24 
BULLETIN 1026, V. S. DEPARTMENT 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 
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STORAGE DIRECT 
STORAGE DIRECT 
FH 
3.— Diversions from the Cache la Poudre River for storage and for 
direct irrigation compared for the 2 years 1 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 Eiver 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 was 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 1917 
the supply was 608,000 acre-feet, and 309,000 7 acre-feet passed into 
the South Platte. The 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 estimated. 
