C150296 Feasibility Study

• Contract/PO #: CT2015-058
• Contract/PO #: C150296
• Contractor Name: Gypsum, Town of
• Contract Type: Loan
• Water District: 0
• County: Eagle
• Loan Projects - Doc Type: Feasibility Study

Gypsum Loan Feasibility Outline
CWCB Water Project Loan Program
Page 15 of 33
Watershed Information
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Watershed
LEDE USGS
Resenroir Ditch Beaver Cross
Drainage Area [ac] 660 1,173 9,472 21,888
Drainage Area [mi2] ~ 1.03 1.83 14.80 34.20
Maximum Elevation [ft] 10,4~3 12,018 13,173 14,00~
Minimum Elevation [ft] 9,498 10,083 7,4~3 7,992
Average Precipitatian [in] 25.1 30.6 ~7.0 30.6
Precipitation Volume [ac-ft] 1,378 2,995 ~1,~89 55,745
Diseharge Volume [ac-ft] - - 9,862 38,697
Discharge Ratio [°fo] - - 46 69
Bare Rock Ratio [°lo] 0 ~5 4 ~3
Est. Discharge Ratio [°lo] 20 70 - -
Est. Discharge Volume [ac-ft] 276 ~,097 - -
Notes
(A) The Gypsum Creek headwater catchment up-gradient of the LEDE Reservoir emhankment.
(B) The Antones Cabin Creek headwater catchment up-gradient of the LEDE Ditch headgate.
(C) The Beaver Creek watershed up-gradient of USGS Site 09067000.
(D) The Crvss Creek watershed up-gradient of USGS 5ite 09065100.
(1) The drainage area of each catchment or watershed in acres.
(2) The drainage area of each catchment or watershed in square miles; equals (1) divided hy 640.
(3) The highest elevation within each drainage area based on 1~3" NED.
(4) The lowest elevation within each drainage area based on 1C3" NED.
(~) The area weighted average annual precipitation falling within each drainage based on PRISM.
(6} The average annual precipitation volume falling within each drainage; same as {1) times (~ divided by 12.
(l) The average annual discharge volume measured by each USGS gage for the period corresponding tv (5).
~8) The percentage of (6j represented by [7); equals 100 times (T) divided by (6).
(9) The percentage of each drainage area covered by bare rock based on 1992 NLCD.
(10) The discharge ratio for each catchment estimated based on (9).
(11} The average annual discharge volume estimated for each catchment; equals (10] times ~) divided by 100.
In order to characterize the impact of land cover as a factor in the difference between the
two watersheds' discharge percentages, Raster Calculator was again employed to
characterize land cover within each drainage area based on 1992 NLCD land cover grid
data obtained from the USGS Nationa.l Map 5eamless Server, showing that bare rock
makes up about 4% of the land cover in the Beaver Creek drainage area and about 23% in
Cross Creek. The land cover data is depicted below with bare rock in grey. Since LEDE
Reservoir and Ditch catchments were found to consist of almost no bare rock in the
Reservoir's drainage area and about 25% bare rock in the Ditch's drainage area, it is
estimated that their average annual precipitation discharge percentages are about 20%
and 70% respectively. Applying these percentages to the incident precipitation volumes
already calculated, provides an approximate estimate of the average annual discharge
from each catchment, namely, 276 acre-feet (ac-ft) from the Reservoir's catchment and
2,097 ac-ft from the Ditch's catchment for a total hydrologic yield of about 2,373 ac-ft.