83 



Comparing the flow of the river during the irrigation season with the area culti- 

 vated, wc got an approximation to the average duty of water as it has been in this 

 valley during this year. It can not, however, bo said to ho a just estimate, as the 

 water was confessedly not siidiciont. A just measure of the duty of water should be 

 based on the amount that is sutliciout to furnish tiie crop the needed amount of moist- 

 ure. Much of the land this year did not receive all that was needed, and the late 

 crops were successful only because of the copious rains of August. We may take tho 

 season as from April to Septeuibtir, as the water between the first dajs of those 

 mouths was nearly all used for irrigation, much of that of April being stored and 

 used subsecjuently. In these f) months the total How was 211,811 acro-fcct, or, as the 

 area watered from the waters of the river is very nearly l:i.">,000 acres, it was equiva- 

 lent to a depth of 18.6 inches over the irrigated area. Hence, during these ') months 

 each cubic foot por second was called upon to furnish water for 196 acres. This is 

 greater than the duty when there is sufficient water, for, as stated above, much laud 

 suite red from a scarcity. 



In addition to the water from tho river, there was a rainfall which amounted to 

 9.64 inches at the college — near the exit of the river from the foothills — and of about 

 8 inches at Greeley, at the lower end of tho valley, or an average of over 8 inches from 

 the rain. The total depth of water from both sources has thou been nearly 27 inches. 



The duty of water found for tho whole district by the method above used, gives a 

 result that seems excessive to all who are intimately acquainted with this valley. 

 The method is defective inasmuch as it does not take into acgount the areas which 

 did not have sufficient water. To get tho duty of water which is practically useful, 

 wo should know the amount that would be used if the irrigator had all that he 

 needed and at the times when he needed it, and a supply scant enough to insure that 

 none goes to waste. 



Tabulated data are given for the duty of water under the Cache a la 

 Poudre Canal No. 2 (one of the oldest of the large canals on the river) 

 from May 27 to September 10, inclusive. 



For the last four days in May tho amouut flowing into the canal equals the flow of 

 1,791 cubic foot per second for one day ; in Juno, 10,425 ; in July, 6,213; in August, 

 3,186, and for the portion of September here given, 662; or for tho whole period, 

 22,277. As the How of one cubic foot per second is sufficient to cover one acre 2 

 feet deep, very nearly, or 2 acre-feet in one day, the amount of water used by this 

 canal from May 27 to September 10 was 44,500 acre-feet. As it is known with some 

 degree of accuracy that the area which depends on water from this ditch is between 

 24,000 and 25,000 acres, this flow would therefore be sufficient to cover the whole area 

 with water over 21 inches deep. If the flow during May and April bo added, this 

 depth would be increased. The rainfall also increases the depth of the water that has 

 been used on tho laud. In tho interval covered by these measures, the average duty, 

 excluding rain, is nearly 120 acres per second-foot, while for the valley as a whole it 

 is 196 acres. During tho month of June, water was used at the rate of 72 acres per 

 second-foot, assuming that all the laud was irrigated. As a matter of fact, the 

 irrigation of this month was confined almost entirely to the crops of cereals and 

 alfalfa, which occupied about two thirds of tho 25,000 acres. 



The above facts suggest that if one wishes to use the duty of water to determine 

 the amount of water he will need to water a given area, that tho average duty is very 

 misleading; and that during the period when water is wanted iu greatest quantities, 

 the duty ordinarily taken as the basis of water rights in Colorado, viz, 55 acres per 

 second-foot, is the safer guide. 



Irrigation statistics of 1890. — Tabulated estimates are given of the 

 area under ditch in Colorado, the area irrigated, mileage of canals, and 

 cost of irrigation works during 1880. Canal construction was most 

 5G08— No. 2 2 



