688 EXPERIMENT STATION RECORD. 



probably not exceed 10 per cent of the water applied; the evaporation loss, 

 where the crops will permit deep furrow Irrigation and cultivation, will prob- 

 ably not exceed 15 per cent of the water applied; the surface run-off loss or 

 waste can be eliminated. The total losses for these conditions will be about 

 27 per cent." 



Flood flows, W. E. Fuller (Proc. Amer. Soc. Giv. Engin., 39 {1913), No. 5, 

 pp. 1011-106/f, pis. 5, figs. (5). —The object of this paper is (1) to present a study 

 of the frequency of floods, (2) to show the relation between the catchment 

 area and the magnitude of the flood, and (3) to present formulas and tables to 

 serve as an aid to judgment in estimating the probable maximum flood to be 

 expected on a river. 



It is concluded from this study that although flood flows on different rivers 

 vary greatly some of the characteristics of the rivers affect the floods in sub- 

 stantially the same manner throughout the country. The effect of the size of 

 the catchment area on the flood flows throughout the country is much the same 

 and this relation may be represented approximately by the expression, 

 Q (Ave.)=G A 0-8 in which Q {Ave.) equals the average yearly flood in cubic 

 feet per second, C equals a coefficient which is constant for the river at the 

 point of observation, and A equals the catchment area of the river in square 

 miles. The relation between the maximum rate of flood flow on a stream in a 

 period of years and the maximum rate of flow for 24 hours during the same 

 period may be represented approximately by the expression Q {Max.) = 

 Q (1+2A0-3), in which Q {Max.) equals the maximum rate of discharge of a 

 flood, and Q equals the greatest average rate of flow for 24 consecutive hours 

 during a period of years. On streams throughout the country, " floods which 

 are a certain ratio of the average yearly flood" occur with much the same 

 frequency, and, on the average, the probable maximum flood in a period of 

 years may be represented by the expression, Q=Q {Ave.) (l-fO.S log. T) ; 

 " Coeflacients may be obtained for streams by utilizing the foregoing relations 

 to discount the effect of the length of period of observation and the size of the 

 catchment area; these coefficients will serve as a gage for the flood-producing 

 capacity of the streams; and the difference in value of these coefficients is 

 caused by the various physical characteristics of the river and its catchment 

 area, such as storage, soil conditions, etc., and by the difference in the prevailing 

 rainfall conditions." 



The storage of flood waters for irrigation: A study of the supply available 

 from southern California streams, A. M. Strong {Proc. Amer. Soc. Civ. Engin., 

 39 {1913), No. 5, pp. 955-978, figs. i5).— Investigations on the quantity of flood 

 water being wasted in southern California, and on that part of the waste which 

 may be economically diverted, and stored for use during an entire irrigation 

 season, are reported. 



Run-off records of the San Gabriel River for two seasons show that if it 

 were possible to obtain storage for the excess run-off available for diversion 

 at an expense warranted by its value, it would be possible to double the area 

 now irrigated from the surface flow of the river. 



There are said to be many small streams in southern California similar to 

 this river, a large part of whose floods may be economically handled. Under 

 the assumption that storage facilities are economically available, it is con- 

 cluded that a diversion capacity of 2.25 second-feet per square mile of drainage 

 area will assure sufficient supply for a reservoir storage of 200 acre-feet for 

 each square mile, irrigating 40 acres, which at 2 cts. per inch per hour would 

 warrant an expenditure of $13,250 per square mile of drainage area. Similarly, 

 there would be available for increasing the underground storage a supply 

 sufficient to irrigate 45 acres. 



