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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Table ES-1. Frequency Entity Met its Target Release for 1946-1990
Scenario 20,600 AF Pool 7,700 AF Pool

2,900 AF Pool

1. Denver

88.6%
78.0%
90.8%
99.3%

83.4%
32.3%
83.2%

84.9%
50.2%
85.9%

2. Central

3. Greenway and Littleton

4. South Metro'
5. Mixed Use: Central and
Greenway/Littleton 55.1% 40.5% 26.5%
'Frequency of meeting target release is very high because the targets provided by South Metro were based on
modeled storage results which indicated these targets could be met 100 percent of the time.

99.5%

99.7%

Tables ES-2 and ES-3 below compare: (I) the average daily increase in Chatfield Reservoir
water surface elevation (in feet) that resulted from the reallocated storage space with (2) the
present situation in which there is no reallocated storage space.

Table ES-2. Average Daily Increase in Chatfield Reservoir Water Surface Elevation
With Storage Reallocation for 1946-1990 (feet)
Greenway and
Littleton
6.22
2.08
0.69

Pool Size (AF) Denver Water
0,600 8.97
',700 3.80
>,900 1.53

Central
6.28
1.63
0.40

South Metro
3.48
2.36
1.42

Central and
Greenway/Littleton
4.69
1.34
0.34

Table ES-3. Average Daily Increase in Chatfield Reservoir Water Surface Elevation With
Storage Reallocation for Memorial Day to Labor Day for 1946.1990 (feet)

Greenway and Central and
Pool Size (AF) Denver Water Central Littleton South Metro Greenway/Littleton
20,600 9.38 6.84 6.90 5.24 5.40
7,700 3.88 2.07 2.43 2.84 1.80
2,900 1.57 0.73 0.93 1.16 0.68

In conclusion, results from this investigation indicate that there is additional storage space
available in Chatfield Reservoir, and that there are sufficient water rights and demand to utilize
this additional storage. Based on the data, analysis and findings from this investigation, the
following detailed conclusions and recommendations are presented:

I. Available water rights to those entities expressing interest in acquiring and
utilizing reallocated storage space in Chatfield Reservoir are sufficient to allow
these entities to make efficient use of at least 20,600 acre-feet ofreallocated
Chatfield Reservoir storage.

2. If the new HEC-5 runs by the Omaha District, U.S. Army Corps of Engineers for
investigating Chatfield Reservoir, Bear Creek Reservoir and Cherry Creek
Reservoir system operations indicate potential for reallocating more than 20,600
acre-feet of storage in Chatfield Reservoir, the analysis described in this report for
determining the effects of reallocating Chatfield Reservoir storage could be
repeated for a larger reallocated storage pool.

P:\Data\GEN\CWCB\Chatfield\Report12.02\RevisedChatReportl 03\Report2.03 .doc

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