CROP ROTATION AND IRRIGATION 119 



of certain essential facts and conditions. Among these are 

 existing water supply, quantity required to grow crops, losses 

 from seepage and evaporation in distribution, character of the 

 control over streams already vested, and measures of adminis- 

 tration requisite for an equitable and effective division of water 

 supply among a multitude of users. Such unforeseen results 

 as alkali lands and seepage waters, formerly secondary consid- 

 erations, are now often the most primary problems. Such irri- 

 gation as could easily be accomplished with simple means inde- 

 pendent of co-operative institutions has largely been effected. 

 As the work extended, greater problems arose, claims became 

 hopelessly conflicting and united effort under institutional ad- 

 ministration became an imperative condition of advantageous 

 development. 



Water Supply. There are two sources of water for irriga- 

 tion: Surface waters, such as streams and lakes, and subter- 

 ranean waters. The former supply over 90 per cent of the 

 irrigated land. There are three ways of obtaining underground 

 waters: By pumping from wells; by driving tunnels into the 

 sides of hills and mountains; and by using flowing wells. Ar- 

 tesian areas are widely scattered, and individually they are of 

 small size, except in the Dakotas and California. In 1889, 

 51,896 acres, or 1.4 per cent of the irrigated land, were irrigated 

 from wells. In 14 irrigating states there were 8,097 wells, near- 

 ly half of which were used in irrigation. Each well supplied 

 on an average 13 acres, had a depth of 210 feet and discharged 

 54 gallons per minute; 169,644 acres were irrigated from wells 

 in 1899. Underground waters seem to be present very gener- 

 ally. It is claimed that there is not a farm of 160 acres upon 

 the great plains region without the requisite moisture absolutely 

 needed for from 10 to 30 acres of tillable ground. 1 The aver- 

 age depth of water applied to crops in 1899 was 4.35 feet, and 

 in 1900, 4.13 feet. 



Application to Crops. The two principal methods of irriga- 

 tion are by flooding and through furrows. The former is gen- 

 erally used in growing grain. There are two methods of 

 flooding, the check system and by wild flooding. By the latter 

 process a level field is completely submerged. When the ground 

 is not level enough for this, the field is divided into compart- 

 1 Hiaton, Kept, on Irriga., Cong, serial No, 2899, part I, p. & 



