316 IRRIGATION INVESTIGATIONS IN CALIFORNIA.. 



soil, often accumulate in undesirable quantity. The extent to which lands in the 

 delta region of Kings River have through this cause been deteriorating is often 

 remarked, but as yet no steps seem to have been taken to correct the evil. Manj- 

 examples of such deleterious effect upon the soils are found on the north side of the 

 river as well as on the south. 



Near Fresno, where the original holdings of land were small and where the 

 quantity of water available for irrigation was also small in proportion to the demand, 

 it was quite natural that unusual effort should have been made to thoroughly prepare 

 the land for irrigation before applying the water. It became customary to subdivide 

 fields into small, rectangular tracts, often onh' one-quarter acre or less in area, and 

 to make the surface of those tracts perfectly smooth and level. Each rectangular 

 plat of ground was surrounded by a low embankment, and irrigation was effected by 

 flooding its surface. Irrigation was complete as soon as water covered the entire 

 plat. An}^ excess of water was allowed to sink into the soil. During the first years 

 of irrigation near Fresno, while the soils and subsoils were verj- dry and ground 

 water was at depths of from 30 to 60 feet below the surface, the quantity of water 

 absorbed was sometimes far in excess of what would ordinarily be considered pos- 

 sible. Five feet of vertical depth were occasionally applied at a single irrigation. 

 The quantity of water put upon a single plat during a season would occasionally be 

 equivalent to a depth over all of 20 feet. This system of flooding in small rectangu- 

 lar tracts was gradually modified to a sj^stem of furrow irrigation. Furrows were 

 also used to a considerable extent in irrigating grain land and orchards, irrigation in 

 such cases being effected by turning the water into deep plow furrows which, accord- 

 ing to the amount of surface fall of the ground, were carried in a direction of greatest 

 slope, or quartering across the same in cases when velocities along lines of greatest 

 slope would cause too great erosion. To some extent the method of irrigating in 

 contour checks came into use, but it has not found general favor, the irrigating heads 

 being general^ too small to use this system to advantuge. The application of water 

 to land commences each season in March, or as soon thereafter as the canals are well 

 supplied with water. At this time water is applied to grain lands, to orchards, and 

 to vineyards. The irrigation of alfalfa usually begins a month later. One irrigation 

 is ordinaril}' considered ample for orchards and vineyards, but when spring rains are 

 scant and the soil has not been thoroughl}^ wet by winter rains, irrigations are 

 repeated if water is available. Alfalfa is generallj^ irrigated once for each crop cut, 

 the number of waterings it receives per year being generally 3 to 5. Very little 

 grain land is irrigated by application of water to the surface. This is generally done 

 only when it appears possible thereby to save a crop which it was hoped would 

 mature without irrigation. 



The large volume of water which is annually diverted from Kings River and 

 sinks, from the many irrigation canals and from branches and the small irrigating 

 ditches and through soils flooded into the subsurface strata, has gradually' saturated 

 the suDsoils and brought the ground water so near the surface of the ground that it 

 has become necessary in many localities to construct works for drainage. Numerous 

 examples of this kind can be cited. A notable example is in the region to the east 

 and south of Fresno. Drain ditches 4 to 6 feet deep have now replaced the irrigaticjn 

 ditchea from which a few years ago water was spread over the surface of the ground. 



