FLOOD10319

• County: Arapahoe
• County: Jefferson
• Stream Name: South Platte River
• Basin: South Platte
• Title: Chatfield Reallocation Study Storage Use Patterns
• Date: 2/1/2003
• Prepared For: CWCB
• Prepared By: Brown and Caldwell
• Floodplain - Doc Type: Project

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6.2.4 2,900 Acre-Foot Pool

6.2.4.1 Scenario 1: Denver Water. Scenario 1 consisted of the use of junior water rights as
inflow to Chatfield Reservoir and the Denver drought contingency demand with a 2,900 acre-
foot allocation pool. The desired demand was met 83.4 percent of the time during the simulation
and resulted in an average increase in lake elevation of 1.53 feet. During the summer months the
average lake increase was 1.57 feet. Figures II-A, 1l-B, 1l-C and 11-D show the detailed
results of the simulation.

Figure 11-E indicates that this scenario would result in a water surface elevation approximately
1 S feet higher for approximately 50 percent of the days during the study period as compared to
the baseline condition with no reallocated storage

6.2.4.2 Scenario 2: Central. Scenario 2 consisted of the use of junior water rights as inflow to
Chatfield Reservoir and the Central Colorado Water Conservancy District's augmentation
requirements with a 2,900 acre-foot allocation pool. The desired demand was met 32.3 percent
of the time during the simulation and resulted in an average increase in lake elevation of 0.40
feet. During the summer months the average lake increase was 0.73 feet. Figures 12-A, 12-B,
12-C and 12-D show the detailed results of the simulation.

Figure 12-E indicates that this scenario would result in only relatively minor increases in
Chatfield Reservoir water surface elevations over the study period.

6.2.4.3 Scenario 3: Greenway and Littleton. Scenario 3 consisted of the use of junior water
rights as inflow to Chatfield Reservoir and the release of stored water to meet minimum
streamflow requirements with a 2,900 acre-foot allocation pool. The desired demand was met
83.2 percent of the time during the simulation and resulted in an average increase in lake
elevation of 0.69 feet. During the summer months the average lake increase was 0.93 feet.
Figures 13-A, 13-B, 13-C and 13-D show the detailed results of the simulation.

Figure 13-E indicates that this scenario would result in only relatively minor increases in
Chatfield Reservoir water surface elevations over the study period.

6.2.4.4 Scenario 4: South Metro (M&I and Conjunctive Use). Scenario 4 consisted of the
use of junior water rights from the South Platte and Blue Rivers along with reusable effluent as
inflow to Chatfield Reservoir and the South Metro demand with a 2,900 acre-foot allocation
pool. Since the demand was previously modeled by South Metro's consultant as a function of
available storage, the true percentage that the demand was met is not available. The simulation
resulted in an average increase in lake elevation of 1.42 feet. During the summer months the
average lake increase was 1.16 feet. Figures 14- A, 14- B, 14-C and 14- D show the detailed
results of the simulation.

P:\Data\GEN\CWCB\Chatfie ld\Report 12.02\RevisedChatReport I 03\Report2-03 .doc

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