Arizona Agricui^tural Experiment Station 305 



to, but necessary in the Antelope Valley and in some other localities in 

 Arizona that are exposed to occasional heavy floods. 



TRANSPIRATION STUDIES 



In order to study the relationship between duty of water and 

 transpiration, evaporation, and altitude, three sites have been chosen, 

 one each near Yuma, jNlesa, and Willcox. Special studies will be made 

 to test the hypothesis that the duty of water is measurable by the evapo- 

 ration rate. In cooperation with the U. S. Weather Bureau, an evapora- 

 tion station, equipped with an anemometer, a rain gauge, thermometers, 

 and a pan of the new standard lesign, has been established at each 

 station. 



Special studies have been made, also, of transpiration from trees in 

 the San Pedro \^alley. 



STATION PUMPING PLANTS 



A new pmuping plant was installed at the Sulphur Spring Valley 

 Dry Farm during the past year. It was desired to obtain a flow of 100 

 gallons of water a minute for supplementary irrigation. The well is an 

 8-inch hole, 130 feet deep, bored with an auger and cased with light 

 weight galvanized perforated metal. The depth to the water table is 

 75 feet. The capacity of the plant for domestic supply was 7.3 gallons 

 a minute. The corresponding drawdown was obtained and found to be 

 20 inches. On the hypothesis that the discharge is proportional to the 

 drawdown, even over a wide range, it was believed that the well would 

 yield 100 gallons a minute with a drawdown not exceeding the suction 

 limit for that moderately high altitude. The fact that the principle was 

 confirmed by the test after the new plant was installed is of interest and 

 importance. 



The limiting conditions, namely, the small bore of the well, the 

 high lift, and the low capacity, led to the selection of the Luitweiler, a 

 high-grade double-acting reciprocating puni]). The double-action is 

 obtained with heart-shaped cams in such manner that the power required 

 is constant, and the efficiency is very high. Most double-action pumps 

 are misrepresented in this particular, and are no more efficient than 

 single-action pumps. \\'hen the small domestic-supply pump was re- 

 moved it was found that the well was not straight. Consequently the 

 pump rods of the Luitweiler rub on each otiier, increasing the load. 

 Although a small engine (6-horsepower') was provided in the design, it 

 is able to pull the load satisfactorily, but the well should lie straightened 

 f^r a new one drilled at an early date. 



