The Arizona sentinel., 1908-08-12
Irrigation of
 Yuma Valley
TContinued from Page One.

y '
 extensive coffer dam as we'll as
 other temporary barriers to drain
 the river bed, so that a founda-
 tion could be laid. Work was
 also begun upon the levee pro-
 tectiOnS referred to, until the construction has reached such a
 point that it has been thoroughly tested by exposure to flood cur
 rents, with the result that no damage of importance has been done to either the concrete struc
 ture or the protecting banks.
 The extensive mileage of lev ees is partly necessary protect the main irrigating canals, of which there will be one on each side of the Colorado. The canal on the Arizona side will be 16 miles iu/length, the one on the California side 10 miles in length, making total of 26 miles and serving 13S miles of laterals, by which the water will be distrib- uted over the bottoms. The water will enter the canals through gates, while pumping machinery will be installed at several points where Fit will be necessary to raise the water sup ply to a higher level to serve the laterals. It is calculated that the dam, which is the only one of it's kind in this country, will be of sufficient capacity to fill the main storage reservoir, which will have an area of 10 square miles. The dam is known as an India weir dam, being of a de- sign which has been very suc- cessfully employed in East In dian irrigation, where it is usual ly constructed of wood.
 In building the dikes or levees much of the labor is done by scrapers and blows drawn by horses, as the soil being stone less and soft can easily be heap ed up and graded to the proper level. The work. of building these levees is quite similar to the artificial embankments form ed to restrain rivers in the south, the width at the bottom usually being several times the width at the top, although the crest of the embankments is ample to permit the building of railway tracks here and there, thus using it as a roadway. As the quantity of concrete required would be so great that it would be far too expensive to use in protecting the levees, and deposits of natu- ral stone are too far distant to be employed, the main defense of the levees against the food currents, as already stated, is woodwork in some form. This is obtained from timber tracts in the vicinity. Young trees are used extensively, the trunks be- ing cut into suitable lengths and used for the foundation of the mating or ahatis. This founda- tion is fastened securely together and upon it laid smaller limbs, their ends pointing up and down stream, like the fascines of an cient Notifications. Bunches of brushwood and shrubbery form the next layer, being worked in among the boughs beneath. In another form of wooden frame work posts are driven into the earth deep enough to secure firm foundation, in which they hold rigidly. Then a sort of fence is made by mailing limbs of trees from post to post. The face of this fence is further pro- tected by driving piles into the earth in front of it's upstream face. Both in the front and rear of the fence are arranged layers of boughs and brushwood, some times covered over with earth and sometimes left bare.
 These dikes are intended not only to protect the entertainments, but to be land makers. Each outward from the levee a certain distance into the river channel, but at such an angle that 1t will catch driftwood and other fiotsam which may come