The irrigating season lasts about three months. While the crops are maturing during part of May, June and July, they will receive two or three waterings, and in early September the hay lands are again watered in order to start the growth of grass before the frosts.
In case all the surplus water of a given stream is stored, the duty of that stream will be increased by the amount of water now flowing to waste during the remaining nine months, and as a portion of this time is the flood period, owing to the melting of the snows in the mountains and to the spring rains, this storage water will increase the duty of the stream at least five-fold; that is, five times as many acres may be irrigated by the stream as at present, provided that storage capacity can be found for all of its waste waters.
In considering the duty of a stream it must be remembered that there is a great loss of water by seepage through the sides of a canal and evaporation from its surface, between the headworks and the irrigated lands, this loss may amount to from 25 to 35 per cent., according to climate, soil, and the length and cross-section of the canal.
PRESENT STATE OF IRRIGATION—PROGRESS AND LAWS.
The earlier stages of irrigation development are better illustrated in Montana than in any other State in the Union.
There irrigation practice and laws are exceedingly crude and remain so chiefly because of the abundance of water, and the ease and facility with which it can be diverted to the land; as a consequence of this latter fact the laws were framed in the most liberal spirit, declaring right of eminent domain, acknowledging the right of priority in appropriating the waters, and further stating, that any person having a ditch leading to irrigable lands may use the waters of the territory for irrigation.
The latest law, framed in 1885, is a very slight improvement; it requires persons appropriating water, to post the usual notice in a conspicuous place; to file with the county recorder a notice of appropriation, with names and proper description of place, stream, etc., and that work must be commenced within forty days of the posting of the notice and be prosecuted with due diligence until completed.
Persons who have heretofore acquired title to the use of water, may within six months from the passage of this law file a statement of the above facts in the office of the recorder, but failure to do this shall not forfeit his rights.
Provision is made for the measurement of water, using that very uncertain and elastic unit, the miner's inch, and defining the same.
The difficulties arising under these laws will be appreciated, when I state that it is impossible to construct a rating flume that will measure the number of inches of water flowing in a large stream, by the method provided in the law.