FLOODC00270

• County: Jefferson
• County: Arapahoe
• Title: Chatfield Reallocation Study: Storage Use Patterns 2/1/2003
• Date: 2/1/2003
• Prepared For: Jefferson County / Arapahoe County
• Prepared By: US Army Corps of Engineers/CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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6.2.3.2 Scenario 2: Central. Scenario 2 consisted ofthe use of junior water rights as inflow to
Chatfield Reservoir and the Central Colorado Water Conservancy District's augmentation
requirements with a 7,700 acre- foot allocation pool. The desired demand was met 50.2 percent
of the time during the simulation and resulting in an average increase in lake elevation of
1.63 feet. During the summer months the average lake increase was 2.07 feet. Figures 7-A, 7-B,
7-C and 7-D show the detailed results of the simulation.

Figure 7 - E indicates that this scenario would result in a water surface elevation approximately
I foot higher for approximately 50 percent of the days during the study period as compared to
the baseline condition with no reallocated storage

6.2.3.3 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 7,700 acre-foot allocation pool. The desired demand was met
85.9 percent of the time during the simulation and resulting in an average increase in lake
elevation of 2.08 feet. During the summer months the average lake increase was 2.43 feet.
Figures 8-A, 8-B, 8-C and 8-D show the detailed results of the simulation.

Figure 8- E indicates that this scenario would result in a water surface elevation approximately
I foot higher for approximately 50 percent of the days during the study period as compared to
the baseline condition with no reallocated storage

6.2.3.4 Scenario 4: South Metro (1\1&1 and Conjunctive Use). Scenario 4 consisted ofthe
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 7,700 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 2.36 feet. During the summer months the
average lake increase was 2.84 feet. Figures 9-A, 9-B, 9-C and 9-D show the detailed results of
the simulation.

Figure 9- E indicates that this scenario would result in a water surface elevation approximately
2 feet higher for approximately 50 percent of the days during the study period as compared to the
baseline condition with no reallocated storage

6.2.3.5 Scenario 5: Central and GreenwayILittleton. Scenario 5 consisted of the use of
junior water rights as inflow to Chatfield Reservoir and maximum demand from either Scenario
2 and 3 since water used to meet minimum streamflows in the Denver area could then be utilized
for augmentation purposes for Central. The desired demand was met 40.5 percent of the time
during the simulation and resulted in an average increase in lake elevation of 1.34 feet. During
the summer months the average lake increase was 1.80 feet. Figures 10-A, 10-B, 10-C and 10-D
show the detailed results of the simulation.

Figure 1 0- E indicates that this scenario would result in a water surface elevation approximately
I foot higher for approximately 50 percent of the days during the study period as compared to
the baseline condition with no reallocated storage

P: \Data\GEN\CWCB\Chatfield\Report12.02\RevisedChatReport 1 03\Report2-03 .doc

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