388 EXPERIMENT STATION RECORD. [Vol. 38 



This will depend, however, on local costs for excavation and pumping 

 machinery. 



" In determining the proper combined capacity of the pumping plant and 

 reservoir the main factor to be considered is the amount of rainfall in an 

 assumed period for which provision is to be made. ... As the accompanying 

 curves were prepared with data from storms which occurred when the land 

 was wet, a determination has been made of the proportion of storms which 

 occur when the land is wet. Of all the storms of over 2 in. in 24 hours which 

 have occurred on the districts during the time covered by the records, 64 per 

 cent occurred on a wet and 36 per cent on a dry surface; of all storms over 

 4 in. the percentages are 54 per cent and 46 per cent, respectively. Of course, 

 the storage capacity of the land influences the run-off from the small storms 

 relatively much more than it does that from the large ones. However, an 

 examination of the daily rainfall and pumping records will show that heavy 

 rains on a dry soil do not make very heavy demand on the pumping plant. It 

 is believed, therefore, that a reduction of about 30 per cent in the average 

 frequency of storms could be made safely and that the resulting figure would 

 be the proper one for use. If the character of operations that are to be con- 

 ducted on the land of a given district is known, a decision can then be made 

 as to the heaviest storm for which provision must be made. On a district 

 where staple crops are to be raised it would be economical to allow a certain 

 amount of flooding oftener than would be advisable on land where high-priced 

 truck crops are to be raised, while in residence districts it would be very 

 desirable to prevent all surface flooding. In addition to the damage to crops 

 due to flooding, there are other factors to be considered, such as inconvenience 

 to residents and the possible depressing influence on land values of floodings 

 occurring even at infrequent intervals." 



Effect of pumping from a shallow well on the ground-water table, W. W. 

 Wetb (f7. S. Dept. Agr., Jour. Agr. Research, 11 {1911), No. 7, pp. 339S57, figs. 

 16). — Experiments conducted at the Kearney Park farm under the supervision 

 of the California Experiment Station, in cooperation with the Office of Public 

 Roads and Rural Engineering of the U. S. Department of Agriculture, are re- 

 ported on the effect of pumping from a shallow well on the ground-water table 

 and its relation to the drainage of irrigated lands. 



" The results of this experiment lead to the conclusion that under soil, irri- 

 gation, and farming conditions such as are found on the Kearney Park . . . 

 tract pumping from a shallow well does not lower the ground-water table suffi- 

 ciently to afford drainage to any considerable area. In this experiment, al- 

 though the water table in the sump was maintained at a depth of about 12 ft. 

 below the ground surface and from 5 to 7 ft. below the normal ground water, 

 the effect of the pumping was not appreciable beyond 100 ft. from the pump. 

 Except within a very short distance from the pump, the ground water rose to a 

 point as near the ground surface in 1915, while the pump was in operation, as 

 it did in 1914, when no pumping was done. Seasonal variations are great 

 enough to account for any differences observed. 



" Contrary to the results obtained here, it has been found that the water 

 lable can be materially lowered by the use of tile drains for greater distances 

 away from the drain than is shown in this experiment. . . . The fact that 

 tile drains have proved more efficient than pumping from a well in lowering the 

 ground-water table is due, no doubt, to the much larger area reached by the 

 tile. . . . Thus, with such a system any lateral movement of water is more 

 readily intercepted, and any vertical pressure is relieved at more points than 

 is possible where tile is not used, even though the water table is maintained at 

 a greater depth in the well than is done by the tile lines. It would appear, 



