24 



BULLETIN" 1026, U. S. DEPAKTMElSrT OF AGRICULTURE. 



DUTY OF THE RIVER. 



The average available supply of water in the Cache la Poudre 

 amounts to 375,000 acre-feet, which includes the normal flow of the 

 river and its tributaries and 35,000 acre-feet of foreign water, but 

 does not include the seepage return to the river. Applied to the 

 225,000 acres irrigated in the valley it gives for the stream, as a 

 whole, a duty of 1.67 acre-feet per acre; or, expressed differently, 

 each second- foot of the average annual discharge irrigates 434 acres. 

 This high general duty is made possible only by the large percentage 

 of the flow held in storage for use at critical times and by the large 

 amount of return seepage which is used several times over again. 





1916 





1917 



140000 

 120000 

 100000 



t- 



Ll 



U aoooo 



L 



u 



g 60000 

 40000 



eoooo 







z 



IT 



I 



a 

 < 



>< 



z 



1 







< 



1- 



u 

 



> 







z 



Q 





I 



LI 



L 



1 



or 









a. 



1- 

 u 







>0 



z 







u 

 a 





z 

 < 



U 



a 

 < 



I 



a 



- -> 







 < 



U 

 (0 



u 

 



z 







u 



Q 





z 



1 



HI 



u 



L 



z 



a 

 < 



>< 



1 





u 



< 



U 

 ID 



u 







> U 



ou 



ZQ 































































































































































































































































































i 



























- 























































































































































































































































































































































































































































































































































































































































































































































































































1 















1 



























1 













R 



1 



1 



■ 



e 



1 





a 



1 



1 



I 











i 

















■ 



1 



I 







a 



9 



1 

























s-torage; DinccT 





STORAGEl DIRElC-r 



Fic 



3. — Diversions from tlie Caclie la Poudre River for storage aiid for 

 direct irrigation compared for the 2 years of the Investigation. 



THE CONSUMPTIVE DUTY. 



The water actually consumed, or the consumptive duty, may be 

 arrived at by considering in addition the water which passes into 

 the South Platte River from the Cache la Poudre Eiver, Lone Tree 

 Creek, and various canal wasteways dumping into the South Platte 

 or Crow Creek. In 1916 the available supply exclusive of seepage 

 return Avas 336,000 acre-feet, and 79,000 acre-feet passed out of the 

 valley. The net consumption of 257,000 acre-feet on the 218,000 acres 

 irrigated that year gives a duty of 1.18 acre-feet per acre. In 1^17 

 the supply was 608,000 acre-feet, and 309,000^ acre-feet passed into 

 the South Platte. Tlie net consumption of 299,000 acre-feet on the 

 225,000 acres irrigated that year gives a duty of 1.33 acre-feet per 

 acre. As the water supply during 1916 was slightly below normal 



' Partly eslimated. 



