Lower South Platte River Study

• Contractor Name: Colorado Water Conservation Board
• Loan Projects - Doc Type: Feasibility Study

ILower South Platte River Study
Colorado Water Conservation Board
IDecember 2001
I Water placed into storage could be released directly to the South Platte River with an outlet
ditch from the reservoir. Alternatively, existing ditches, such as the Highline Ditch which is
the outlet ditch from Julesburg Reservoir, could be used to convey stored water to Lodgepole
ICreek. Again, winter operations could be very difficult because the Harmony Ditch and
Highline Ditch are shallow and have many structures.
IThe Peterson Ditch has the greatest potential for winter operations because the distance from
the river headgate to potential storage sites is relatively short. Still, winter season operations
Iwould be very difficult.
Storage also could be filled by pumping from the river or large-capacity alluvial wells. This
Ifilling method would overcome canal capacity and winter operating constraints of a gravity
system; however, pumping would add significantly to the cost of storage development.
IWater available for diversion at the North Sterling, Harmony, and Peterson headgates was
estimated from the studies by NCWCD. Available water by month for the 1943-97 period
I provides the basis for the operations/storage/yield model, as described in Appendix A. Water
available for diversion from the river under a junior water right was adjusted to create a set of
feasible monthly diversions. The feasible diversions, shown in Tables 2-4 through 2-6, are
Ithe lesser of the following:
• The physically and legally available water as indicated by the NCWCD analyses
• The available capacity of the canal or ditch as determined from historical flow
records for the same study period(1943-97)
ICharacteristics of the canal and ditch systems relevant to the analysis are presented below:
I North Sterling Canal
Characteristic(1) Inlet Outlet Harmony Peterson
I Maximum Capacity, cfs 600 200 450 93
Winter Capacity, cfs(2) 240 80 180 36
Loss, % per mile per month 0.5 0.5 0.5 0.5
ICarriage
(1)Based on information from the respective irrigation companies.
(2)Based on 40%historical winter capacity utilization factor for the North Sterling Inlet Canal.
IThe carriage loss of 0.5 percent per mile is based on reported losses in the North Sterling
system (25 to 30 percent in the inlet canal and 15 to 30 percent in the outlet canal, including
Ievaporation from North Sterling Reservoir). These losses (25 percent for the inlet and 15
percent for the outlet) converted to a loss per mile of canal of 0.5 percent. This loss figure
was applied to the other canals to estimate losses outside of their normal use periods.
GEI Consultants, Inc. 2-10 01002 Dec 2001 Lower South Platte River Study