186 EXPERIMENT STATION EECOED. 



Ground water for irrigation in the Sacramento Valley, California, K. 

 Bbyan {U. 8. Geol. Surrey, Water-8ui)ply Paper S75-A (1915), pp. IV +49, pis. 

 2, figs. 6). — This report, prepared in cooperatiou with the department of 

 engineering of the State of California, describes the geography and geology and 

 deals with the ground water resources of an area in California containing 15 

 per cent of the agricultural land of the State, with reference to their develop- 

 ment and use for irrigation. 



"The valley includes (1) sloping plains, (2) shallow basins of heavy soils, 

 (3) low ridges of loam and silt soils along the rivers, and (4) higher plains of 

 older alluvium laid down during a previous cycle of deposition and now raised 

 above the valley floor in low hills and rolling plains, . . . Throughout the val- 

 ley the alluvium at a depth of a few feet is saturated with water. . . . The 

 water table slopes from the sides of the valley toward the center and from the 

 north to the south. The grade is slightly less than that of the land surface, so 

 that water is shallower in the basin area than toward the hills. . . . 



"Although there are large areas in the valley with a shallow water table, 

 favorable to evaporation and the accumulation of alkali, only comparatively 

 small areas are unfitted for agriculture from this cause." This is explained as 

 follows: (1) The ground waters are of good quality. ... (2) The water 

 table is very flat over the basins, and movements of the ground water are slug- 

 gish. Water is supplied more freely at the bases of the slopes, and for this 

 reason the principal concentration of alkali occurs at the edges of the basins. 

 This is particularly, the case on the west side, where alkaline patches and areas 

 of salt grass border the basin along its western edge. ... (3) The heavy win- 

 ter rains leach out much of the salts concentrated at the surface. Similarly 

 flood waters wash out the salts in overflowed lands, and on the edges of the 

 plains the same waters deposit mud or sediment, which often covers up the 

 alkali." 



The fluctuations of the water table are said to be large. " The total quantity 

 of ground water in the valley is very great. The sands and gravels contain 

 from 20 to 40 per cent of water, the clays perhaps more. Because the pore 

 spaces of the sand and gravel are much larger than those of the clay the rate 

 of flow through these materials is much greater and they become for practical 

 purposes the water bearers. The sand and gravels are distributed through the 

 alluvium, which thickens from less than 50 ft. at the edge of the valley to 500 

 ft. or more in the center. . . . 



" Observations show that pumping produces only a local depression of the 

 water table, and that the winter rise in normal years is rapid and effective. 

 General lowering of the ground water may be expected in the summer, and it 

 will be large during periods of deflcient rainfall. Heavy pumping may be ex- 

 pected to create still further depression, which, if the whole valley were irri- 

 gated by pumping, would increase the general lowering. ... In view of the 

 high lifts common in southern California, where water is being pumped for 

 irrigating alfalfa with a lift of 100 ft. and for irrigating citrus fruits with a 

 lift of 200 to 400 ft., it would seem that a Very considerable increase in the 

 Dumber of plants can be made in the present pumping districts of the Sacra- 

 mento Valley. . . . Although it is possible from geologic evidence to determine 

 for any part of the valley the general distribution and character of the water- 

 bearing beds, the precise location of these beds and their value as sources of 

 water can be determined only by sinking wells." 



Considerable general information is given relating to well sinking and the 

 pumping and distribution of irrigation water. 



Statistics of ground water irrigation in the valley gathered by the author 

 indicate that there are 1,6G4 pumping plants irrigating a total area of 40,859 



