1904 



FORESTRY AND IRRIGATION 



45; 



region contained 375 square miles of 

 artesian water-bearing lands, distributed 

 through a number of basins that is, 

 artesian conditions existed under ap- 

 proximately one-sixth of the "valley 

 lands which could be made tillable and 

 productive by the application of water. 

 In addition, there were large areas bor- 

 dering the artesian belts in which the 

 ground water lay near enough to the 

 surface to be accessible by pumps of 

 various sorts and in some districts these 

 have been extensively utilized for irri- 

 gation. 



The principal of the artesian basins 

 are those of the Coastal Plain, Chino, 

 San Bernardino, and San Jacinto, with 

 approximate original areas of 295, 24, 

 30, and 14 square miles respectively. 

 The water supplied by each of these has 

 been extensively drawn upon during the 

 past decade, the heaviest drafts being 

 from the Coastal Plain and the San Ber- 

 nardino sources. In the former case the 

 waters supply the towns of the coast, 

 and are used for the diversified crops of 

 citrus and deciduous fruits, alfalfa, wal- 

 nuts, grapes, and celery, which are 

 raised there. The underground San 

 Bernardino waters supply the towns of 

 San Bernardino, Colton, and Riverside, 

 are used for local irrigation within the 

 San Bernardino valley, and are the prin- 

 cipal source from which the splendid 

 Riverside colony draws its supply for 

 irrigation. 



These subterranean sources have been 

 most extensively developed within the 

 past ten years. Practically all the acre- 

 age added to the irrigated districts within 

 that time have been through the addi- 

 tion of artesian or pumped waters to 

 the surface supply. These same years 

 have on the whole been years of low 

 rainfall in southern California, just as 

 the previous decade, during which these 

 developments began, was one ot high 

 rainfall. Under the combination of 

 heavy withdrawals of ground waters 

 and a shortage of the rain, which is 

 depended upon to recharge the subter- 

 ranean reservoirs, these have declined 

 notably. As a result, the original area 

 f 375 square miles of artesian lands 

 has shrunken 33 percent, to 250 square 

 miles. Pressures and vield in wells 



which are still flowing have notably de- 

 creased, the ground- water level outside 

 the artesian belts has declined, and a 

 feeling of uneasiness pervades some of 

 the irrigating communities as to the per- 

 manence of their supply. On the whole, 

 the subterranean reservoirs must be re- 

 garded as resisting the drafts upon 

 them remarkably well. The summer 

 waters which once flowed from the moun- 

 tain canyons out upon the valley washes, 

 where they promptly sank and added 

 their volume to that of the stored un- 

 derground supplies, have been appropri- 

 ated and are used for irrigation. The 

 proportion of them that escapes direct 

 evaporation from the soil and indirect 

 evaporation by transpiration through 

 the plants varies with soils and irri- 

 gation practice, but must on the whole 

 be small. This small residue alone 

 is now added to the underground re- 

 serves, where formerly nearly all of the 

 summer flow contributed. The storm 

 \vaters of the winter season have always 

 been the chief factor in filling the sub- 

 surface gravels, and these are still avail- 

 able in greater part, although a few 

 storage reservoirs, like that of Hemet 

 and Bear Valley, intercept flood waters, 

 a part of which, were they not thus in- 

 tercepted, would be absorbed on their 

 way to the sea by the gravels. These 

 are factors which have diminished the 

 .annual accessions to the underground 

 supplies, although, if the communities 

 as a whole are considered, storage of 

 flood waters must be considered most 

 economical engineering, since it un- 

 doubtedly diminishes the total loss 

 through excessive floods. It is only 

 from the special point of view of the 

 companies or communities immedi- 

 ately dependent upon the saturated 

 bodies of gravel for a supply that this 

 storage can be considered disadvan- 

 tageous. On the other hand, with the 

 partial drainage of the gravels their 

 absorptive capacity is increased, and 

 in consequence a larger proportion of 

 the flood waters must be taken up as 

 they flow across the valleys than be- 

 fore. Actually, therefore, by drawing 

 heavily upon the underground reser- 

 voirs, the amount of water which is 

 lost in floods is decreased, and the total 



