54 BULLETIN L15, U. S. DEPABTMBNT OF A.GRICULTURE, 
It amounts to a lined section of canal with a shallow cut-off wall at 
each end and a delivery tube through the bank, regulated by a sheet- 
iron gate. Debris is kept out of the delivery by a screen extending 
across the recess in which the gate is set. For most systems this 
screening would not be necessary. If the water in a lateral using 
this type of structure is to be checked up more than 2 feet above the 
bottom it would be well to extend the lined section farther down the 
channel and carry the lower cut-off deeper into the bed of the ditch. 
This depth will be determined in all cases by the material of the bed. 
In adopting this plan a cheaper installation is made by omitting 
the recess for the gate shutter, allowing both banks of the lined sec- 
tion to slope uniformly to the bottom of the ditch. The gate shutter 
can be sot on this slope, using the connections and gates as made by 
the manufacturers for a connection with a tube at 45° or (30° with the 
gate standards. 
SAND GATES. 
Some designers attempt to exclude the sand before it enters the 
canal by installing a sluice gate with a sill below the intake of the 
canal, adjoining the river gates on the downstream side, but as a rule 
the water is so agitated at the heading that only the heavier sand 
remains on the bottom and the lighter particles, whirling about in 
the water, are passed on through the gate to settle in the canal at 
some point lower down where the velocity is reduced to such an 
extent that the sand is no longer rolled along the bottom. 
It is probably much better to install a separate sand structure far 
enough below the head of the canal so that the latter will have gained 
enough elevation over the bed of the stream to obtain a good flushing 
velocity, and scour out the sand deposit from time to time as water 
is available. If the water rights on the stream are such that there are 
other consumers on the stream below the sand gate entitled to water 
at all times, then an arrangement may be effected so that a surplus 
amount of water can be run and the sand gates left open throughout 
the season, returning the surplus water to the stream. Kansas recog- 
nizes this benefit by legislation in its favor. 
THE SUMP GATE. 
There are three general types of gates to remove the sand belo&v the 
headgate of a canal system. The first consists of a sump connected to 
a discharge ditch or natural channel by gates located below the 
normal grade of the canal. This construction makes a combination 
sand and waste gate. Such a gate as this may be partly opened all 
the time or it may be closed completely except when a flushing head 
is available and then opened wide and all the water in the canal used 
for a short period to wash out the sand which has accumulated. The 
