. The benefits to the natural environment from Mr.
Neal.burg's stream restoration alId habitat improvement projects on Trout Creek are detailed in
the May 2007 repoIi from Black Creek Hydrology, and Feb11lal'y 2000 reports from Wright
Water Engineers (both previously provided to CWCB staff), alld will be more fully described at
the presentation during the BOal'd's Janual.y 22/23,2008 meeting. As stated in the Black Creek
Hydrology rep0l1, Mr. Neal'burg's work on Trout Creek has had a "remarkable effect on the local
strealll system," trallsforming the "severely degraded, eroded and braided conditions on
[approximately 1.5 miles of] Trout Creek') into a "single thread challl1el alId deep pool habitat"
that now provides an "excellent fishery," holds all abU1ldance of fish and provides cool summer
water and deep pool habitat for winter.

In 1999 alId 2000, Wright Water Engineers conducted a bioassessment of Trout Creek,
including a hydraulic allalysis to evaluate the tiuee principal criteria (average depth, average
velocity, alId percent wetted perimeter) used by the CWCB to develop biologic instrealll flow
recommendations. Excerpts of this analysis are enclosed (alld tile complete repoIis were
previously provided to the CWCB staff). This allalysis measured and modeled flows in Trout
Creek at three different stations (see enclosed map), and used methods similal. to the CWCB's
R2CROSS methodology. The upper-most location (Station I) was chosen because it is located
on an un-restored portion of Trout Creek, while the lower stations al'e located in the improved
sections of tile stream on Mr. Nearbmg's propeliy.

Wright Water concluded that, at Station 1 (tile un-restored stTeam location), only one of
the CWCB hydraulic criteria was satisfied at flow rates of both 35 c.f.s. (the decreed
summel1ime instrealll flow rate) and 15 c.f.s. At the lower stations, however, all tlu.ee criteria
were satisfied at a flow rate of25 c.f.s., and two out of three criteria were satisfied at a flow rate
of 15 c.f.s. These findings are significant because, under the current injury with mitigation
proposal, diversions of 1 c.f.s. into the ChalUle1s will occur only when the gaged flow in Trout