64 



BULLETIN i;:>2, U. S. DEPARTMENT OF AGRICULTURE. 



For the plants having slide-valve engines, a comparison of the costs of fuel 

 for lifting an acre-foot of water 1 foot will show that the effect of the highest 

 average lift an<l the longesl run per fire up for the year 1913, which occurred 

 in the Smithport plant, has served to make the latter plant compare favor- 

 ably with the other slide-valve plants, although it is by far the poorest plant 

 of the lot. On the other hand, the effect of the lowest lift aud the shortest 

 run per fire up for the year 1013. which occurred in the Raceland plant, has 

 servei tc make it the most expensive plant per acre-foot of water lifted 1 foot, 

 although the Raceland plant is the equal of any of the other slide-valve plants. 

 The efficiency of the pumps in the plant at Poydras was increased considerably 

 by the changes made in pipes and impellers in 1913. 



The only plant operated by electricity shows a considerably higher cost for 

 power in 1914 for lifting au acre-foot of water 1 foot than do most of the 

 steam plants. However, it will he noted that the amount of pumping was small, 

 and as the relatively large monthly charge for current is a constant, whether 

 the pumps are operated or not. on years of small pumping the unit cost in 

 this plant will he high. In the first nine months of 1915 about the same 

 quantity of water was pumped as in the whole of 1914, but the fixed charge 

 was proportionately less. Therefore the unit cost was much less in 1915 than 

 in 1914. 



While a number of plants were in operation in which the pumps were driven 

 by oil-burning engines, the cost data are available only for subdistrict No. 1, 

 Raceland. However, the small unit cost for lifting an acre-foot of water 1 foot 

 is a striking feature of this plant. The unit cost for labor is high on account 

 of the small area of this district. The total charge for labor on a plant of 

 this kind need not be much more for a plant large enough to drain an area 

 several times greater. 



The amounts of rainfall and run-off on the districts given in the foregoing 

 tables are not all typical, and an average of them would not'give a figure suit- 

 able for general application. From these a selection has been made of the 

 typical figures : an average of them is as follows : Rainfall, 48.61 inches ; run-off, 

 21.56 inches; per cent of rainfall appearing as run-off. 44.4. The mean annual 

 rainfall for this section is about 56 inches, so that the amount pumped under 

 average conditions would be a depth of 24.8 inches per year. The average lift 

 for plants in this section would not be far from 5 feet. Following are the 

 average results from the various plants under actual conditions of operation ; 

 it includes only those figures which are known to be typical : 



Average results from various plants. 



Kind of plant. 



Total cost 

 of operation 

 per acre- 

 foot foot. 



Steam slide-valve engine $0. 075 



Steam Corliss-valve engine .060 



Oil engine .040 



Electric motor .097 



Cost of fuel 

 per acre- 

 foot foot. 



10.050 



.035 

 .015 

 1.072 



Total cost 



of lifting 2 



acre-feet 



5 feet. 



SO. 75 

 .60 

 .40 

 .97 



1 Cost of power. 



Since the average amount of water to be removed from drainage districts in 

 this section is about 24 inches per year, the average cost, per acre per year, of 

 operation of drainage pumping plants will be about as shown in the last column 

 of the above table. 



