340 Irrigation and Drainage 



systems of flooding, whenever it is possible to estab- 

 lish and maintain the best conditions for them, and 

 there is no other system which permits of so uni- 

 form a wetting of the surface. 



There are two fundamentally different systems of 

 flooding. One covers the surface of a field with a 

 thin sheet of running water, maintained until the 

 desired saturation has been reached ; the other covers 

 the surface with a sheet of standing water, which is 

 allowed to remain until the soil has absorbed enough, 

 when the balance is drawn off ; or, simply as much 

 water as is desired is placed upon the land, and this 

 remains on the surface until it is absorbed. 



The two systems are used most for crops like 

 the small grains, grasses and clovers, which closely 

 cover the ground, and where intertillage is not practiced. 

 They are also used extensively where fields for any crop 

 must be moistened preparatory to plowing and seeding. 



Flooding by running water is practiced with great 

 nicety and thoroughness on large fields of 40, 80 and 

 even 160 acres in the old Union Colony at Greeley, 

 Colorado. Here, usually, the natural slope of the 

 country is good, and a distributing ditch is carried 

 along the highest edge of a field to be irrigated. 

 When the time for watering has arrived, the field is 

 divided into lands of 60 to 120 feet by parallel fur- 

 rows, made by using a wide V-shaped plow, throwing 

 the earth both ways, thus forming distributing fur- 

 rows, represented in Fig. 84, about 30 inches wide at 

 the top. These furrows are made rapidly with a 3- 

 or 4 -horse team, and when a crop of grain is ready 



