786 



EXPERIMENT STATION RECORD. 



[Vol. 37 



Experiments on effects of temperature on evaporation and on the extension 

 of the evaporation depths fi-ora land pans to larger open water surfaces under 

 the same conditions by use of a floating pan are also reported, together with the 

 results of meteorological observations taken in connection with evaporation 

 investigations in general. 



Part 2 of the report deals with evaporation from river-bed materials. " The 

 final figures indicate that for the period of the sand-tank work the evaporation 

 from the surface of the sand from the smaller tank, approximately 2 ft. in 

 diameter, was about 7.5 per cent greater than from the larger tank. This 

 figure does not check that found for the water tanks, the corresponding differ- 

 ence there being 3.5 per cent." 



Other data of the.se experiments are graphically reported. 



Use of power and rates for irrigation pumping. G. R. Kenny {Jour. Elec- 

 tricity, S8 (1917). No. 12, pp. 496, 4'J7, fig. i).— Data on the character of electric 

 pumping plants in their relation to power rates, compiled from the practice of 

 a hydroelectric company in California, are reported. Some data from typical 

 districts on acreage irrigated and cost of power per acre are given in the follow- 

 ing table: 



Data on irrigated districta served. 



Acreage irrigated 



Horsepower used 



Acres per horsepower 



Average acres per horsepower, all classes of crops 

 Average costs per acre 



"Practically all of the pumps in use are of the direct-connected centrifugal 

 type. For the deep well pumping, the turbine and plunger types of well pumps 

 are installed. The pumping motors on the system vary in size from 3 to 75 

 horsepower, only a very few being in excess of 1.") horsepower, while the average 

 at the end of 1916 was 10.4 hnrsepowor." 



The rates used, based on the maximum demand, are given In the following 

 table : 



Rates based on maTimum demand. 



A survey of all gas engine pumping plants operating within one mile of the 

 company's lines showed that " the gas engines were used where but little irriga- 

 tion was required, when water was pumped from ditches, or where water was 

 needed to supplement ditch irrigation after the ditches ha^ gone dry. The 

 engines are generally run for only a short period each year. About 1,200 en- 



