WSP08097

• File Number: 8507
• Description: Rio Grande Project
• State: CO
• Basin: Rio Grande
• Date: 2/1/1961
• Title: Final Report Hydralic Model Studies
• Water Supply Pro - Doc Type: Report/Study

knowledge of flow depths in the river at different discharges, the sill

elevation for the structure can be determined.

Sill Height and Shape - It is desirable that the water depth over

the crest of the structure be greater than critical depth so that flow

measurements can be made on the crest of the structure. The height of sill

at the downstream end of the weir relative to the crest, should therefore

be sufficient to maintain control through the desired range of discharges,

yet not be too high so that velocities at the lower flows would be too small

for measurement by current meter. A sill height of one foot was found to be

adequate to maintain control and was used throughout the studies of Weir G.

Consideration was given to the possibility of sloping the sill and

crest of the structure laterally across the channel to provide a low point

for flow measurement at low discharges. Unless the angle of the V so-

formed is fairly small, considerable variation in the water surface over

the sill could result at low discharges. Visualize a lateral slope in the

sill of 6 inches in 200 feet. (0.0025). Similar difficulties would result

at high discharges because of cross flow and resulting non-uniformity of flow

over the weir.

Sand Bars - The results of studies in the 2-ft flume showed that

aggradation of the upstream bed to the crest of the weir does not affect the

stage-discharge curve. Therefore, sand bars at or below this level will not

affect the flow distribution or lateral water surface profile over the weir.

The studies were concentrated on sand bars that extended above the

crest of the weir. Various widths and locations of the bars relative to

the structure were investigated. To facilitate the laboratory procedure,

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