Lower South Platte River Study

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

Lower South Platte River Study
Colorado Water Conservation Board
IDecember 2001
The feasible monthly diversions were used as input to a spreadsheet model that simulates
Ireservoir operations with consideration (on a monthly basis) of:
• Reservoir evaporation at 4.16 inches/month.
I • Reservoir seepage at 0.2 percent of the storage contents per month.
I • Specific target releases, following a monthly delivery schedule during the irrigation
season(April through October). In each year of the 55-year record, there are seven
I months (April through October) during which water is released (i.e., 385 months).
The target releases can be viewed as a developed water supply with given levels of
reliability.
I
Evaporation and seepage allowances given above are based on experience and judgment of
Ithe consulting team.
The spreadsheet model (Appendix A) was used to examine two cases for each canal system:
I • No diversions during the winter months (December and January) in order to avoid
problems with operations and maintenance due to ice, i.e., no winter diversion.
I
• A case in which winter diversions are assumed to be possible.
IResults of the spreadsheet operations analyses are summarized below:
I Target With Winter Diversions No Winter Diversions
Target Target
Supply System Storage Release Reliability Storage Release Reliability
I (af) (af) `afl (at)
North Sterling Canal 15,000 5,000 86% 15,000 5,000 80%
10,000 3,300 89% 10,000 3,300 83%
I Harmony Ditch 15,000 5,000 95% 15,000 5,000 90%
10,000 3,300 95% 10,000 3,300 91%
I Peterson Ditch 15,000
10,000 5,000 96% 15,000 5,000 89%
3,300 98% 10,000 3,300 94%
I Reliability is measured by the number of months in the period of record during which the
target release of water can be met with the amount of storage provided. Results indicate that
the ability to operate in winter would materially improve the reliability of the water supply
Ideveloped with the new storage reservoir.
I
IGEI Consultants, Inc. 2-14 01002 Dec 2001 Lower South Platte River Study