162 Bulletin 86 



Drain tile is made with square ends, without bell or socket, and 

 is laid end to end with open joints to admit water. Cement pipe 

 cannot be recommended for drain tile except with some qualifica- 

 tion. A chemical analysis of the groundwater to be drained should 

 first be made. As noted on page 141, the action of alkali on con- 

 crete depends on the character of the alkali, the degree of concen- 

 tration, and the density of the concrete. The evidence at hand in- 

 dictates that wet-poured or machine-made cement pipe, made of 

 carefully selected materials so as to have great density, would prove 

 satisfactory in Arizona. More evidence as to the life of cement 

 pipe in drainage ditches is very desirable. When the Tempe drain- 

 age canal was first opened the water at the outlet contained 1665 

 parts per 100,000 of soluble solids, but after one year the soluble 

 solids had decreased to 351 parts per 100,000. 



The Thatcher drainage district is using clay tile. The cost is 

 about 50 percent greater than for machine-made cement pipe. 



GATES 



The cheapest material for directing water in and out of laterals 

 and open head ditches and for taking the water from the head 

 ditches onto the lands is the earth always close at hand, but the 

 time consumed in building and removing the earth taps makes its 

 use very arduous and costly. Lumber gates are, therefore, em- 

 ployed sometimes, but the alternate wetting and drying soon de- 

 strovs them. Cement pipe in 2-foot lengths with sheet-iron curtains 

 are to be recommended for this purpose. A good type of cement 

 pipe gate is shown in Fig. 37. If the ditch banks are high and 

 wide, an additional 2-foot length of pipe should be used so as to 

 reach entirely through the bank. 



UNDERFLOW COLLECTING FLUMES AND INVERTED 



SIPHONS 



Many of the dry water courses of the Southwest carry a strong 

 underflow, and after the flood seasons are past much water is ob- 

 tained by opening ditches or burying wooden flumes as deeply as 

 possible in the river beds. But the recurrent floods fill the ditches 

 and oftentimes float away the buried boxes so that the expense 

 of maintenance and the loss of water at critical times is very dis- 

 couraging. 



