WSP03959

• File Number: 8443
• Description: Narrows Unit
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/8/1976
• Author: Wright Water Enginee
• Title: Questions related to Narrows Reservoir
• Water Supply Pro - Doc Type: Report/Study

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Que s t i on 1:

WILL CANAL LOSSES OF SUPPLEMEIHAL WATER DOWNSTREAM OF NARROWS AVERAGE 38%1

Answer 1:

No. They will average less.

A U.S. Bureau of Reclamation canal loss analysis made in 1965 indicates canal
losses of 28.5 percent.

A seepage run of the Point of Rocks (North Sterling) Reservoir Inlet Canal was
made in October, 1971, by Wright Water Engineers, Inc. which showed canal losses
of 26 percent for 51.8 miles of canal. This agreed with the U.S.B.R. figure of
25.5 percent for 1953. This amounts to about 0.5 percent per mile of canal.

Our seepage run study on Harmony No.2 Ditch showed a 10 percent loss for a
canal length of 8. I miles. This amounts to a loss of about 1.2 percent per
mi Ie.

The average U.S.B.R. computed overall seepage losses are 28.5 percent. Sup-
plemental water losses would be less than average canal losses because supple-
mental water would be carried "piggyback" in the canals, and at a time of the
year when the canals had already been wetted by earlier diversions of river
water.

The sediment regime of the South Platte River will be altered as silt in the
river settles out in the Narrows Reservoir. Clean water will be diverted by
upstream ditches which may increase canal losses. In our opinion, even with
increased losses, supplemental water losses will average less than 28.5 per-
cent. More detailed study could refine these numbers better.

References:

I. U.S.B.R. Historic Basis Analysis - February 25, 1965.

2. Letter Report, Lower South Platte Water Conservancy District - Re:
Seepage Run, Wright Water Engineers, Inc., October II, 1971.

3. Letter Report, Harmony No.2 Ditch, Water District #64, Division I,
Description of Ditch and Operation, Wright Water Engineers, Inc.,
September 14, 1968.

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