Mayarama

Capacity of Aquaducts

The capacity of an aqueduct is its maximum discharge, and 
this occurs when it is nearly but not quite full. For the case 
where the slope s is 0.0001894, the hydraulic radius r = 1.92 
feet, and c = 139 the mean velocity v is found by computa- 
tion to be 2.65 feet per second. Then the discharge q is 
127.2 cubic feet per second, or 82 200000 gallons per day; 
this capacity is sufficient for the supply of a city of 500 ooo 
people. If the slope of this aqueduct be 4 feet per mile its 
mean velocity and discharge will be double the above 
figures; a slope as great as this is, however, very uncommon, 
although greater slopes are said to have been used in the old 
Roman aqueducts. 

Domination Aquaducts

The famous Roman aqueducts were carried

across valleys on masonry arches in order to preserve a uniform 
slope; they were of rectangular cross-section, lined with con- 
crete, and covered with either stone slabs or arched roofs. 
Aqueducts are now built only for the supply of large cities, a 
pipe line being sufficient to carry it in ordinary cases; they 
are built below the surface of the ground and are carried 
through rock in tunnels. The word conduit is often used as 
synonymous with aqueduct, but it also applies to any large 
covered channel for carrying water. 

The cross-sections used for modern aqueducts are generally 
of the circular and the basket-handle form. The circular sec- 
tion is used for small aqueducts less than about six feet in 
diameter. 

Masonry Culverts

In all the masonry work of waste-weirs, gate chambers, and 
culverts hydraulic mortar of the best quality must be used 
and an efficient inspection be maintained to secure good 
material and workmanship. The strength of a structure is 
the strength of it weakest part, and hence if one part be 
defective through lack of proper inspection the security of the 
entire structure is correspondingly lowered. 

Aquaducts

The water pipes that run into a reservoir through an 
earthen dam should terminate in a gate chamber which is 
provided with valves for admitting and shutting off the flow. 
This gate chamber may be arranged so as to admit the water 
to it at different levels, for at certain seasons the water may 
be purer at one depth than at another. These openings are 
provided with screens to keep out fish. The gate chamber is 
necessarily of masonry, and it is hence generally built near 
one end of the dam where a good foundation may be obtained, 
and it often forms a part of the waste-weir structure. 

An arched culvert extended through the embankment is 
one of the best ways for bringing the pipes to the gate cham- 
ber, a thick stop wall being built at the upper end to keep 
the water out of it. The exterior of the arch stones should 
be left rough and puddled clay be rammed around them, so 
as to prevent all percolation of water. This culvert carries 
not only the water main, but also a smaller pipe which may be 
used to draw off the reservoir when repairing or cleaning is to 
be done.