38 IRRIGATION FARMING. 



the intake it is usually possible, owing to the greater 

 slope of the country, to reach the high lands or water- 

 sheds of the area to be irrigated with the shortest possible 

 diversion line, or that portion of the canal's course which 

 is necessary to bring the line to the neighborhood of the 

 irrigable lands. This is usually expensive and unpro- 

 ductive of immediate benefit, as it does not directly irri- 

 gate any land. The disadvantages of locating the canal 

 headworks high up on the streams are serious. The 

 country having an excessive fall requires rough hillside 

 cuttings, perhaps in rock, and the line is, moreover,- 

 intersected by hillside drainage, the crossing of which 

 entails serious difficulties. But along the great Rocky 

 Mountain foothills this objection has been entirely dis- 

 regarded, and the English or high-line canal flows through 

 the rock-ribbed South Platte canon a distance of over 

 thirty miles before it reaches the open country, where 

 the first water is delivered to patrons. When taking out 

 a ditch in a flat country, as is often the case, the work 

 is much more simple and not nearly so expensive. These 

 conditions are often observed in the prairie districts at 

 great distances from the mountains. 



The other classification of surface waters is that of 

 the catchment area or reservoir order, and is a source of 

 supply that may be termed artificial. Holdings of water 

 by this plan may be obtained without resorting to the 

 streams, by providing dams at suitable places for catch- 

 ing the storm or run-off freshets coming from rainfall on 

 a vast watershed lying back of and at an elevation above 

 the reservoir site itself. In selecting such sites, how- 

 ever, two or three cautions must be observed. In no 

 case should the water be stored in main channels. Sup- 

 pose there is a ravine running down, with side ravines 

 cutting into it and with many laterals, and with a tract of 

 ti\i or ten square miles above, which acts as a catchment 

 for waters which run down in flood or storm times. 



