306 Twe;nty-se;venth Annual Report 



An earth reservoir, 60 feet inside diameter, has been built close to 

 the well, and the water can be discharged either into it or into an ele- 

 vated 3000-gallon tank, which is of suitable height for house service and 

 fire protection. The discharge from the reservoir is through a steel 

 slide gate and over a weir, and the stream used ordinarily will be about 

 400 gallons a minute. 



A new plant has been designed for the Salt River Valley Farm, also, 

 and the well has been completed. The original design was for a drilled 

 well, but the prices quoted, even for an 8-inch well, were so unreason- 

 able, and the log of the Tempe Canal Company's wells a mile away was 

 so favorable, that a well of the reinforced concrete caisson type was de- 

 cided on. Anticipating loose gravel, as in the canal company's wells, the 

 caisson was built heavy and strong, and is an excellent example of per- 

 manent construction. The well was sunk to a depth of 15 feet below the 

 water level and 40 feet below the ground surface. The log is as follows : 



Soil 2 feet 



Caliche 10 feet 



Sand and gravel 16 feet 



Cemented gravel 6 feet 



Sand and gravel 6 feet 



Cemented gravel 



Comparison of this log with those of the canal company wells and 

 wells to the southward shows that the Experiment Station Farm near 

 Mesa is situated on an old Pleistocene ridge or bajada while the others 

 are in Recent valley fill, at least to depth sufficient to give a good irri- 

 gation supply. The new well yields 110 gallons a minute, ample for 

 domestic purposes and gardens, but not for general field irrigation. The 

 use of groundwater for irrigation in the Salt River Valley should be 

 encouraged to permit of an extension of the irrigated area, and all in- 

 formation regarding the location of groundwater supplies is of value 

 and should be assembled. 



An experience of interest to pinnp irrigators was had at the Uni- 

 versity Farm at Tucson. The discharge from the horizontal centrifugal 

 pump dropped to 590 gallons a minute. It was observed that consid- 

 erable air was coming out with the water and the air was found to 

 be leaking in through the gland packing in spite of a water seal. On 

 resetting the packing and tightening the gland the discharge increased 

 to 650 gallons and by replacing the worn packing with fresh, the dis- 

 charge increased to 720 gallons, the normal amount, with no change in 

 the engine or pump speed. It is notable that the capacity of the pump 

 could be reduced 18 percent by a moderate air leak. At another time 

 the capacity was reduced about a fourth by a small stick which became 



