18 BULLETIN 115, U. S. DEPARTMENT OF AGRICULTURE. 
will carry water 3 feet deep on a grade of 4.2 feet per mile. The 
gate structure has two openings regulated by steel gates, with a rack- 
and-pinion lift. The crest of the wings and the curtain wall above 
the openings are such that the maximum flood known to the stream 
can pass over the dam without topping the structure. The ditch be- 
low the gate is separated from the creek by a stepped concrete wall. 
"When the writer saw this structure in May. 1912. there was about 
1 foot of water passing over the weir, developing sufficient pressure 
on the openings to induce a velocity of 7 or 8 feet (estimated) per 
second in the upper reaches of the canal. As only a small amount of 
water was needed in the canal the gates were opened but a few inches. 
The high velocity caused scouring of the canal sides for about 100 
feet below the gate. This condition suggested that the water might 
be delivered to the canal much more gently by casting some flash- 
board grooves in the sides of the gate structure downstream from 
the openings so that boards might be inserted in these grooves and 
the elevation of the water below the gate kept at such a height that 
the shutters could be opened wide and the velocity of the entering 
water correspondingly reduced. The water would fall over the 
flashboards in a vertical drop and the velocity of the water below the 
structure cause no damage. If the full capacity of the canal should 
be desired, the flashboards would be pulled and the elevation of the 
water in the canal would prevent high velocity at the upper end. 
At the time the photograph shown in Plate V. figure 1. was taken 
all of the water not entering the canal was passed through the sluice- 
way in the diversion dam. This not only serves to carry most of the 
sand down the stream, but also makes it possible to draw off the water 
below the crest of the dam in order to make repairs. 
HEAD GATE, UINTA COUNTY IRRIGATION CO., WYOMING. 
A good example of modern construction of a river gate for a canal 
diverting water from a secondary channel of the stream is furnished 
at the head of the Cottonwood Canal in Uinta Countv. Wyo. (PL 
V, fig. 2.) 
Ball Island separates the stream into two branches and the gate is 
installed on one of these. The amount of water flowing in the 
branch supplying this gate can be regulated roughly by logs and 
brush in the channel at the head of the island. This regulation pre- 
vents the heavy flood flow of the stream from coming with full force 
against the gate structure and the saving in construction, due to this 
safe position, is evident from the view shown. It will be noted that 
the wing walls do not rise far above the natural surface of the bottom 
land. 
This gate supplies a canal 20 feet wide on the bottom with water 
3 feet deep, The carrying capacity is 140 second-feet. The gate is 
