82 



THE IKRIGATION AGE. 



structed by the receiver, known as the Dredge El Cen- 

 tro. This was placed between the concrete gate and 

 the river to remove deposits and bars forming above 

 the headgate. Ever since 1910 these dredges have 

 been operated in the main canal and records show 

 that, during the year 1913, 903,000 cubic yards of silt 

 were pumped from the main canal by means of these 

 two dredges. 



This solved the silt question, as far as the main 

 canal and intake were concerned, but trouble was ex- 

 perienced in the smaller lateral canals, which had to be 

 kept open at great expense. The solution of this was 

 finally worked out by the use of small dredges operated 

 from the bank to clean these smaller canals. 



The smaller dredges are of two kinds, known as 

 the Stockton and Austin Dredges. They are run on 

 planks laid along the banks of the canals, and move 

 forward as the dredges work down stream. They 

 deposit the material excavated on the opposite bank 

 by means of dipper excavators or endless elevators. 

 Both types of dredges have done the work successfully, 

 but at a slightly different cost. 



Imperial Water Company No. 1, which irrigates 

 more than 100,000 acres, is the largest sub-company, 

 which takes water from the main canal in the capacity 

 of consumer.. There are also many smaller companies 

 taking water for an area aggregating approximately 

 two and one-half times as much as the territory irri- 

 gated by Imperial Water Company No. 1. Even with 

 this, not much more than one-half of the irrigable area 

 in Imperial valley is at present under cultivation, as 

 there are approximately 500,000 acres in the United 

 States, which will ultimately be irrigated from the 

 Colorado river in the Imperial Valley. 



So far as the silt question in the main and lateral 

 canals of the Imperial Valley are concerned, it may be 

 stated, that these methods have satisfactorily solved it, 

 and it is now possible to operate the system economi- 

 cally and without interruption in service. Since all 

 the dredges work while water is flowing through the 

 conduits, the serving of water continues, while the 

 canals are cleaned, and the remaining portion of the 

 silt carried by 

 the water is de- 

 posited on the 

 land. This 

 amount is vari- 

 able, depending 

 upon the extent 

 to which the ve- 

 locity in the 

 canal is d e- 

 creased before 

 the water is de- 

 livered to the 

 land. 



Ordinari 1 y 

 it may be said 

 that, if the mean 

 velocity of the 

 water flowing in 

 the canals is 

 three feet per 

 second, or more, 

 no appreciable 

 amount of silt is 

 deposited. But 



it is impossible to maintain this velocity, owing to the 

 varying demands for water, and the necessity for 

 checking the flow, in order to make deliveries. This 

 is given as a good average, but the growing and irriga- 

 tion season in Imperial Valley continues throughout 

 the whole year, which makes a great deal of difference, 

 because the silt content of the Colorado river varies 

 in different months. 



The injury from silt in the irrigation system has 

 been neutralized by dredging, which has been carried 

 on at a much lower cost than was originally expected. 

 Now remains the problem of overcoming the deposits 

 of silt in the river channel itself, which are likely to 

 occur to such an extent, that it will again overflow into 

 Lake Imperial. 



The bed of the river below Hanlon's Heading, 

 where the water is diverted for Imperial Valley, varies 

 greatly in width and the velocity at various points 

 shows wide fluctuations. Under these conditions silt 

 is continuously deposited, and the tendency of the flow 

 is to shift away from points in the channel, which have 

 thus been raised by silting. 



The Reclamation Service has done much in re- 

 cent years to maintain the channel as uniform as pos- 

 sible, but being interested in the Arizona side, on which 

 the Yuma project is located, this made it natural for 

 them to do more for the purpose of preventing the 

 j-iver from making incursions into Arizona than into 

 California. However, the work of the Reclamation 

 Service on the Arizona side has been of a very bene- 

 ficial character. 



The receiver of the California Development Com- 

 pany, bankrupt owner of the Imperial Valley water 

 system, has devoted much of his energy and resources 

 to protecting Imperial Valley since the closing of the 

 break in 1907. The resources and facilities, however, 

 have been insufficient to properly handle the situation, 

 and in 1910 the Colorado river left its channel, going 

 into Bee river, and has since flowed continuously into 

 Volcano Lake. 



After filling Volcano Lake to the level of the outlet 

 into Hardy's Colorado, the water flowed through this 

 ancient channel into the Gulf of Lower California. 

 Volcano Lake is situated at the terminus of Bee 



river, one of the 

 former channels 

 of the Colorado. 

 It is a large ex- 

 tent of flat coun- 

 try made by de- 

 posits of silt in 

 a portion of the 

 former gulf to 

 its present level 

 of approximate- 

 ly 25 feet above 

 sea level. This 

 lake has two 

 outlets, one be- 

 ing New river 

 flowing into Im- 

 perial Valley 

 and terminating 

 in Lake Imperial 

 and the other 

 being Hardy's 

 Colorado, flow- 

 ing in an oppo- 

 site direction in- 



Preparing rice field for cultivation in Hawaii. 



