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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Figure 3- E indicates that this scenario would result in a water surface elevation approximately
6 feet higher for approximately 50 percent of the days during the study period as compared to the
baseline condition with no reallocated storage

6.2.2.4 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 20,600 acre-foot allocation
pool. The demand function used for South Metro was developed by South Metro's engineering
consultant on the basis of estimated releases, which, in turn, had been determined on the basis of
reservoir model studies. As a result, the reservoir simulation studies completed herein also
indicated that there was sufficient storage available to make releases to meet the demand
schedule almost every month. The simulation resulted in an average increase in lake elevation of
3.48 feet. During the summer months the average lake increase was 5.24 feet. Figures 4-A, 4-B,
4-C and 4-D show the detailed results of the simulation.

Figure 4-E indicates that this scenario would result in a water surface elevation approximately
3 feet higher for approximately 50 percent of the days during the study period as compared to the
baseline condition with no reallocated storage

6.2.2.5 Scenario 5: Central Water Conservancy District and Greenway
Foundation/Littleton. 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 55.1 percent of the time during the simulation and
resulted in an average increase in lake elevation of 4.69 feet. During the summer months the
average lake increase was 5.40 feet. Figures 5-A, 5-B, 5-C and 5-D show the detailed results of
the simulation.

Figure 5-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 7,700 Acre-Foot Pool

6.2.3.1 Scenario 1: Denver Water. Scenario I consisted of the use of junior water rights as
inflow to Chalfield Reservoir and the Denver drought contingency demand with a 7,700 acre-
foot allocation pool. The desired demand was met 84.9 percent of the time during the simulation
and resulting in an average increase in lake elevation of 3.80 feet. During the summer months
the average lake increase was 3.88 feet. Figures 6-A, 6-B, 6-C and 6-D show the detailed results
of the simulation.

Figure 6-E indicates that this scenario would result in a water surface elevation approximately
4 feet 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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