WSP11249

• File Number: 8143.800
• Description: John Martin Reservoir - Water Sales and Contracts
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 12/1/1997
• Title: Report of the Colorado State Engineer - Concerning Accounting of the Operations of an Offset Account in John Martin Reservoir for Colorado Pumping - 1997 -- Part 2 of 2
• Water Supply Pro - Doc Type: Report/Study

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Mr. Steven J. Witte
July 9, 1997
Page 2

.......1-
Q

The diversion, measured at the 5-foot Parshall flume, was about 11.3 cfs at 5:35
a.m. and about 8.7 cfs at 6:00 p.m. With these small diversion rates, it was not possible
to measure the wasteway deliveries through the whole range of expected conditions. We
did, however, measure the wasteway discharge for four gate openings with discharges
ranging from 3.46 cfs to 7.49 cfs. The water drops about 20 feet from the gate down a
shale bank to a channel leading to the Purgatoire River. The discharge was measured in
the channel at a point about 15 to 20 feet upstream of the confluence with the river.
Attached are copies of the discharge measurement notes.

Following is a summary of the data and calculations:

Measured Gate Staff
Discharge, Setting, Gate aDenina Gage Ht H
cfs inches inches sa. ft. ft ft C
3.46 56-7/8 7/8 0.2507 0.55 3,50 0,919
4.98 56 1-3/4 0.5013 0.415 3.365 0,675
6.88 55-1/4 2-1/2 0.7161 0.20 3.15 0.675
7.49 54-1/2 3-1/4 0,9310 0.065 3.015 0.577

The discharge coefficient, C, is calculated by rearranging the equation described earlier.

The gate leaks on both edges of the gate frame, and with the smaller gate opening,
7/8-inch, it was visually apparent that the leakage was a significant portion of the total
flow. Accordingly, we will not use that measurement in determining a discharge
coefficient for the orifice equation. The three discharge calibration coefficients for the
other measurements average 0.642. Substituting the known values into the orifice
equation yields:

Q = 0.642A~2gH or

Q = 0.642 (8.025) (41.25 x DJ ./2.95 + S or
144
Q = 1.476D ./2.95+S where
Q = discharge, cfs
D = gate opening, inches
S = staff gage height, feet

The above equation was used to generate the enclosed rating table. We realize that the
relationship should be checked with respect to larger discharges. Bill Howland will' inform
us as to the likelihood of larger divertible flows based on the flow at the Thatcher and
Ninemile gages so that we can make additional measurements this'summer.

At low diversion rates, the Highland Canal Company often rotates the water to the
various turnouts. There may be times that all of the water will be delivered to LAWMA