Quantity of Water Consumed in Irrigation. 31 



two quantities would suffice, making the depth, say, 12 

 inches, and the quantity of water per acre about 44,000 

 cubic feet, given in four waterings, averaging 3 inches each in 

 depth. This represents the consumption under heads Sol, 

 5, and a portion of 4 (see pars. 4 and 5), and is in the main 

 supported by some results obtained a few years ago on the 

 Bari Doab canal, in the Punjab.* Colonel Baird Smith, R.E., 

 mentions that the result of several experiments made in 

 Italy, in the irrigation of meadows, gave a depth of 3J 

 inches for each watering ; other experiments gave as much 

 as 6 inches, but some of the water was available for other 

 land at a lower level.-J* Major Scott Moncrieff, RE., records 

 that 2*36 inches ('06 metre) was found by experiment to be an 

 ample depth for watering in Castile. J Many other instances 

 could hy given, more or less in support of the author's 

 figures, and some showing higher results ; but since it is 

 seldom stated at what distances the fields were from the 

 point of measurement, what was the nature of the soil, and 

 other important particulars, it is fair to conclude that the 

 higher results include considerable loss in the channels lead- 

 ing to the fields; this loss the author is endeavouring to 

 arrive at separately. 



12. In a light sandy soil more water would be consumed ; 

 but the author is decidedly of opinion that most of the in- 

 creased consumption above shown to occur in certain 

 divisions of the Ganges canal, is in the canal and distribu- 

 taries, where they pass through light soil, rather than in the 

 fields. If beds be similarly formed in two different soils, 

 the extra consumption in the lighter soil is an increase of the 

 quantity absorbed during the time each bed takes to fill. § 

 Thus, supposing a depth of 2 inches of water required in the 

 bed, and that 1 inch is absorbed in average soil before this 

 depth is attained, making 3 inches consumed ; then the in- 

 crease in a light sandy soil would be on the 1 inch, which 

 might become, say, 2 inches, making the consumption in 

 the light soil 4 inches. These figures represent, in the 

 opinion of the author, the depths of the waterings respec- 



* Professional Papers on Indian Engineering, Vol. I., new series (Koorkee, 

 1872), page 368. 



f Italian Irrigation (1855), Vol. II., pages 84, 85. 



J Irrigation in Southern Europe (1868), page 105. 



§ There are 400 or 500 beds to an acre in well irrigation, but fewer in canal 

 irrigation. Evaporation may be neglected for the short time (some three to 

 five minutes only) each of these takes to fill. 



