Page:Collier's New Encyclopedia v. 05.djvu/251

IBBIGATION 199 IRBIGATION jnstable gates by which the amount of water delivered to each furrow can be regulated. In the application of this water the attention of an irrigator is required to see that the proper amount is kept in each furrow, and that it does not break out and flood the surface, leav- ing the furrow beyond the break without moisture. The success of this system de- pends on having a soil in which vertical percolation is not excessive and lateral movement is adequate. The furrows must be so constructed as to maintain the velocity of the water within the safe limit permitted by the character of the soil; otherwise there will be an injurious erosion of the furrows. Where these conditions are secured it has several ad- vantages; it thoroughly soaks the soil and accomplishes the distribution of moisture without saturating the surface and causing it to run together, as it does where water stands on it. In cultivating crops the displacement of the soil is re- duced to a minimum; hence, the labor is reduced and the cost is less than by any method which distributes water so evenly and thoroughly. There is less loss from evaporation because a less area of water is exposed to the action of the air and sun. Subirrigation. — Introducing water be- low the surface for the watering of crops has several obvious theoretical ad- vantages, such as the preventing of loss by evaporation, distributing water at levels which will encourage plants to strike their roots deep in the soil, and the reducing of frequent surface cultivation, which have caused inventors and culti- vators to labor to secure a system which would be effective and cheap enough for general adoption, but thus far without complete success. Irrigation Laws aiid histitiitions. — In France, Spain, Italy, Egypt, and India all the more important irrigation works are owned and controlled by the govern- ment. In Italy, especially, irrigation is highly developed. Most of the water for irrigation purposes is drawn from the Po river and from lakes Maggiore and Como. In undeveloped and sparsely set- tled countries like Australia nearly all that has been done is the result of pri- vate enterprise. In Canada all streams are state property and all irrigation works are built under licenses issued by the government, and in accordance with the plans prepared or approved by it. The Reclamation Service in the United States, operated by the national govern- ment, was established by the Reclamation Act of June 17, 1902. By 1920 some 3,000,000 acres of land located in semi- arid and arid regions had been made valuable both from the standpoint of agri- culture and of homesteading. The irriga- tion projects are in Ariz., Cal., Colo., Idaho, Kan., Mont., Nebr., Nev., N. M., State Project Estimated area on comjilotion Gross cost Arizona Arizona-California California Colorado Idaho Montana Montana-North Dakota. Nebraska Wyoming Nevada New Mexico New Mexico-Texas . . . . North Dakota Oregon Oregon-California South Dakota Utah Washington Wyoming Total Salt River Yuma Orland {Grand Valley Uncompahgre Valley f Boise < King Hill I Minidoka Huntley Milk River . Sun River Blackfeet Flathead .Fort Peck Lower Yellowstone North Platte Newlands Carlsbad Rio Grande North Dakota Pumping . , Umatilla Klamath Belle Fourche Strawberry' Valley C Okanogan Yakima : ■< Storage unit Sunnysidc unit L Tieton unit f Jackson Lake enlargement -< Rivprton t Shoshone Acres 192,077 110,000 20,533 50.000 100,000 327.552 1C.385 121.392 32.885 181.000 174.620 118.500 134.500 152,000 59.613 251.715 231.000 24,991 162,000 26.151 36,300 141.444 97,889 60.000 10,099 110,828 32,000 100.000 136.618 3,212,092 Dollars 15,106.943 9,495,570 1.018,298 3.545,157 7.341,051 12,758,210 591.362 5.998,863 1,750.943 5.955,475 3,775,096 1,048,250 3.761.877 704.534 2,915.090 10,643,517 6.384.544 1,383,458 9.775.296 721.163 2,473,191 3,092,101 3,479,S02 3,506.004 947.029 3.783,105 3.355,599 3,380,284 783,153 71,918 6,109,061 135,686,549