lEEIGATION IN NORTHERN COLORADO. 69 



RESERVOIRS. 



The settlement of the Cache la Poudre Valley proceeded very 

 rapidly after 1870 and the consequent extension of irrigation soon 

 brought out the necessity for reservoirs. ■ The stream was over-ap- 

 propriated and as the irrigated area under early canals increased, the 

 later canals suffered more and more from shortage of water. Con- 

 ditions under the older canals became acute when continuous grain 

 cropping had exhausted the land and the farmers were compelled 

 to turn their attention to more profitable crops such as alfalfa, po- 

 tatoes, and later, sugar beets. These crops required irrigation later 

 in the season when water was available for only a few small ditches 

 with early priorities. To meet these conditions the construction of 

 reservoirs became general and has continued until nearly all the culti- 

 vated land of the valley is supplied to some extent with stored water. 

 This is clearly shown in Plate XV, given to afford a comparison 

 between the total area irrigated in 1916 and the area which received 

 reservoir water that year. 



With reference to organization, the reservoirs of the valley may be 

 divided into 3 classes. The largest class is made up of small private 

 reservoirs built by the individual to make the best use of a small head, 

 to free himself from the limitations imposed by rotation periods, or 

 to save a few acre-feet for a late irrigation. The second class includes 

 the reservoirs which are owned as a part of a canal system and 

 store water to be distributed as a part of the general supply. The 

 majority of the reservoirs of this class belong to either the North. 

 Poudre Irrigation Co. or the Water Supply & Storage Co. The 

 canals owned by these companies were constructed in 1881 and 1882 

 and as it was realized from the start that a sufficient supply of water 

 could not be obtained by direct appropriation the construction of 

 reservoirs was begun immediately. The third class includes the reser- 

 voirs owned by cooperative companies and supplying water to stock- 

 holders under canals which act as common carriers. Usually there 

 is no legal connection between the reservoir company and the canal 

 company, but in many cases a majority of the stockholders of the 

 two companies are identical. 



Reservoirs in the valley are supplied by natural streams ; by seep- 

 age from canals, irrigated land, and other reservoirs; and by run- 

 off from some normally dry catchment area during torrential rains. 

 The great majority of the larger reservoirs take their supply from 

 the Cache la Poudre and its tributaries, but a number are also sup- 

 lied wholly or in part with foreign water. With the extension of 

 irrigation, seepage from canals, reservoirs, and irrigated lands be- 

 comes important as a source of supply and many small reservoirs are 

 now almost wholly dependent upon it. Only a few reservoirs are de- 



