14 BULLETIN 115, U. S. DEPARTMENT OF AGRICULTURE. 
and shows a great saving in material, for the reason that the amount 
of water entering the channel leading to the gate can be so easily 
controlled that there is little danger of failure from freshets, and 
no excessive amount of money was necessary to build expensive wings 
and a high bulkhead. 
In the following pages the diversion works of several systems, 
illustrating both the simple and more elaborate types of structures, 
are described. 
DIVERSION WORKS OF THE SOUTH SAN JOAQUIN AND OAKDALE IRRIGATION 
DISTRICTS. 
The combined structures shown in Plate IV furnish a general 
idea of arrangement for an efficient method of handling of water at 
the head of a canal. The joint headworks of the South San Joaquin 
and Oakdale irrigation districts are located in the canyon of the 
Stanislaus River about 18 miles above Oakdale, Cal. 
The river has a maximum flood flow, as shown by two floods within 
six years, of 62,000 second- feet. The low- water flow is about 100 
second- feet. Of the 1,500 second-feet which the structure is designed 
to take from the river but 1,370 feet will be delivered into the head 
of the canal below the lower gates, the surplus being wasted over the 
spillway or out through ' the sand and waste gate, back into the 
canyon below the diversion dam. 
The complete heading consists of the diversion dam of two arch 
spans with an intervening buttress, 466 feet in crest length, and a 
maximum height of 78 feet, and the joint headworks on the north 
end of the dam and of the separate Oakdale headworks on the south 
end. The following description is confined to the joint headworks: 
The joint headworks are built of concrete, part plain and part 
reinforced, installed upon and against solid rock foundations. 
There are four principal elements in the headworks: First, the 
head wall, with five openings designed to be closed with stop logs 
in case of accident to the gates below ; water covering the diversion 
dam more than 3 feet in depth tops this head wall. Second, a gravity 
dam placed on a tangent to the curve of the diversion dam, diverging 
about 16° from a right angle with the center line of the canal. There 
are three gate openings at right angles to the line of the canal, each 
6 by 9 feet, regulated by massive cast-iron gates raised by screw stems 
through geared hoists located on top of the gravity dam. The top 
of the gravity dam is 25 feet above the crest of the diversion dam 
and careful estimates show that maximum flood crests will top the 
diversion dam about 23 feet. Third, an automatic spillway about 
30 feet long just below the gravity dam at an elevation of 1^ feet 
below the crest of the diversion dam, and a sand and waste gate 
just downstream from the spillway. Fourth, three gates, each 6 feet 
