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

Reservoir) and one in the South Fork St. Vrain basin (Isabelle Lake). Despite their various
locations, it is recommended that these units be modeled together for the SPDSS effort due to
simplify modeling of operations of the Left Hand Ditch Company and due to the similar uses
associated with the storage units. The seasonal limitations on the use of the one small storage
unit not located in the Left Hand Creek basin (Lake Isabelle) is not anticipated to adversely
impact development of base flows in future modeling efforts.
Left Hand Valley Reservoir (Structure ID 0504488)
Left Hand Valley Reservoir is the largest of the ditch company storage units and was constructed
in 1945. Left Hand Valley Reservoir is located southwest of Table Mountain, as shown in Figure
1. Water is released from the reservoir through an outlet ditch that can deliver water directly to
Left Hand Creek or downstream ditches within the ditch company.
An elevation-capacity curve for the reservoir was provided by the Left Hand Ditch Company. A
subset of points from the curve is provided in Table 1.
Table 1
Left Hand Valley Reservoir
Stage -Area -Capacity Curve
Elev. Area Capacity
(ft) (Acres) (Ac-Ft)
0 - 17 NA 0
18 NA 100
20 NA 139
22 NA 183
24 NA 236
26
28
30 NA
NA
NA 299
371
456
Elev. Area Capacity
(ft) (Acres) (Ac-Ft)
32 NA 555
34 NA 670
36 NA 803
38 NA 953
40 NA 1122
42 NA 1310
44 NA 1516
45 113 1624
NA -not available
Source: Left Hand Ditch Compairy
Capacity:
Total Storage: 1,624 ac-ft
Active Storage: 1,624 ac-ft
Dead Storage: 0 ac-ft
113 maximum surface acres
Maximum outlet release of about 50 cfs as constrained by a culvert located downstream
Enlargement History: Left Hand Valley Reservoir has not been enlarged.
Reservoir Storage Measurement: Storage levels in Left Hand Valley Reservoir are measured
monthly by the Water Commissioner.
Seepage: Seepage from Left Hand Valley Reservoir is considered minimal.
Left Hand Ditch Operating Memorandum.doc 7 of 17 January 5, 2005