SPDSS_Task5_KeyStructure_LeftHandDitch

• Title: SPDSS Task 5 - Key Structure, Left Hand Ditch System
• Description: The Left Hand Ditch System has been identified as a key structure for the South Platte Decision Support System ‎(SPDSS)‎ consumptive use and surface water modeling efforts. The purpose of this Task 5 memorandum is to document physical, legal, and operational aspects of those key structures identified.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/5/2005
• DSS Category: Surface Water
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153954
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Leonard Rice Engineering

Allens Lake (Structure ID 0504077)
Allens Lake is an off-channel reservoir located west of Table Mountain under the Lake Ditch,
which diverts near the bottom of Left Hand canyon. The lake was enlarged from the site of a
natural lake in the early-1900s. The ditch company did not come into possession of the lake until
about 1920. An outlet pipe from the lake provides share water to North Tollgate Ditch and South
Tollgate Ditch, which go around the north side and south side, respectively, of Table Mountain.
An elevation-capacity curve for the lake was provided by the Left Hand Ditch Company. A
subset of points from the curve is provided in Table 2.
Table 2
Allens Lake
Stage -Area -Capacity Curve
Elev. Area Capacity
(ft) (Acres) (Ac-Ft)
0 NA 0
2 NA 5.61
4 NA 114.09
6 NA 176.27
8 NA 241.75
10 NA 310.51
Elev. Area Capacity
(ft) (Acres) (Ac-Ft)
12 NA 382.57
14 NA 547.91
16 NA 536.55
18 NA 618.47
20 3 5 703.83
NA -not available
Source: Left Hand Ditch Compairy
Capacity:
Total Storage: 704 ac-ft 35 maximum surface acres
Active Storage: close to 704 ac-ft
Dead Storage: Small amount; exact capacity unknown
Maximum outlet release through a 24-inch outlet pipe (flow limit unknown)
Enlargement History: Allens Lake was enlarged (approximately 570 ac-ft) in 1908.
Reservoir Storage Measurement: Storage levels in Allens Lake are measured at the end of the
summer and at the end of the storage season.
Seepage: Seepage from Allens Lake is considered minimal.
Left Hand Park Reservoir (Structure ID 0504076)
Left Hand Park Reservoir is an on-channel reservoir located at about 10,500 feet elevation at the
very top of Left Hand Creek. The earthen dam holding back the reservoir breached on a number
of occasions in the late-1800s/early-1900s causing property damage and at least one fatality. The
reservoir site lay idle for a long time and the dam was rebuilt and enlarged in about 1966. A
Left Hand Ditch Operating Memorandum.doc 8 of 17 January 5, 2005